User manual EAW SMAART V6

v.6 FOR MICROSOFT WINDOWS® AND MAC OS® X SOUND SYSTEM MEASUREMENT, OPTIMIZATION AND CONTROL SOFTWARE USER GUIDE Manual written and edited by Calvert Dayton and Rob Wenig. Manual design by Rob Wenig. Cover design by Martin Lindhe. ©2007 EAW Software Company, Inc. All rights reserved worldwide. No part of this publication may be reproduced, transmitted, transcribed, stored in a retrieval system, or translated into any language in any form by any means without written permission from EAW Software Company, Inc. EAW Software Company, Inc. One Main Street Whitinsville, MA 01588 Phone: (508) 234-9877 Fax: (508) 234-6479 web: http://www.eaw.com e-mail: info@eaw.com EAW Smaart 6 Operation Manual Table of Contents Chapter 1: Getting Started............................................................................................9 1.1 Hardware Requirements ............................................................................9 1.1.1 1.1.2 1.1.3 1.1.4 1.1.5 1.2 Computer.....................................................................................9 Measurement Microphone ........................................................11 Microphone Preamplifier ..........................................................11 Cables and Interconnections .....................................................11 Additional Useful Equipment ...................................................11 Smaart 6 Software Installation ................................................................12 1.2.1 First Time Installation...............................................................12 1.3 1.4 Smaart 6 Signal I/O .................................................................................14 Introduction to the User Interface............................................................16 1.4.1 1.4.2 1.4.3 1.4.4 1.4.5 1.4.6 1.4.7 1.4.8 1.4.9 1.4.10 The Menu Bar ...........................................................................17 The Plot Area ............................................................................17 Cursor Readout .........................................................................17 Start/Stop Buttons .....................................................................17 Measurement Mode Buttons .....................................................18 Display Controls .......................................................................18 Reference Trace Controls..........................................................18 Signal Generator .......................................................................19 Internal Delay Control ..............................................................20 Signal Level/SPL Display and Input Level Meters ..................20 1.5 How to use this Manual...........................................................................21 Chapter 2: Concepts, Glossary, and Bibliography.......................................23 2.1 Concepts ..................................................................................................23 2.1.1 2.1.2 2.1.3 2.1.4 2.1.5 2.1.6 2.1.7 2.1.8 2.1.9 Decibels.....................................................................................23 Fast Fourier Transform .............................................................24 Averaging..................................................................................25 Sampling Rate ...........................................................................25 Frequency Resolution ...............................................................26 Pink and White Noise ...............................................................27 Data Window Functions............................................................28 Impulse Response .....................................................................29 The Transfer Function...............................................................29 iii EAW Smaart 6 Operation Manual 2.1.10 2.1.11 2.2 2.3 Coherence..................................................................................30 Signal Alignment ......................................................................30 Glossary of Terms ...................................................................................31 Selected Bibliography .............................................................................34 Chapter 3: Analysis Modes and Display Types ...............................................37 3.1 Spectrum Measurements .........................................................................38 3.1.1 3.1.2 3.1.3 3.2 RTA ..........................................................................................38 Spectrograph .............................................................................40 Spectrum Measurement Parameters..........................................41 Frequency Response Measurements........................................................44 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 3.2.6 3.2.7 3.2.8 Basic Frequency Response Measurement Setup.......................44 Frequency Response Overview.................................................45 The Magnitude Display.............................................................45 The Phase Display ....................................................................46 Time Windowing ......................................................................46 Averaging and Smoothing ........................................................47 Coherence and Coherence Blanking .........................................49 Magnitude Thresholding ...........................................................51 3.3 Delay and Impulse Response Measurements ..........................................52 3.3.1 3.3.2 3.3.3 Impulse Response Measurement Parameters............................52 Working with Impulse Response Data......................................54 Automatic Delay Locator..........................................................55 3.4 SPL Measurements..................................................................................56 3.4.1 3.4.2 The Signal Level/SPL Readout.................................................56 Calibrating to SPL.....................................................................57 3.5 Capturing and Loading Measurement Data.............................................60 3.5.1 3.5.2 3.5.3 3.5.4 Capturing a Reference Trace.....................................................60 Loading a Reference Trace .......................................................61 Working with Reference Traces ...............................................61 Averaging Reference Traces .....................................................62 3.6 3.7 3.8 Internal Delay ..........................................................................................63 Internal Signal Generator ........................................................................63 Weighting Curves....................................................................................65 iv EAW Smaart 6 Operation Manual 3.9 External Device Control ..........................................................................66 3.9.1 3.9.2 External Device Control Interface ............................................66 Configuring External Devices...................................................67 3.10 3.11 The Locked Cursor ..................................................................................68 Smaart 6 Screen Capture .........................................................................69 3.11.1 3.11.2 Windows ...................................................................................69 Mac OSX...................................................................................69 Chapter 4: Applications.................................................................................................71 4.1 Real-Time Spectrum Analyzer (RTA) ....................................................72 4.1.1 4.2 Connecting the Measurement System.......................................72 Measuring an Analog Equalizer ..............................................................74 4.2.1 4.2.2 Measurement Setup...................................................................75 Adjusting Signal Levels ............................................................75 4.3 Measuring a Loudspeaker........................................................................77 4.3.1 4.3.2 4.3.3 Adjust Signal Levels .................................................................78 Impulse Response Measurement...............................................79 Frequency Response Measurement of the Loudspeaker...........80 4.4 4.5 Measuring a Loudspeaker and Setting an Equalizer ...............................81 Measuring and Optimizing a Sound System ..........................................84 Chapter 5: Smaart 6 Commands ..............................................................................91 5.1 File Menu.................................................................................................91 5.1.1 5.1.2 5.2 Save Impulse .............................................................................91 Exit ............................................................................................91 External Devices Menu ...........................................................................91 5.2.1 5.2.2 Add New Device.......................................................................91 Remove Device .........................................................................93 5.3 Options Menu ..........................................................................................93 5.3.1 5.3.2 5.3.3 5.3.4 5.3.5 5.3.6 Spectrum ...................................................................................93 Frequency Response .................................................................95 IR Analysis................................................................................97 Audio I/O ..................................................................................98 Delay .........................................................................................99 Zoom .......................................................................................101 v EAW Smaart 6 Operation Manual 5.3.7 5.3.8 5.3.9 5.4 Instantaneous...........................................................................101 Reseed Averages .....................................................................102 High Contrast View ................................................................102 Help Menu .............................................................................................102 5.4.1 5.4.2 About.......................................................................................102 Smaart Help.............................................................................102 5.5 Keyboard Shortcuts ...............................................................................103 Chapter 6: Troubleshooting......................................................................................105 6.1 Installation Problems .............................................................................105 6.1.1 6.1.2 6.2 Problems During Installation ..................................................105 Problems After Installation .....................................................105 Configuring Audio Input/Output Controls ............................................106 6.2.1 Windows Wave (Wave-in/Wave-out) Devices Only..............106 6.3 6.4 6.5 6.6 6.7 Sound Hardware Problems ....................................................................107 Performance Issues................................................................................108 Font and Display Problems ...................................................................108 Restoring the Default Configuration .....................................................109 Technical Support Information..............................................................110 Index ..............................................................................................................111 vi EAW Smaart 6 Operation Manual List of Figures 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8 1-9 1-10 2-1 2-2 3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-9 3-10 3-11 3-12 3-13 3-14 3-15 3-16 3-17 4-1 Audio I/O tab of the Options dialog ..................................................................................14 Input levels: too low (left), correct (middle), and too high (right) ....................................15 Smaart 6 main window ......................................................................................................16 Menu bar ............................................................................................................................17 Cursor readout....................................................................................................................17 Display mode (left) and Measurement mode (right) buttons.............................................18 Capture and Load buttons ..................................................................................................18 Signal Generator and Delay controls .................................................................................19 Signal Generation dialog ...................................................................................................19 Signal level, SPL, and input meters ...................................................................................20 Pink noise graphed on octave band (left) and narrowband logarithmic (right) scales.......27 White noise graphed on octave band (left) and narrowband logarithmic (right) scales ....27 View and plot display after clicking the Spectrum button.................................................37 Impulse Response Window ...............................................................................................38 Spectrograph display..........................................................................................................40 Spectrograph dB Range .....................................................................................................41 Frequency Scale list ...........................................................................................................41 Average options (left); Weight options (right) ..................................................................42 Block Diagram of a Frequency Response Measurement...................................................44 Coherence Blanking parameters in Frequency Response tab of Options dialog ...............50 Block Diagram of a Delay or Impulse Response Measurement ........................................52 Impulse Response window ................................................................................................53 Delay auto-locator buttons.................................................................................................56 Units/Options button at the top of the Signal Level/SPL Readout ....................................57 SPL/Calibrations Options and Amplitude Calibration dialogs..........................................59 Legend dialog ....................................................................................................................61 Data Information dialog.....................................................................................................62 Delay Presets in Impulse Response window .....................................................................63 Signal Generation dialog ...................................................................................................64 RTA measurement setup....................................................................................................72 vii EAW Smaart 6 Operation Manual 4-2 4-3 4-4 4-5 4-6 4-7 4-8 4-9 4-10 5-1 5-2 5-3 5-4 5-5 5-6 5-7 5-8 5-9 Default RTA spectrum display (1/12th-octave).................................................................73 Spectrum parameters..........................................................................................................73 Spectrograph and SPL displays .........................................................................................74 Analog EQ measurement setup..........................................................................................75 Signal Generation screen control (left) and dialog (right) .................................................76 Sample measurement of an analog parametric EQ filter ...................................................77 Speaker/amp measurement setup.......................................................................................78 Impulse response of a small loudspeaker in a room ..........................................................79 Setup to measure and equalize a loudspeaker....................................................................81 Selecting from External Devices->Add menu (left) and configuring the device (right) ...91 Selecting (left) and configuring (right) a newly added external device input ...................92 Spectrum tab in Options dialog .........................................................................................93 Frequency Response tab in Options dialog........................................................................95 IR Analysis tab in Options dialog......................................................................................97 Audio I/O tab in Options dialog ........................................................................................98 Delay tab in Options dialog ...............................................................................................99 Zoom tab in Options dialog .............................................................................................101 About screen ....................................................................................................................102 viii EAW Smaart 6 Operation Manual Chapter 1: Getting Started Since its initial introduction in 1996, Smaart® has firmly established itself as the most comprehensive and widely used software product in the pro audio industry for real-time sound system measurement, optimization, and control. Smaart performs dual-channel, FFT-based audio measurement in an intuitive, accessible interface that integrates measurement, analysis, and data logging. Smaart 6 has been rebuilt from the ground up in a modern, object-oriented architectural design. This significant architectural upgrade enables increased measurement power, and cross-platform operation. Smaart 6 now runs native under Mac OSX and Windows XP from the same unified source code. A decade of user input has been integrated with EAW's innovations to enhance and streamline the user interface. Smaart 6 can also remotely control an extensive, constantly expanding list of professional equalizers and DSP processors. 1.1 1.1.1 Hardware Requirements Computer Laptop computers are most convenient for portable field operation. The computer running Smaart 6 must meet these minimum specifications: Windows Configuration · · · · · · Operating System: Windows 2000 or XP (or higher). CPU: 1 GHz or faster Intel Pentium or compatible. RAM: 512 MB to 1 GB Video: AGP or PCI Express Graphics card with at least 32 Mb RAM. Display: 1024 x 768 pixel display device with 24/32-bit colors. Sound Hardware: Windows-compatible (Wave/WDM or ASIO) with stereo line level input, 16-bit/44.1 kHz to 24-bit/96 kHz sampling with full-duplex (simultaneous play and record) capability. Macintosh Configuration · · · · · · Operating System: Mac OS X 10.4 (Tiger) or higher. CPU: Apple Macintosh family CPU with minimum 1 GHz or faster G4, G5 or Intel microprocessor. RAM: 512 MB to 1 GB Video: AGP or PCI Express Graphics card with at least 32 Mb RAM. Display: 1024 x 768 pixel display device with 24/32-bit colors. Sound Hardware: Apple Core Audio compatible with stereo line level input, 16-bit/ 44.1 kHz to 24-bit/96 kHz sampling with full-duplex (simultaneous play and record) capability. 9 EAW Smaart 6 Operation Manual Getting Started Computer Sound Hardware Smaart does not address computer sound hardware directly. Since audio data is obtained through platform-native or third-party audio APIs, Smaart should work with virtually any audio I/O device compatible with the Windows and Mac operating systems. Since only the A/D and D/A functions of the computer's sound hardware are actually used, Smaart 6 works well with a wide variety of computer audio input devices including off-the-shelf sound cards for desktop machines and the built-in sound hardware in many notebook computers. External hardware with USB, PCMCIA, and Firewire interfaces, some combining high-quality A/D and D/A converters with mic preamps, are convenient for field use. Two independent external line-level input channels (sometimes found as one stereo connector) are required for transfer function and impulse response measurements. The sound hardware must be capable recording and playing simultaneously to use Smaart's internal signal generator as the stimulus signal source for measurements. We do not recommend using the microphone inputs on computer sound cards for measurement applications. Instead, use an external mixer or microphone preamp to route the microphone to the computer's line-level inputs. Smaart 6 makes no use of the sound hardware's synthesis capability. The relevant factors that differentiate sound hardware for Smaart 6's applications are the maximum sampling rate, sampling resolution (bits per sample) and signal-to-noise ratio (S/N). If your computer does not have sound hardware, lacks a line-level input, or its existing hardware is problematic for any reason, there are many devices available for audio I/O. The following features and audio characteristics are important: · · · · · Simultaneous play and record (full duplex) capability Two independent, external, line-level input channels 16- to 24-bit sample resolution Digital inputs for use with external A/D converters (optional but recommended) User-selectable sampling rates: Smaart 6 supports sampling rates from 5512 Hz to 96 kHz. Audio input devices used with Smaart 6 must support at least one of Smaart's primary sampling rates: 44.1k, 48k, or 96k (samples/second). 10 EAW Smaart 6 Operation Manual Getting Started 1.1.2 Measurement Microphone A measurement microphone is necessary to measure anything other than an electronic device. Since the measurement mic must accurately convert acoustical pressure into voltage, we recommend an omnidirectional mic with the flattest possible frequency response. Condenser microphones are most commonly used for measurement applications. These require phantom power, either from the mic preamp or an internal battery. A microphone calibrator is also required to perform calibrated sound pressure measurements. 1.1.3 Microphone Preamplifier A mic preamp may be required to interface with the measurement mic. It should have a low noise floor with sufficient gain to drive the computer's line input(s) at a useful level. The preamp must include phantom power if a condenser mic is used. Those who prefer a small mixer, routing device, or FOH console instead of a dedicated mic preamplifier, make sure to disable all processing (EQ, dynamics, etc.) on the channels used to drive the measurement system inputs. 1.1.4 Cables and Interconnections Use only professional-quality cables, adapters, and interconnections to interface the measurement system with the equipment being measured. If your sound card has threeconductor 1/8-in stereo connectors, we recommend using breakout cables to convert to 1/4-in phone or XLR connectors. Y-cables are useful for tying the measurement system into sound systems. Also, as most sound cards use unbalanced (2-conductor) inputs, several sets of adapters that allow balanced to unbalanced connections may be necessary. 1.1.5 Additional Useful Equipment The following equipment may be required depending on the types of measurements you wish to make: Mixer/Level Adjustment Device Although relative signal levels can be set at the computer in many cases, it is helpful to adjust signal levels externally. Being able to quickly switch the signals reaching the sound card's inputs can greatly expedite the measurement process. A compact mixer with quiet microphone inputs and built-in phantom power is ideal. Microphone Calibrator and/or Sound Level Meter To make accurate Sound Pressure Level (SPL) measurements with Smaart 6, the program must be calibrated using an external reference. The most accurate way to calibrate to SPL requires a piston microphone calibrator. Calibrating Smaart 6 to SPL can be done fairly accurately with an SPL meter as a reference if a microphone calibrator is not available. A high quality sound pressure level meter with an audio output can also be an effective measurement microphone. 11 EAW Smaart 6 Operation Manual Getting Started 1.2 Smaart 6 Software Installation Respect the License Agreement Notice that when you install EAW Smaart 6, the installation requires you indicate your acceptance of the terms of the End User License Agreement. In doing so, you are agreeing to be legally bound by the terms of this agreement. We strongly encourage you to read the End User License Agreement and we want to emphasize the following: EAW Smaart 6 is licensed on a single-user or, in the case of multi-station site license, a single-station basis. That means that each single-user copy or single-station installation can be used legally by one person on one machine at any one time. The Smaart 6 installation and copy protection mechanisms are intended to help enforce this restriction. They are not intended to create any sort of hardship for licensed users or prevent any legitimate use of the software. If you need to install Smaart 6 to a second machine for your own use (e.g., on both your office machine and the notebook you computer you use in the field), that is perfectly permissible. Simply perform the initial installation on the second machine as you did on the first and register the installation at my.eaw.com to obtain a keyfile to permanently unlock it. If you require additional installations for additional users, any Smaart 6 license can be converted to a multi-user site license that allows adding workstations at a reduced price as needed. 1.2.1 First Time Installation Installing Smaart 6 on any computer for the first time is a two-stage process. The initial installation installs a temporary, 30-day copy of Smaart 6 to enable immediate use. Permanent installation of Smaart 6 requires a keyfile created by EAW specifically for your machine. The installation program should start automatically (Mac and PC) upon inserting the installation CD. If the installer does not start automatically, open the CD and doubleclick the Setup program icon. NOTE: We strongly recommend closing and/or disabling all programs before installing Smaart 6, particularly anti-virus and/or system monitor software. 1. When the first dialog appears, click Unlock Now to proceed with registration. Click Continue to use Smaart during the 30-day trial period. Click Purchase Smaart to buy a copy if this is a demo version. You will be routed to our website to purchase the software and then proceed with installation. To register later, initiate the process from the About dialog. To access the About dialog on Mac OS X, select About Smaart under Smaart on the shared system menu bar. In Windows, choose Help->About Smaart. 12 EAW Smaart 6 Operation Manual Getting Started 2. If you have Internet access from this computer, click Unlock Online (this example). Otherwise, click Unlock with Keyfile to obtain the necessary information from another computer that can connect to our website. Be sure to copy the Machine Number before going to the other computer. Enter your existing EAW account information or create a new account. This will enable you to log onto my.eaw.com and view your Smaart installation information. This is very useful if you need to reinstall Smaart. Click Unlock Now. 3. 4. When the installation process has completed, restart your computer if prompted to do so, otherwise you can begin using Smaart 6. If you experience problems during or after installation, see Chapter 6: Troubleshooting. 13 EAW Smaart 6 Operation Manual Getting Started 1.3 Smaart 6 Signal I/O This section discusses how to recognize your hardware and adjust signal levels. 1. 2. 3. Make sure your computer recognizes your sound card. Connect any external audio devices. Start Smaart 6. Do not disconnect an external audio device while Smaart 6 is running. 4. Select the proper audio input and output device(s) and channel(s) by choosing Options->Audio I/O. The Options dialog appears with the Audio I/O tab selected (Figure 1-1). Figure 1-1 Audio I/O tab of the Options dialog 14 EAW Smaart 6 Operation Manual Getting Started 5. Select input and output devices from the Input Device and Output Device area's Device drop-lists, respectively. The drop-lists displays your soundcard's inputs/ outputs and those of any connected external I/O devices already added. Select the desired input channels for your measurement and reference signals from the Meas in and Ref In drop-lists. Typical assignment for a stereo input device is Meas In = Left, Ref In = Right. Select the channel(s) to use for output signals from the Main and Aux lists. Select the desired input and output resolution values from the Input/Output Device Bits Per Sample menus. Resolution values can be 16, 18, 20, 24. Connect devices to the outputs/inputs of your soundcard or external preamp, and Smaart 6 correctly handles the signals. 6. 7. 8. 9. Many soundcards use internal circuitry to mix several audio streams together to the master output, or to select and/or mix the signals presented to the sound card inputs. These options may need to be configured for your card to enable line-level input and wave output. Launch the Windows mixer application by pressing Alt+V on the keyboard. The signal generator defaults to a low level to prevent equipment damage, overload to input levels, and hearing discomfort. This level, in conjunction with the output levels and mixer settings for your device, determines the sound card output level. Figure 1-2 Input levels: too low (left), correct (middle), and too high (right) Overall input levels should be between ­12 and ­6 dB for most measurements. The input levels must be adjusted to avoid clipping the sound card's A/D converters while maintaining a high signal to noise ratio. When Smaart 6 is running, the input level meters indicate the soundcard's A/D converters peak input levels. If the levels are two high, the clipping indicators light and the input level must be reduced to perform accurate measurements. If your computer has both microphone and line level inputs, be sure to avoid sending a line level signal to a microphone input. We recommend avoiding using the microphone inputs on most computer sound hardware because their preamp circuitry typically does not approach the quality of even very modestly priced mixers. Also, a small mixer manages multiple measurement input signals and offers other advantages, such as phantom power. 15 EAW Smaart 6 Operation Manual Getting Started 1.4 Introduction to the User Interface The Smaart 6 interface is designed to put the most frequently used functions for most sound system optimization applications within a single mouse-click. Almost everything in the main program window functions as a control. The readout fields for the primary measurement and display parameters are drop-lists that display available options when clicked upon. Clicking on the signal generator or SPL readout opens their setup dialogs, and the delay control pops up a dialog for entering an exact delay time when clicked. Clicking and dragging with your mouse on any plot zooms its x- and y-axes on the area selected. Each graph can be assigned any data type with a single button click. Even the input level meters perform dual functions, bringing the corresponding signal trace (measurement or reference) to the top of the RTA display when clicked. To the right of the plot area in the main real-time program window are two groups of display controls for the two primary measurement types: Spectrum and Frequency Response. Clicking the Spectrum or Freq. Resp. buttons invoke a split window display with the associated chart types for each: Spectrograph and RTA (Spectrum), Phase and Magnitude (Frequency Response). Clicking the small arrowhead buttons on the right of the Spectrum or Freq. Resp. buttons open their tab of the Options dialog. Main display options for each are grouped together with their shortcut buttons. The rest of this section introduces Smaart 6's user interface. See Chapter 5: Smaart 6 Commands for detailed descriptions of menus and settings. Figure 1-3 Smaart 6 main window 16 EAW Smaart 6 Operation Manual Getting Started 1.4.1 The Menu Bar Smaart's most frequently used functions and commands are available as on-screen controls or keyboard shortcuts. Pull-down menus in the Menu Bar provide an alternate method of selecting many of these same functions, in addition to providing access to some less frequently used features. Figure 1-4 Menu bar A menu command followed by "..." opens a dialog box. An arrowhead to the right of a menu item indicates a sub-menu that appears to the right when selected. 1.4.2 The Plot Area The largest section of the Smaart 6 program window is the Plot Area, used for all of Smaart 6's primary data displays. See Chapter 3: Analysis Modes and Display Types for more information. 1.4.3 Cursor Readout The cursor readout above the plot area provides numeric values for the location of the mouse tracking cursor (white cross in Figure 1-5) in amplitude/magnitude, frequency or time, and phase, depending on the current display. When a Locked Cursor is present, its coordinates are also shown here, along with the delta between the locked and moveable cursors (page 68). Figure 1-5 Cursor readout 1.4.4 Start/Stop Buttons In all real-time operating modes, clicking the Start button starts the Smaart 6 analyzer and begins plotting data. The Start button turns to Stop during a measurement. Press Stop to stop the measurement and view the display. 17 EAW Smaart 6 Operation Manual Getting Started 1.4.5 Measurement Mode Buttons The Measurement mode buttons provide one-click access to Smaart's three primary measurement types: · · · Spectrum: See Spectrum Measurements on page 38. Freq. Resp.: See Frequency Response Measurements on page 44. IR Analysis: See Delay and Impulse Response Measurements on page 52. Figure 1-6 Display mode (left) and Measurement mode (right) buttons 1.4.6 Display Controls The RTA, Spectrograph, Magnitude, and Phase buttons at the top of the Plot Area (left of Figure 1-6) display different information based on the same input data. Although the buttons at the top of the plot remain the same, Capture, Load, and Legend are disabled in Spectrograph display. 1.4.7 Reference Trace Controls Figure 1-7 Capture and Load buttons The Capture and Load buttons store and display RTA, Frequency Response, and Phase traces, respectively. See Capturing and Loading Measurement Data on page 60. 18 EAW Smaart 6 Operation Manual Getting Started 1.4.8 Signal Generator Figure 1-8 Signal Generator and Delay controls Click the button to activate the signal generator; the square indicator on the button illuminates green when active. To configure the signal generator: 1. Click the arrow to the right of the Signal Generator button (labeled with the current signal generator type). The Signal Generation dialog opens. Figure 1-9 Signal Generation dialog 2. 3. 4. 5. 6. Select a Signal type and specify the signal level(s). Specify the frequency for a sine wave (Freq1) or two frequencies (Freq1 and Freq2) for a dual sine wave if applicable. Use the spinner buttons to the right of the Level1 field (and Level2 if Dual Sine is selected) to set the signal level, or type a value into the text field. Turn on the Signal Generator by selecting the Generator ON checkbox. Click OK to close the dialog. 19 EAW Smaart 6 Operation Manual Getting Started 1.4.9 Internal Delay Control The Delay control (Figure 1-8) provides access to Smaart 6's internal signal delay. The internal delay can provide up to 750 ms of delay (in 0.01 ms increments) for one of the two input signals, intended primarily to provide signal alignment for Frequency Response measurements. The delay selected and corresponding distance are displayed on the Delay control. To alter delay times by the increments specified in the Delay tab, use the up and down arrow buttons to the right of the readout field. Or, click the Delay readout and enter the desired delay time directly. Auto Delay Locator Buttons The Auto Sm and Auto Lg buttons (Figure 1-8) activate Smaart 6's Automatic Delay Locator using the small or large time window preset, respectively. See Automatic Delay Locator on page 55 for more details. 1.4.10 Signal Level/SPL Display and Input Level Meters Figure 1-10 Signal level, SPL, and input meters The Signal Level/SPL Display provides a numeric readout of the overall signal level for the selected SPL Source channel (see Audio I/O on page 98) and can be calibrated to provide SPL readings. The input level meters display the levels of the two input signals relative to the maximum input voltage (regarded as 0 dB) for the A/D converters on the selected input device. Each meter includes a clip indicator that lights if the input signal level exceeds the A/D converter's maximum input voltage. Click the Mea Sig and Ref Sig to show/hide the corresponding signal on the RTA display. 20 EAW Smaart 6 Operation Manual Getting Started 1.5 How to use this Manual EAW has dedicated substantial time and resources to the Smaart 6 documentation. We recognize that our customers comprise a diverse range of experience and have strived to write and organize this manual to be accessible to everyone. Of course it is more fun to use Smaart 6 than read about it but we are confident that your time spent reading this manual will be rewarding. Manual Structure Those experienced with Smaart 6 can use the manual as a reference and look up subjects as needed. However, the manual is structured to be read sequentially and anyone who wants to get the most out of Smaart would likely benefit from doing so at least once. The manual contains the following chapters: · · Chapter 1: Getting Started discusses hardware requirements, software installation, and introduces the user interface. Chapter 2: Concepts, Glossary, and Bibliography introduces the concepts and terminology necessary to understand how to use Smaart 6. It includes a Glossary (page 31) and Bibliography (page 34). Chapter 3: Analysis Modes and Display Types discusses Smaart 6's measurement modes and displays in detail. Chapter 4: Applications presents examples of Smaart 6's most essential applications. Chapter 5: Smaart 6 Commands discusses all menu commands including all of the Options dialog parameters. Chapter 6: Troubleshooting discusses common problems encountered and procedures to diagnose and fix them. · · · · Keyboard Shortcuts Ctrl/Cmd means press the Control (Ctrl) key if you are using Windows, or the Command key (sometimes referred to as the "Apple" or "Flower" key) on a Mac. Similarly Alt/Opt refers to the Alt key on a Windows keyboard or the Option Key on a Mac. LeftClick refers to a Windows style two-button mouse and is equivalent to a regular mouse click on a Mac. See Keyboard Shortcuts on page 103 for a complete list. 21 EAW Smaart 6 Operation Manual Getting Started How to Use the PDF The Portable Document Format (PDF) version of this manual is a valuable learning tool, providing effective online help while using Smaart 6. We have included some useful amenities to aid your learning and exploration process. NOTE: We assume Windows users will use Acrobat Reader and Mac users either Acrobat or Preview. · The Bookmarks, displayed to the left of the main document in Acrobat or on the right in Preview, serve as a continuously visible table of contents.The Bookmark headings are collapsed when the document is first opened. Click on a subject heading to jump to that page. Click the "+" (Windows) or " " (on Mac) to expand that heading to show subheadings. To collapse an expanded heading, click the "­" (Windows) or " " (on a Mac). The manual's Table of Contents and List of Figures entries are active links to their pages. Select the hand cursor, move it over the heading until it turns into a finger, then click to navigate to that page. Be aware that some headings are active only over their number not the heading text (i.e., List of Figure entries). All cross references are active links. Move the hand cursor over the reference until it turns into a finger and click to follow the reference. Use the left and right Navigation arrow keys to go back and forth between views. This is a great method to follow a cross reference or check out a Bookmark and return to the page from which you were reading. Use the Find function as an index on the fly that is as effective as the real index on page 111. To search for a keyword, press Ctrl+F (Windows) or Cmd+F (Mac; Cmd is the Apple key). Use the magnifying glass tool or the zoom edit box on the top bar to zoom in/ out. This is helpful when examining a complex graphic or setting the text size for easier reading. · · · · · · 22 EAW Smaart 6 Operation Manual Chapter 2: Concepts, Glossary, and Bibliography This chapter defines the concepts and terminology used in Smaart 6. These definitions are accurate with regard to Smaart 6 but are not intended to be mathematically comprehensive. A bibliography is provided at the end of the chapter for those wishing to pursue a more rigorous study of these topics. 2.1 2.1.1 Concepts Decibels The decibel (dB) is a unit that expresses the logarithmic ratio between two amounts of power, voltage, or any two values that differ over a wide range. Logarithmic scales are useful in acoustics and audio because of the wide range of human hearing sensitivity to sound pressure and frequencies. Most audio measurements based on voltage or sound pressure are expressed in decibels. The power and voltage ratios in Table 2-1 illustrate why a logarithmic scale is needed. Table 2-1 Power and voltage ratios as decibels Power Ratio .1 .5 1 2 10 100 1,000 10,000 100,000 1,000,000 dB -10 -3 0 3 10 20 30 40 50 60 Voltage Ratio .1 .5 1 2 10 100 1,000 10,000 100,000 1,000,000 dB -20 -6 1 6 20 40 60 80 100 120 Note that 60 dB, about half the decibel range of human hearing, represents a Power Ratio of one million to one. A frequent point of confusion regarding decibels is the meaning of 0 dB. For SmaartLive's purposes, 0 dB means: · In a Frequency Response measurement, dB values represent the difference between the reference and measurement input signals. When the energy in both input signals at a given frequency is the same, the magnitude response is 0 dB at that frequency. 23 EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography · At frequencies where the measurement signal has more energy than the reference signal, the transfer function is a positive dB value; when the measurement signal has less energy, the value is negative. With respect to the input level meters and the default Full-Scale calibration reference, 0 dB (or 0 dBFS) means the maximum possible output of the A/D converter on the selected input device. All lesser amplitude/magnitude values are displayed as n dB down from this maximum. · 2.1.2 Fast Fourier Transform The Fast Fourier Transform (FFT) is a special case of Discrete Fourier Transform (DFT), a mathematical technique used to calculate the frequency-domain representation of a finite length, time-domain data series. The output of a Fourier Transform is a set of complex numbers representing the frequency and phase of the original time series. An FFT is referred to as a Fast Fourier Transform because it uses mathematical shortcuts to greatly reduce the computation time required to calculate a DFT. This technique requires that the time-domain data series used in the FFT contain a power of two number of samples (i.e., 2n samples, where n is an integer). All Smaart 6 frequency transformations are FFTs that require the time record to be 2n samples in length. Table 2-2 Powers of 2 n 8 9 10 11 12 2n 256 512 1024 2048 4096 NOTE: It is certainly possible to calculate the Fourier Transform of a time record with an arbitrary number of samples. However, when the number of samples is not a power of 2, the additional calculations required on a PC can become very large, sometimes resulting in a very slow Fourier Transform. 24 EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography 2.1.3 Averaging When using asynchronous test signals such as music or random noise in FFT measurements, it is often beneficial to average data from a number of FFT frames. Averaging over a number of FFT frames: · · · increases the likelihood of having sufficient energy at all frequencies for a meaningful measurement (particularly with music); makes the overall frequency content of a dynamic signal easier to see; helps minimize the influence of possible sources of error that might affect a single FFT measurement. Nearly all Smaart averaging is based on RMS averaging, aggregated either linearly (all frames contribute equally to the averaged result), or exponentially (more weight given to the most recent, than to older data). Linear averaging is also sometimes referred to as artithmetic averaging. Smaart offers linear averaging options from 1 (no averaging) to 128 frames. There is also a linear infinite averaging option that keeps a running average while the analyzer runs (or until you Reseed the averaging buffer). The Fast and Slow averaging options, available for Spectrum and SPL measurements, are exponential averages. 2.1.4 Sampling Rate The sampling rate is the number of amplitude samples taken per second from an analog audio signal to create a digital waveform. The most important thing to remember about sampling rate is that it limits the highest measurable frequency. The highest frequency that can be accurately represented in a digital waveform is equal to half of the sampling rate. This limit is often referred to as the Nyquist frequency, after Harry Nyquist who first proved its existence in the course of his work on improving the speed and carrying capacity of telegraph and teletype systems in the early 20th century. If frequencies in excess of the Nyquist frequency are present in a signal when it is digitized, they become aliased or wrapped around and incorrectly added in at lower frequencies. For this reason, a high-order low pass filter with its corner frequency near the Nyquist limit is normally applied to audio signals before they pass through an A/D converter. The practical implication of this anti-aliasing filter is that it further limits the highest measurable frequency at a given sampling rate, typically to about 90% of the Nyquist frequency. Compact discs run at a standard sampling rate of 44.1 kHz. Professional digital audio recording machines sample in the range 48-96 kHz. Computer sound cards commonly have several user-selectable sampling rates such as 48, 44.1, 22.05, or 11.025 kHz. Smaart 6 determines the available sampling rates by polling your computer's sound hardware each time it launches. The fastest sampling rate supported by Smaart 6 is currently 96 kHz. 25 EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography 2.1.5 Frequency Resolution The frequency resolution (Q) of an FFT is equal to the sampling rate divided by the FFT size. The frequency data points in an FFT are distributed linearly along the frequency axis at intervals of Q Hz, from 0 to the Nyquist Frequency (1/2 the sampling rate). For example, with a sampling rate of 44.1 kHz, an FFT size of 4096 (4 k) yields a frequency resolution of 10.77 Hz. The resulting FFT has a data point every 10.77 Hz, 0-22.05 kHz. Fixed-Point Per Octave (FPPO) Frequency Response Display One problem associated with the linear distribution of FFT data points arises from the fact that we hear frequencies logarithmically. Human hearing perceives each doubling of frequency as an equal interval so each higher octave contains twice as many frequencies as the one below. Using the example discussed on the previous page, in an FFT with a frequency resolution of 10.77 Hz, there will be only three data points in the range 31.563 Hz (the center frequencies of the two lowest octaves), providing very poor resolution. In the two highest octaves, the span between the center frequencies (8-16 kHz) is 8 kHz, yielding more than 700 data points. When viewed using a logarithmic frequency scale, these data points are densely packed, creating a very difficult display to interpret. Smaart 6 addresses this problem by using multiple FFTs, at different sampling rates and FFT sizes, then combining the results to provide equal resolution in every octave, except the two lowest. The resolution of the Real-time mode display is 24 points per octave above 44 Hz, with 24 points distributed over the two lowest octaves. Note that using multiple FFTs results in a longer time window at lower frequencies and a shorter time window at higher frequencies. Frequency Resolution and Octave/Fractional Octave Band Displays For Spectrum measurements, the multiple-FFT technique used to measure Frequency Response is not an option due to a mathematical limitation and so all RTA displays are created from single FFTs. Since the linear distribution of FFT points in a single FFT yields lower resolution in the lower than higher octaves, there may be bands at the low end that contain only 0 or 1 data point, depending on the display and FFT input parameters. The wider spacing between FFT data points in the lower octaves accounts for the missing teeth seen at the low end in banded displays on some FFT-based analyzers. Smaart uses an advanced algorithm to properly distribute energy into bands at low frequencies but very sparse FFT data limits its effectiveness. Therefore, it is still advisable to select FFT parameters that provide good frequency resolution at the lowest frequencies required. 26 EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography 2.1.6 Pink and White Noise Pink and white noise both contain random (or pseudorandom) broadband energy. They are commonly used as signal sources in audio measurement applications. Pink Noise Pink Noise has equal energy in each octave band when averaged over a period of time. This means that when pink noise is displayed on an octave band plot, its spectrum appears flat. When its spectrum is plotted on a narrowband display, however, it appears to rolloff, or decrease in energy at the rate of -3 dB per octave (Figure 2-1). ­20 ­20 Octave Scale ­30 ­30 Logarithmic Scale (Narrow Band) Decibels ­50 Decibels 32 63 125 250 500 1K 2K 4K 8K 16K ­40 ­40 ­50 ­60 ­60 ­70 ­70 20 100 1K 10K 22K Frequency (Hertz) Frequency (Hertz) Figure 2-1 Pink noise graphed on octave band (left) and narrowband logarithmic (right) scales White Noise White noise has equal energy for each frequency when averaged over a period of time. This means that when white noise is displayed in narrowband resolution, its spectrum appears flat. However, because each successive octave band has twice as many Hz, white noise plotted on an octave band display appears to increase 3 dB in energy for each successive octave (Figure 2-2). ­20 ­20 Octave Scale ­30 ­30 Logarithmic Scale (Narrow Band) Decibels ­50 Decibels ­40 ­40 ­50 ­60 ­60 ­70 32 63 125 250 500 1K 2K 4K 8K 16K ­70 20 100 1K 10K 22K Figure 2-2 White noise graphed on octave band (left) and narrowband logarithmic (right) scales 27 EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography Choosing a Noise Source The distinction between pink and white noise is not important in Frequency Response measurements. The transfer function compares the two input signals over a given frequency range point-by-point. This is a concern when looking at a single channel RTA noise measurement. If it appears flat in narrow band resolution, it is white. If it appears to be slopping down to the right on narrow band resolution (loss at high frequencies) it may be pink. NOTE: White noise is often used to test electronic components but has so much high frequency energy that it can easily damage loudspeakers if played at high levels. For this reason we DO NOT recommend using white noise as a test signal for sound system measurement applications. 2.1.7 Data Window Functions Data window functions are commonly used to reduce truncation errors that arise from segmenting random signals into FFT-size chunks. The FFT is a circular function that assumes the signal segment being transformed is infinitely repeating. Therefore, discontinuities between the data near the beginning and end of the time domain data series can result in an excessively high noise component and leakage of data at all frequencies into neighboring frequency bins when the FFT of the signal is taken. Data window functions help alleviate this problem by attenuating the samples nearest the beginning and end of the time record being transformed before the FFT is performed. Although this technique can dramatically reduce the impact of discontinuities, there are several trade-offs involved in determining the precise shape of the attenuation curve. A number of data window functions, with various strengths and weaknesses, have been developed over the years. For most audio applications, window functions with Gaussian tapers work best. We recommend using the default Hanning window (also called a Hann window) unless you have a specific reason to use a different type. 28 EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography 2.1.8 Impulse Response An impulse response is the response of a system under test (SUT) to an impulsive stimulus. The SUT could be an electronic device, a sound system and/or an acoustical environment. In Smaart the impulse response is the time-domain representation of the system's transfer function, or system identification. For our purposes, this means a signal that describes the changes a known test signal undergoes as it passes through the SUT. The impulse response contains a wealth of information about the SUT including its propagation delay and frequency response. For an acoustical system, it also contains information about reflections, reverberation, and decay. NOTE: It is actually possible to use the impulse response of a room/system as a filter to convolve a dry signal, such as speech or music, and hear exactly what it would sound like if played through that same system in that room and heard at the measurement position. 2.1.9 The Transfer Function All frequency response (Phase and Magnitude) and impulse response data in Smaart 6 rely on a mathematical calculation called a transfer function. The transfer function compares a reference signal to a measurement signal, typically the input and output of a device/system under test (DUT/SUT), such as an equalizer, sound system, or room. Smaart 6 uses the transfer function calculation in both Frequency Response and Impulse Response measurements. Transfer function calculations are always performed in the frequency domain using FFT data. The results of the calculation are displayed in either the frequency or time domain, depending on Smaart 6's display mode. The Frequency Response display plots transfer function results in the frequency domain to show the magnitude and phase of the SUT. In Impulse mode, Smaart 6 calculates the transfer function using data from very long FFTs, then transforms the result back into the time domain to show the impulse response of the SUT. These two types of Frequency Response measurements are complementary. The reference and measurement signals must be aligned in time to obtain a valid frequency response measurement. The impulse response measurement is used to find the delay time between the two input signals. 29 EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography 2.1.10 Coherence The coherence for any two FFT frames The Smaart 6 Coherence display represents a complex mathematical function used to determine the coherence between the two signals. Smaart displays coherence values as a percentage from 0-100, rather than as a number from 0-1 because we have found that many people find it more convenient to think of it as a score than as a probability. The coherence for any two FFT frames measured using the same input parameters is always 1. It is only when two signals are averaged over some period of time that nonlinear issues appear so the Coherence feature is disabled when the number of averages is set to 1. Overall coherence tends to decrease as the number of averages increases. Additional factors that can adversely affect the coherence of transfer function data include delay between the two signals, insufficient energy in the reference signal at a given frequency, acoustical influences (i.e., reflections and reverberation), and ambient or electrical noise. Nonlinear processors such as compressors and limiters in the measurement signal path can also have a negative influence on coherence and should therefore be bypassed for Frequency Response and Impulse Response measurements. 2.1.11 Signal Alignment When performing Frequency Response measurements, it is essential that the measurement and reference input signals be aligned in time. To make a meaningful comparison of two signals, the transfer function calculation must measure the same piece of each signal at the same time. With most analog audio equipment, this is not an issue and compensation is not normally required. However, all digital signal processors have some propagation delay, as does sound travelling through air to a microphone. Before a meaningful Frequency Response measurement of a DUT/SUT with propagation delay can be made, the delay must be found and compensated for. This process requires finding the delay in the measurement signal and adding it to the reference signal. Smaart 6's Delay Locator and Internal Delay functions make this process easy (see page 52). 30 EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography 2.2 Glossary of Terms Analog to Digital (A/D) Conversion: The process of sampling the amplitude of an analog signal at regular intervals to create a digital representation of the signal. Amplitude: The size of a real number (e.g., a number of Volts), in either the positive or negative direction. The term amplitude typically refers to numbers that are not complex or plotted on a logarithmic scale, such as the numbers stored in the A/D process. (Numbers expressed logarithmically are more properly called magnitudes.) Attenuation: A decrease in the level of a signal. Attenuation can refer to reduction in level for a specified frequency range or a decrease in the overall level. Coherence: A mathematical function that represents the linearity between two signals. Coherence is conventionally expressed as a value between 0 and 1. Note that coherence is affected by measurement conditions and the number of averages used. Compressors: Electronic devices that cause changes in gain (typically attenuation) as a function of the input level. These devices should NOT be used when making Frequency Response measurements as they are nonlinear by nature. Crosstalk: Undesired energy in one signal (or channel) introduced from an adjacent signal or channel. Data Window: A mathematical function used to reduce the negative effects of truncation that occurs when a finite number of FFT points are used to transform time domain data into the frequency domain. The Data Window(s) work by reducing the amplitude of the time domain data at the beginning and end of the FFT data series. Decay Rate: The rate at which a signal decays (diminishes in magnitude), usually a function of frequency and expressed in either decibels per second, or relative to the amount of time that would be required for the signal to decay 60 decibels at the given rate of decay. (see Reverberation Time) Decibel: The decibel, often abbreviated as dB, is a logarithmic ratio between two values. In acoustics, decibels most commonly refer to the ratio of an input level to the output level of a system, or a given level compared to a fixed reference. Dynamic Range: The difference in level between the highest and lowest signal a system can accept or reproduce. FFT: The Fast Fourier Transform is a mathematical technique used to transform time domain data into the frequency domain. The term "Fast" refers to the fact that when the number of time domain samples is a power of 2 (16, 32, 64, 128, 256...) the calculations can be performed very quickly by a digital computer. 31 EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography FFT Time Constant: The amount of time it takes to collect all the samples required for a single FFT frame of a given size at a given sampling rate. The time constant of an FFT, also called the time window, can be calculated by dividing the FFT size by the sampling rate. For example, a 4k FFT sampled at 44.1k samples/second has a time window of 0.09 seconds. Graphic Equalizer: A device with a number of filters used to change the gain or attenuation of a signal at pre-selected frequencies. The bandwidths of the filters are typically set to one- or 1/3-octave and are usually not adjustable by the end user. Latency: The delay through a given unit or system. Latency is often referred to as the throughput delay of a device. It is typical for digital delays to have a small latency even when they are set to zero time delay. Linear Scale: The term linear, refers to a set of values or scale of a graph on which values are evenly spaced. On a linear scale, each value (or unit) has equal dimension. Logarithmic Scale: A scale where each power of a given number (e.g., ten) is given equal dimension. Magnitude: A number assigned to a quantity so that it may be compared with other quantities. For complex quantities, the magnitude is the square root of the sum of the squares of the real and imaginary parts. Nyquist Frequency: In digital audio, the Nyquist frequency is equal to one half of the sampling rate. The Nyquist frequency represents the highest frequency obtainable in digitized a signal sampled at a given sampling rate. Octave-Band Resolution: Octave band resolution combines all data points in a given octave and displays a total energy value for each octave band (as opposed to a linear or logarithmic narrowband display that plots the value of individual FFT data points). Standard octaves used in audio measurement are centered on 16, 31.5, 63, 125, 250, 500, 1 kHz, 2 kHz, 4 kHz, 8 kHz. and 16 kHz (cycles per second). Overlap: For the purposes of Smaart 6, overlap refers to the amount of data each successive FFT Frame shares in common with the one before. Overlapping FFT frames are analogous to shingles on a roof. When no overlap is used, each new FFT frame begins where the last one stopped, as beads on a string. Parametric Equalizer: Equalizers are devices with one or more filters that affect the frequency content of a signal. On a parametric equalizers, the parameters of the filter(s) including gain or attenuation, frequency and bandwidth are user-adjustable. Phase Shift: A timing difference in a signal (relative to some reference) at one or more frequencies, typically expressed in degrees. Pink Noise: A random (or pseudorandom) signal in which, over a given averaging period, each Octave-band has an equal amount of energy. 32 EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography Propagation Delay: The time it takes for sound to travel from one place (typically a loudspeaker) to another place (typically a microphone). Reverberation Time: The amount of time required for audio energy introduced into a system (typically a room) to diminish, or decay a specified number of decibels. Often expressed as an RT60 value. RT60: Reverberation time. The amount of time required for a system, typically a room, to decay 60 decibels. (see Decay Rate) Sampling Rate (SR): The number of data points measured per second used in the analog to digital conversion process expressed in Hz. Signal to Noise Ratio (S/N): The ratio of signal to noise level in a measurement. If the S/N is too low, the noise overwhelms the measurement and renders it invalid. Spectrograph: A three-dimensional plot, displayed in two dimensions with color representing the third dimension (or z-axis). The spectrograph is a topographical representation of the common waterfall display. Spectrum: The frequency content of a given signal. Speed of Sound: The speed of sound is dependent on the material of propagation, the temperature and several other factors. Typical values for the speed of sound in air are 1120 ft/s, or 341.376 m/s. This is the value Smaart 6 uses to calculate distance equivalents for time differences. System Under Test (SUT): The system being tested by Smaart 6. This could be a single device or an electroacoustic system such as speakers/amplifiers. Time Window: The time constant (or effective time constant) of a measurement or other process. Time Constant (TC): TC = FFT size/SR White Noise: A random (or pseudorandom) signal in which over a given averaging period, each frequency has equal energy. 33 EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography 2.3 Selected Bibliography The following is a list of publications suggested for readers who want to expand their understanding of the physical and theoretical concepts and mathematical procedures underlying Smaart 6, sound system design, and acoustics. Badmaieff, A. & Davis, D. How to Build Speaker Enclosures. Indianapolis: Howard W. Sams & Co., 1966. Ballou, G. ed. Handbook for Sound Engineers - The New Audio Cyclopedia. Indianapolis: Howard W. Sams & Co., 1987. Bensen, K. B. ed. Audio Engineering Handbook. New York: McGraw-Hill Book Co., 1988. Beranek, L. L. Acoustical Measurements. New York: John Wiley and Sons, Inc., 1949; reissued by the American Institute of Physics for the Acoustical Society of America, New York:1986. Beranek, L. L. Acoustics. New York: McGraw-Hill book Co., 1954; reissued by the American Institute of Physics for the Acoustical Society of America, New York, 1986. Brigham, E. The Fast Fourier Transform and its Applications. Englewood Cliffs: PrenticeHall, Inc., 1988 Davis, D. & Davis, C. Sound System Engineering, Second Edition. Indianapolis: Howard W. Sams & Co., 1987. Davis, G. & Jones, R. Yamaha Sound Reinforcement Handbook, Second Edition. Milwaukee: Hal Leonard, 1989. Digital Signal Processing Committee, ed. Selected Papers in Digital Signal Processing, II. IEEE Press Selected Reprint Series, New York: IEEE Press, 1975. Digital Signal Processing Committee, ed. Programs for Digital Signal Processing. IEEE Press Selected Reprint Series, New York: IEEE Press, 1979. Eargle J. Handbook of Sound System Design. Plainview: Elar, 1989 ______. The Microphone Handbook. Plainview: Elar, 1982 Egan, M. D. Architechtural Acoustics. New York: McGraw-Hill Book Co., 1988. Everest, F. A. Successful Sound System operation. Blue Ridge Summit: TAB Books, 1985. ______. The Master Handbook of Acoustics. Blue Ridge Summit: TAB Books, 1983. Giddings, P., Audio System Design and Installation. Indianapolis: Howard W. Sams & Co., 1990. Harris, H. J. "On the Use of Windows for Harmonic Analysis with the discrete Fourier Transform," Proceedings of the IEEE, Vol. 66, No. 1, pp. 51-83, January 1978. Huber, D.M., Microphone Manual: Design and Application. Indianapolis: Howard W. Sams & Co., 1988. Ifeachor, E. C. & Jervis, B. W. Digital Signal Processing: A Practical Approach, Second Edition, Essex, England: Prentice Hall, 2002 34 EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography Knudson, V. O. & Harris, C. M. Acoustical Designing in Architecture, New York: John Wiley and Sons, Inc., 1950; reissued by the American Institute of Physics for the Acoustical Society of America, New York, 1978. Lubman D. and Wetherill E., eds. Acoustics of Worship Spaces. New York: The American Institute of Physics, 1983 McCarthy, B. Meyer Sound Design Reference For Sound Reinforcement. Berkely: Meyer Sound Laboratories, 1998 Olson, H. F. Acoustical Engineering. Princeton: Van Nostrand, 1957; reissued by Professional Audio Journals, Philadelphia, 1991. Olson, H. F. Music, Physics and Engineering. New York: Dover Publications, 1967. Oppenheim, A. V., ed. Applications of Digital Signal Processing. Englewood Cliffs: PrenticeHall, Inc., 1978. Oppenheim A. V. & Schafer, R. Digital Signal Processing. Englewood Cliffs: Prentice-Hall, Inc., 1975. Oppenheim, A. V., Willsky, A. S. & Young, I. T., Signals and Systems. Englewood Cliffs: Prentice-Hall, Inc., 1983. Otnes, R. K. & Enochson, L. Applied Time Series Analysis. New York: John Wiley and Sons, Inc.,1978 Rabiner, L. R. & Rader, C. M., ed. Digital Signal Processing. IEEE Press Selected Reprint Series, New York: IEEE Press, 1972. Rona, J. MIDI: The Ins, Outs, and Thrus. Milwaukee: Hal Leonard, 1987. Strutt, J. W. (Lord Rayleigh, 1877). Theory of Sound. New York: Dover Publications, 1945. Tremaine, H. Audio Cyclopedia, Second Edition. Indianapolis: Howard W. Sams & Co., 1969. 35 EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography 36 EAW Smaart 6 Operation Manual Analysis Modes and Display Types Chapter 3: Analysis Modes and Display Types Smaart 6 has two analysis modes: Real-time and Impulse Response (IR Analysis). These run in separate windows. Real-time mode processes incoming data continuously and offers four display types: RTA, Spectrograph, Magnitude, and Phase. RTA and Spectrograph displays are considered Spectrum measurements, where each data set displayed is based directly upon FFT data from a single signal. The Magnitude and Phase displays show Frequency Response data based on the transfer function of two signals. Smaart 6 starts up with a single-pane view with the RTA display type. The Spectrum and Freq. Resp. buttons configure the real-time window with the two displays corresponding to each of their respective measurement types: · · Click the Spectrum button to display a two-pane window with display types set to Spectrograph (top) and RTA (bottom). Click the Freq. Resp. button to display a two-pane window with display types set to Phase (top) and Magnitude (bottom). Even if the single-pane View is selected, clicking the Spectrum or Freq. Resp. buttons changes to a two-pane View. Of course, any display type can be subsequently selected. Figure 3-1 View and plot display after clicking the Spectrum button 37 EAW Smaart 6 Operation Manual Analysis Modes and Display Types Click the IR Analysis button to open the Impulse Response window. Impulse Response mode collects and stores a limited amount of data and then offers two display types: Time and Frequency. Clicking the IR Analysis button does not override the selected View. Figure 3-2 Impulse Response Window 3.1 Spectrum Measurements Real-time spectral analysis is an excellent tool for feedback hunting, ear training, and monitoring a program material's frequency content. RTAs are also still commonly used to equalize cinema systems but dual-port FFT analyzers, like Smaart, have gradually replaced RTAs as the tool of choice for tuning most larger sound systems, particularly sound reinforcement systems. A dual-FFT analyzer can measure all three dimensions of sound (frequency, energy, and time) whereas an RTA cannot reveal the critical factors of timing and phase. A good RTA is still a very useful tool and Smaart 6 provides a powerful, flexible implementation for real-time spectral analysis. 3.1.1 RTA The RTA displays the amount of energy present in various frequency ranges across the audible spectrum, typically in fractional octave bands. The RTA display functions as a dual-channel, FFT-based real-time spectrum analyzer. This display plots the spectrum (magnitude on the y-axis vs. frequency on the x-axis) of the signals arriving on the selected reference and measurement inputs. The colors of the two live data sets on the RTA display correspond to those used in the input level meters. 38 EAW Smaart 6 Operation Manual Analysis Modes and Display Types Press the Start button in the real-time window to begin all real-time measurement operations. When the RTA display is active, time-domain audio data from the A/D converter of your sound hardware is continuously transformed into the frequency domain using a Fast Fourier Transform (FFT). The FFT data can be plotted on the RTA display in real time, either in raw narrowband form or processed into octave or fractional-octave bands. The magnitude for each frequency band (or data point) on each of the two input channels is updated several times per second, depending on the speed of your computer, FFT size, and sampling rate. The (y-axis) magnitude range of the RTA plot can be changed using the RTA dB Range Max and Min fields in the Spectrum tab of the Options dialog. The magnitude range can be further restricted by dragging a rectangular region within the plot. There also hot keys for plot ranging (see Keyboard Shortcuts on page 103). Click on the numbers for either axis to return the scale to normal (determined by RTA dB Range values). Using the default Full Scale display calibration, the maximum magnitude value of 0 dB is equal to the maximum A/D amplitude value obtainable at the current sampling resolution (i.e., 16/24 bits per sample). That means that a sine wave input signal with amplitude exactly equal to the maximum input voltage of your sound hardware's A/D converter should yield 0 dB at the sine wave's frequency on the RTA plot. Full Scale calibration is adequate for applications concerned only with the relative differences between frequencies. Smaart 6 also includes a calibration function that allows moving the decibel range of the raw incoming data up or down to correlate to Sound Pressure Level (SPL) or another external reference. The RTA's frequency scale may be displayed in octave, 1/3-, 1/6-, 1/12-, or 1/24-octave resolution. Set the frequency scale for the Spectrum displays from the Scale control under the Spectrum button. The frequency range of the Spectrum and Magnitude plots may be set using hot keys (page 103) or by recalling one of the four Frequency Zooms (set in Options->Zoom) assigned to the 1-4 keyboard keys. The x- and y-axis ranges of most Smaart charts can be set by clicking and dragging to draw a rectangle around the desired plot area, then releasing the mouse button. Click the frequency numbers to return the scale to normal. 39 EAW Smaart 6 Operation Manual Analysis Modes and Display Types 3.1.2 Spectrograph The Smaart 6 Spectrograph is a second type of RTA display that shows an input signal's frequency content over some period of time. Instead of showing just one FFT measurement at a time (whether averaged or instantaneous) like the RTA display, the live Spectrograph displays a record of the most recent 100 or more RTA updates. Figure 3-3 Spectrograph display The Spectrograph display is a variation of a real-time spectrum analyzer (RTA). A standard RTA indicates magnitude values for each fractional octave frequency band by vertical bars of varying height; a new bar graph replaces the previous one each time the display is updated. The Spectrograph plots each RTA data update as a horizontal stripe, with signal strength at each frequency represented by different colors. Stacking a number of these slices one above the next displays the input signal's spectral changes over time. The Spectrograph display shows three dimensions of data: · · · time: on the x-axis frequency: on the y-axis magnitude: represented by color The colors mapped to magnitude values are determined by the Spectrograph dB Range Max and Min fields in the Spectrum tab of the Options dialog. Out of range values above the current magnitude range specified for the Spectrograph are indicated on the plot in white. Magnitude values below the current magnitude range are indicated in black. 40 EAW Smaart 6 Operation Manual Analysis Modes and Display Types Figure 3-4 Spectrograph dB Range The frequency scale of the Spectrograph is set by clicking and dragging a rectangular area, which becomes the new displayed range. Click on the frequency axis numbers to return the scale to normal. 3.1.3 Spectrum Measurement Parameters Frequency Scale The RTA's frequency scale may be displayed in octave, 1/3-, 1/6-, 1/12-, or 1/24-octave resolution or as a narrowband display of the underlying FFT data with linear or logarithmic (Lin/Log) scaling. Set the frequency scale for the Spectrum displays from the Scale control under the Spectrum button. Figure 3-5 Frequency Scale list The frequency range of the Spectrum and Magnitude plots may be set using hot keys (page 103) or by recalling one of the four Frequency Zooms (set in Options->Zoom) assigned to the 1-4 keyboard keys. The x- and y-axis range can be set by clicking and dragging to draw a rectangle around the desired plot area, then releasing the mouse button. Click the frequency numbers to return the scale to normal. 41 EAW Smaart 6 Operation Manual Analysis Modes and Display Types Averaging Averaging is used in RTA, Spectrograph, and Frequency Response measurements to increase the effective signal-to-noise ratio (S/N) of the measurement and reduce the influence of transient events. This stabilizes the display and makes overall trends easier to see. Spectrum measurements use RMS averaging but several integration schemes are available: linear first in, first out (FIFO), Infinite, Fast, Slow, and Exponential. FIFO averaging is a simple arithmetic average of the 2n (n = 0, 1, 2...7) most recent FFT frames with equal weight given to each. Note that when the number of averages is set to 1, averaging is not performed; each display update includes only the magnitude data from the most recent FFT frame. Infinite (Inf) averaging is similar to FIFO in that every FFT measurement in the average is given equal weight but rather than looking at a fixed number of the most recent FFT frames, this option keeps a running of average of all FFTs recorded since the last time the buffer was flushed. Averaging buffers are flushed (re-seeded) when changes are made to averaging parameters, FFT size, or sampling rate, starting the analyzer, switching between display types, and pressing the V key. Figure 3-6 Average options (left); Weight options (right) Weighting Curves The Weight setting in the Spectrum display control section applies a frequency-dependent weighting curve to the RTA, Spectrograph displays. Some common weighting curve types are shipped with the program (right of Figure 3-6), including ANSI/IEC A and C types and X curves for cinema systems. Additional curves may be added to this list by adding files to the Weighting folder. The Spectrum section's Weight control applies only to the RTA and Spectrograph displays. Spectrum and Freq. Response (Magnitude only) displays can be weighted independently. See Weighting Curves on page 65. 42 EAW Smaart 6 Operation Manual Analysis Modes and Display Types