Sound Boards

41 SOUND BOARDS

CONT CO NTEN ENTS TS AT A GL GLAN ANCE CE Understanding Sound Boards The recording process The playback process The concept of “sampling” Data bits vs. sound quality The role of MIDI Inside a sound board

Knowing the Benchmarks Decibels Frequency response Signal-to-noise ratio Total harmonic distortion Intermodulation distortion Sensitivity Gain

Using Microphones Microphone types Phantom power Choosing a microphone

Troubleshooting a Sound Board Drivers and driver order Full-duplex drivers .WAV playback problems under Windows 95 Symptoms

Further Study

largely overlooked in early systems. systems. Aside from Sound is an area of the PC that has been largely a simple, oscillator-driven oscillator-driven speaker, the early early PCs were mute. Driven largely by the demand for better PC games, designers developed stand-alone sound boards that could read sound data recorded in separate files, then reconstruct those files into basic sound, music, 1192

UNDERSTAND UNDER STANDING ING SOUND BOARD BOARDS S

FIGURE FIG URE 4141-1 1

A Logitech SoundMan Wave sound board.

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Copyright

© 1995 Logitech Logitech Corporation Corporation

and speech. Since the beginning of the decade, decade, those early sound boards have blossomed blossomed into an array of powerful, high-fidelity sound products, capable of duplicating voice, orchestral soundtracks, and real-life real-life sounds with uncanny realism (Fig. (Fig. 41-1). Not only have sound products helped the game industry to mature, but they have been instrumental in the development of multimedia technology (the integration of sound and picture), as well as Internet Web phones and other communication communication tools. This chapter is intended to explain the essential ideas and operations of a contemporary sound board, and show you how to isolate a defective sound board when problems arise.

Understanding Sound Boards Before you attempt to troubleshoot a problem with a sound board, you should have an understanding of how the board works works and what it must accomplish. accomplish. This type of background helps you when recommending a sound board to a customer or choosing a compatible card as a replacement. replacement. If you already have have a strong background in digital sound concepts and software, feel free to skip directly to the troubleshooting portion of this chapter.

THE RECORDING PROCESS All sound starts as pressure as pressure variations traveling through the the air. Sound can come from from almost anywhere—a barking dog, a laughing child, a fire engine’s siren, a person speaking. You get the idea. The process of recording sound to a hard drive requires sound to be carried through several manipulations (Fig. 41-2). First, sound must be translated from pressure variations in the air to analog electrical signals. This is accomplished by a microphone. These analog signals are amplified by the sound card, then digitized (converted (converted to a series of representative digital digital words each taken at a fixed time interval). The resulting stream of data is processed and organized through the use of software, which places the

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S Y S T E M D A T A A N D T R O U B L E S H O O T I N G

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Sound board hardware Sound Mic

Analog signal

Digital signal

Software driver

Storage device (hard drive)

FIGURE FIGURE 41-2 41-2

The sound-board recording process. Sound board hardware L spkr.

Software driver Digital signal

Analog signal R spkr.

Storage device (hard drive)

FIGUR FIGURE E 41-3 41-3

The sound-board playback process.

data (as well as any overhead or housekeeping data) into a standard file format. The file is saved to the drive of choice (typically, a hard drive).

THE PLAYBACK PROCESS Simply speaking, the playback process process is virtually the reverse of recording recording (Fig. 41-3). A software application opens a sound file on the hard drive, then passes the digital data back to the sound card. Data is translated back into into equivalent analog levels—ideally, levels—ideally, the reconstructed shape of the analog signal closely closely mimics the original digitized digitized signal. The analog signal is amplified, then passed passed to a speaker. If the sound was recorded in stereo, the data is divided into two channels that are separately converted back to analog signals, amplified, and sent to their corresponding speakers. speakers. Speakers convert the the analog signal back into traveling pressure waves that you can hear.

THE CONCEPT OF “SAMPLING” To appreciate the intricacies of a sound card’s operation, you must understand the concept of digitization of digitization (otherwise known as sampling as sampling ). ). In principle, sampling is a very straightstraightforward concept; an analog signal is measured periodically, and its voltage at each point in

UNDERSTAND UNDERSTANDING ING SOUND BOARDS BOARDS

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time is converted to a digital number. number. The device that performs this conversion conversion is known as an Analog-to-Digit an Analog-to-Digital al Converter (ADC) . It sounds simple enough in principle, principle, but it has some important wrinkles. The problem with sampling is that a digitizer circuit has to capture enough points of an analog waveform to reproduce it faithfully. The example in Fig. 41-4 illustrates the importance of sampling rate. Waveforms A and B represent the same original signal. Waveform A is sampled at a relatively slow rate—only a few samples are taken. The problem comes when the signal is reconstructed with a a Digital-to-Analog Converter (DAC). (DAC). As you see, there are not enough sample points to reconstruct the original signal. As a result, some of the information in the original signal is lost. This form of distortion is known as aliasing . Waveform B is the same signal, but it is sampled at a much higher rate. When that data is reconstructed, the resulting signal is a much more faithful reproduction of the original. As a rule, a signal should be sampled at least twice as fast as the highest frequency contained in the signal—this is known as Nyquist’s as Nyquist’s Sampling Theorem. Theorem . The lowest lowest standard sampling rate used with today’s sound boards is 11kHz—this allows fair reproduction of normal speech and vocalization vocalization (up to about 5.5kHz). 5.5kHz). However, most low-end sound boards can digitize signals signals up to 22kHz. Unfortunately, the human range of hearing is about 22kHz. To capture sounds reasonably reasonably well throughout the entire entire range of hearing, you would need a sampling rate of 44kHz—often known as CD-quality sampling because because it is the same rate used to record record audio on CDs. The disadvantage to high sampling sampling rates is disk space (and sound file file size). Each sample is a piece of data, so the more samples samples taken each second, the larger and faster a file grows.

DAT DATA BITS VS . SOUND Q UALITY Not only does the number of samples affect sound quality, but also the precision (or num ber of bits) of each sample. sample. Suppose that each sample is converted converted to a 4-bit number. That means each point can be represented by a number from 0 to 15—not much precision there.

Wavef avefor orm m A: orig origin inal al

Wavef avefo orm B: orig origin inal al

Wavefor aveform m A: recons reconstru tructe cted d

Wavefor aveform m B: recons reconstru tructe cted d


The concept of sampling rate .

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If 8 bits are used for each sample, 256 discrete levels can be supported. supported. But the most popular configuration is 16-bit conversion, which allows a sample to be represented by one of 65,536 levels. At that level of resolution, resolution, samples form a very close replica replica of the original signal. Many of today’s sound boards are 16-bit. 16-bit.

THE ROLE OF MIDI Although the majority of a sound card is geared toward handling the recording and play back of sound files, the Musical the Musical Instrument Digital Interface (MIDI) port has become an inexpensive and popular addition addition to many sound-card designs. designs. The MIDI standard is dedefined by hardware, software, and electrical electrical interconnections. At the core of a MIDI interface is a synthesizer synthesizer IC. Unlike a sound file, which basically contains contains the digital equivalent of an analog waveform, a MIDI file is a set of instructions for playing musical notes. Each note is sent to the synthesizer, synthesizer, along with duration, pitch, pitch, and timing specifications. The synthesizer can be made to replicate replicate a variety of musical instruments, instruments, such as a piano, guitar, harmonica, flute—you flute—you name it. The high-end sound boards are capable of synthesizing a small orchestra. orchestra. Because most synthesizers synthesizers can process several channels simultaneously, the MIDI standard supports playing a number of “instruments” (or voices) at the same time. Thus, very high-quality high-quality music can be produced produced with MIDI on a PC. The two most common synthesizer types are FM and Wavetable. Figure 41-5 illustrates the kinds kinds of things that MIDI is capable of. Pre-recorded MIDI files can be read from a storage device, such as a hard-drive file, or from CD-ROM (many games include an orchestral-quality orchestral-quality MIDI MIDI soundtrack on the CD). CD). The MIDI data is passed through to the sound board’s synthesizer which reproduces the sound, and out to the amplified speakers. If you plan to compose music yourself, yourself, you can interface a MIDI instrument to the sound board’s board’s MIDI port. Using MIDI sequencer sequencer software, the notes played on the instrument will be heard through the speaker, as well as recorded to the MIDI file on the hard drive. Notice that you do not need a MIDI instrument to playback a MIDI file, but you need an instrument and sequencer software to create a MIDI file. Also, Sound board hardware

Hard drive

MIDI port

Synthesizer

Speakers

Sequencer software MIDI instrument


The path of MIDI signals through the PC.

UNDERSTAND UNDERSTANDING ING SOUND BOARDS BOARDS

ADC

Audio amp

1197

Mic. in Line in

Synthesizer RAM

CD audio

Digital signal processor (DSP)

Mixer/ filter

Audio amp

ROM

Speaker out Line out

MIDI/ joystick interface

Bus interface circuits

MIDI instrum. or joystick

PC bus

FIGU FIGURE RE 41-6 41-6

Simplified block diagram of a sound board.

because MIDI is not sound (but rather sound “blueprints”), the same MIDI composition entered on a keyboard can be played back as a harp, or a guitar, or a flute.

INSIDE A SOUND BOARD Now that you are aware of the major functions a sound board must perform, you can see those functions in the context of a complete board. Figure 41-6 shows a simplified block diagram of a sound board. It is important that your own own particular sound board might differ somewhat, but all contemporary boards should contain these subsections. The core element of a sound board is the Digital the Digital Signal Processor (DSP). (DSP) . A DSP is a variation of a microprocessor that is specially designed to manipulate large volumes of digital data. Like all processor processor components, the DSP DSP requires memory. memory. A ROM contains all of the instructions needed to operate the DSP and direct the board’s major operations. A small quantity of RAM serves two purposes: it provides a “scratch pad” area for the DSP’s calculations and it serves as a buffer for data traveling to or from the PC bus. Signals entering the sound board are passed through an amplifier stage and provided to an A/D converter. When recording occurs, the DSP DSP runs the A/D converter and accepts accepts the resulting conversions for for processing and storage. Signals delivered by a microphone are typically quite faint, so they are amplified amplified significantly. Signals delivered to the “line” input are often much stronger (such as the output from a CD player or stereo preamp), so it receives less amplification. For signals leaving the sound board, the first (and often most important) stop is the mixer. mixer. The mixer combines CD-audio, CD-audio, DSP sound output, and synthesizer synthesizer output into a single analog channel. channel. Because most sound boards boards now operate in a stereo stereo mode, most have two mixer channels and and amplifier stages. The audio amplifier stage(s) stage(s) boost the

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analogs signal for delivery to stereo speakers. If the sound will be driving a stereo system, a “line” output provides a separate output. Amplifier output can be adjusted adjusted by a single master volume control located on the rear of the board. Finally, a MIDI controller is provided to accommodate the interface of a MIDI instrument to the sound board. In many cases, the interface interface can be jumpered to switch the concontroller to serve as a joystick port. That way, the sound board can support a single joystick joystick if the MIDI instrument will will not be used. MIDI information information processed by the DSP will be output to the on-board synthesizer.

Knowing Knowing the Benchmarks Ben chmarks An important aspect of sound boards boards is their audio benchmarks. Unlike logic and processing circuitry, which is measured in terms of millions of operations per second, the benchmarks that define a sound card are very much analog. If you are an audiophile, many of the following terms might already be familiar. If most of your experience has been with logic systems, however, these concepts will appear very different than many of the other sections in this book.

DECIBELS No discussion of sound concepts is complete without an understanding of the decibel (dB). (dB). Decibels are used because they are logarithmic. logarithmic. Human hearing is not a linear response. response. If you increase the power of your stereo output from 4 W to 16 W, the sound is not 4 times louder—it is only twice twice as loud. If you increase the power from 4 W to 64 W, the sound sound is only three times times as loud. In human terms, amplitude perception is measured logarithmically. As a result, very small decibel decibel values actually relate relate to substantial amounts of power. The accepted formula formula for decibels decibels is:

gain (in dB) = 10 log10

Pout

 P in

Don’t worry if this formula looks intimidating. intimidating. Chances are that you will not need to use it, but consider what happens when output power power is greater than input power. Suppose that a 1-mW signal is applied to a circuit and a 2-mW signal leaves. The circuit provides a gain of +3 dB. Suppose that the situation situation was reversed, where a 2-mW signal signal is applied to the circuit and a 1-mW signal signal leaves it. The circuit would then then have a gain of -3 dB. Negative gain is a loss, also called attenuation. attenuation. As you see, a small dB number number represents a large change in signal levels.

FREQUENCY RESPONSE Expressed simply, the frequency response of a sound board is the range of frequencies that the board will handle uniformly. Examine the sample sample graph of Fig. Fig. 41-7. Ideally, a sound board should be able to produce the same amount of power (0 dB) across the entire work-

KNOWING THE BENCHMARKS

dB 6

1199

Ideal response

4

Satisfactory response

2

kHz

0 2

Poor response

4 6

0.01


0.1

1.0

10.0

100.0

A sample sound board frequency-response curve.

ing frequency range (usually 20Hz to 20kHz). 20kHz). This would show up as a flat line across the graph. In actuality, however, however, this is not practical; invariably a rolloff of signal signal strength will be at both ends of the operating range. A good-quality sound board will demonstrate sharp, steep rolloffs. rolloffs. As the rolloffs get longer and more shallow shallow at high and low frequencies, the board has difficulty difficulty producing sound power at those those frequencies. The result is that bass and treble ranges might sound weak, which affects the sound’s overall fidelity. By looking at a frequency-response curve, you can anticipate the frequency ranges where a sound board might sound weak.

SIGNAL-TO-NOISE RATIO RATIO The signal-to-noise The signal-to-noise ratio (SNR) of a sound board is basically the ratio of maximum undistorted signal power to the accompanying electronic noise being generated by the board (primarily hum and hiss), expressed expressed in decibels. Ideally, this will be a very large dB num ber, which would indicate that the output signal is so much stronger than the noise signal that for all intents and purposes purposes the noise is imperceptible. imperceptible. In actuality, a good-quality good-quality sound board will enjoy an SNR of 85 dB or higher—but higher—but these are difficult to find. For most current sound boards with SNR levels below 75 dB, hum and hiss are audible during silent periods, as well as a certain amount of sound “grit” underlying sound and music re production. Some very inexpensive inexpensive sound boards are on the market with with SNR levels as low as 41 dB (noise might be noticeable and actually annoying). You might also find the SNR value expressed as an “A-weighted” decibel number. The reason for this is that human hearing is not equal at all frequencies, so we cannot hear all noise equally. The process of “A-weighting” “A-weighting” emphasizes the noise levels at frequencies frequencies that we are most sensitive to. Resulting SNR values are often several several dB higher (better) than non-weighted SNR values. values. Be careful here; a sound board with a low SNR might use the A-weighted value in the specification specification sheet. If this is the case, subtract about 3 or 4 dB for the actual SNR figure.

TOTAL HARMONIC DISTORTION Sound and music are rich in harmonics (overtones) that are basically integer multiples of an original frequency signal (although (although at much lower levels). As a consequence, harmonics

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are a valuable attribute of sound. The number and amplitude of harmonics provide the sound characteristics that allow you to distinguish between a guitar, flute, piano, or any other musical instrument played at the same note—without harmonics, every instrument would just produce flat tones, and every instrument would sound exactly the same. However, when sound is produced in an electronic circuit, other unwanted harmonics are generated that can alter the sound of the music being produced (thus the term harmonic distortion). distortion). The total harmonic distortion (THD) of a sound board is the root-mean squared (RMS) sum of all unwanted harmonic frequencies produced, expressed as a percentage of the total undistorted undistorted output signal level. In many cases, the RMS value of noise is added to THD (expressed as THD+N ). ). The lower this percentage percentage is, the better. better. THD+N values over 0.1% can often be heard, and suggest a less-than-adequate sound-board design.

INTERMODULATION DISTORTION This figure is related to harmonics. harmonics. When two or more tones are generated generated together, am plifiers create harmonics, as well as tone combinations. combinations. For example, if a 1kHz and 60Hz tone are mixed together, intermodulation harmonics will be generated (e.g., 940Hz, 880Hz, 1060Hz, 1120Hz, 1120Hz, etc.). This intermodulation intermodulation gives sound sound a harsh overtone. overtone. Because intermodulation is not related to sound quality, it is a form of distortion that should be kept to a very low level. level. Like THD, Intermodulation THD, Intermodulation Distortion (IMD) is the RMS sum of all unwanted harmonic frequencies expressed as a percentage of the total undistorted output signal level. IMD should be under 0.1% on a well-designed well-designed board.

SENSITIVITY Although it does not directly affect the fidelity of sound reproduction, sensitivity can be an important specification. Sensitivity is basically the amplitude of an input signal (such as a microphone signal) that will produce the maximum undistorted signal at the output(s) with volume at maximum.

GAIN By itself, sensitivity is hard to apply to a sound board, but if you consider the board’s out put power versus its input signal power and express the ratio as a decibel, you would have the gain of the sound board. board. Many sound boards offer offer a potential gain of up to 6dB. However, it is important that not all sound boards provide positive gain—some boards actually attenuate the signal even even with the volume at maximum. maximum. In practical terms, terms, this usually forces you to keep the volume control at maximum.

Using Microphones An ever-growing number of sound card owners are using their sound cards to record sound or broadcast sound over the Internet through through such applications as WebPhone. Sound recording demands the use of microphones, and not all microphones work properly with every sound board. Often, the user mistakes mistakes a poor microphone response response as being a prob-

USING MICROPHONE MICROPHONES S

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lem with the sound card. This part of the chapter looks at some important considerations considerations for choosing and using a microphone.

MICROPHONE MICROPHONE TYPES The three types of microphones are: dynamic, dynamic, condenser, and electret condenser. All three microphone types are available for sound boards: Dynamic Dynamic microphones are typically typically hand-held or desktop units. units. They have a larger response range range and usually sound better than condenser microphones. A dynamic microphone does not require phantom power because the diaphragm element in the microphone can create enough electric current for the sound board to use. s Condenser Condenser microphones are the small multimedia microphones that are typically sold with computers. computers. When you open a new sound board and take the micro phone out of the box, it is almost always a condenser condenser microphone. They do not have as good a response range as dynamic microphones, and they also have a smaller diaphragm—this demands phantom power from the sound board. s Electret condenser Electret condenser microphones are basically condenser micro phones with a built-in battery for power. They have the same response as a condenser microphone, but they do not require phantom phantom power to operate. Some electret condenser microphones will allow allow you to remove this internal battery. battery. With the battery not installed, phantom power would be required. s

PHANTOM POWER The next question is “What is phantom power?” Phantom power is simply a small, lowcurrent power supply on the sound board, which is used to power some microphones. Such devices as dynamic microphones can produce enough current on their own to avoid the use of phantom power, but condenser microphones microph ones demand phantom power as a current source. Here’s the main problem with today’s sound boards—not all of them provide switchable phantom power. Ideally, sound boards (such as the Ensoniq Soundscape) would provide phantom power and allow you to jumper the phantom power on or off, depending on which microphone you plan to use. If you use a dynamic microphone, you’d switch phantom power off. If you use a condenser microphone, microphone, you’d you’d switch phantom phantom power on. If a sound board does not provide phantom power at all, you’re stuck using a dynamic microphone or a powered electret condenser microphone. If a sound board provides full-time phantom power (and you cannot turn it off), you’ll need to stay with a condenser microphone. You can probably see the potential for trouble trouble here. If you use a condenser microphone on an unpowered sound board, the microphone will not work at all (or generate little more than faint noise). On the other hand, plugging plugging a dynamic or electret electret microphone into into a powered sound board will usually result in severe clipping—once again, you’ll capture little more than noise.

CHOOSING A MICROPHONE Whether you’re choosing a microphone for yourself or recommending one to someone else, remember some considerations. considerations. Perhaps the most important issue is the application.

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If you just need a basic, inexpensive microphone to record a few simple voice notes, a condenser or electret microphone would work just fine and your sound board will require a phantom power supply. If you want to record more professional professional vocals or if you are preparing a presentation, a dynamic microphone will generally provide the best results (and no phantom power is needed).

Troubleshooting Troubleshooting a Sound Board Traditionally, sound boards use many of the same chipsets and basic components, but because each board is designed a bit differently, it is very difficult for commercial diagnostic products to identify failed IC functions. functions. For the most part, commercial and shareware shareware diagnostics can only identify identify whether a brand-compatible brand-compatible board is responding or not. As a result, this chapter chapter will take the sub-assembly sub-assembly replacement replacement approach. When a sound board is judged to be defective, it should be replaced replaced outright. This part of the chapter reviews the problems and solutions solutions for sound boards under both DOS and Windows. Windows. The following tips might help you nail down a sound problem most efficiently: s s s s s s s s s

Check to see that your speakers are connected, powered, and turned on. Check that the speaker volume and sound card master volume are turned up. Check to see that the mixer volume and master volume are set properly. Be sure that the music or sound file(s) are installed properly. Check that all sound card and multimedia drivers are installed. Be sure that the drivers are up to date. Check for resource conflicts between the sound card and other devices in the system. Be sure that the sound card is selected and configured properly (especially for DOS apps). The sound device should be enabled and configured under CMOS (for sound functions incorporated on the motherboard).

DRIVERS AND DRIVER ORDER Unlike most other expansion devices that are driven by system or supplemental BIOS, sound boards use small device drivers drivers to set up their operations. These drivers are genergenerally included in CONFIG.SYS and AUTOEXEC.BAT, AUTOEXEC.BAT, and are called when the system is first initialized. Most sound-board drivers are only used to initialize initialize and set up the board, so they do not remain resident—this is good because it would reduce the load on conventional and upper memory. However, these initiali initialization zation routines vary from board to board. For example, the files installed for a Creative Labs Sound Blaster will not support a Turtle Beach MultiSound board. board. If you elect to replace a sound board, you must also also disable any current sound-board drivers, and include include any new supporting driver files. The process is not difficult—just follow follow the installation instructions instructions for the board. But the software consideration does add another wrinkle to the replacement process. When there are problems installing or upgrading a sound board, one of the first issues to suspect is the driver loading order. Sound boards are typically multi-function multi-function devices that require several drivers in CONFIG.SYS CONFIG.SYS and AUTOEXEC.BAT AUTOEXEC.BAT.. If the drivers are in-

TROUBLESHOOTING A SOUND BOARD

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stalled in the wrong order, the sound board (or other features of the board) might not function. As a rule, the drivers should be loaded in the following order after your memory managers: s

The sound board’s device driver: DEVICE=C:.SYS /A:220

s

The CD-ROM port setup driver (if the sound board is equipped): DEVICE=C:.SYS /P:340

s

The CD-ROM driver (if the sound board is equipped): DEVICE=C:.SYS /D:MSCD001 /P:340 /A:0 /T:5 /I:11

FULL-DUPLEX DRIVERS Many current sound boards are compatible with “multimedia communication” technologies, such as Internet Phone, Phone, Webphone, and communication communication tools. These tools require full-duplex operation; that is, sound is digitized with the microphone and received sound is played through through the speakers simultaneously. simultaneously. This demands full-duplex drivers. drivers. If you plan to use communication tools, you’ll need to install full-duplex sound-card drivers that are appropriate for your particular particular sound board and operating system. For example, the Creative Labs SB32, AWE32, and AWE64 require the Windows 95 full-duplex driver file (SBW95UP.EXE) available from the Creative Labs Web site ( http:\www.creaf.com). To use those same devices for full-duplex under Windows NT 4.0, you’d need the AWENT40.EXE AWENT40.EXE driver file. As a rule, always check with the sound board maker maker for current full-duplex drivers. You might find that full-duplex drivers are not available for older sound boards or sound boards running under OS/2 OS/2 and Windows NT. In that case, you cannot cannot support full-duplex applications.

.WAV .WAV PLAYBACK PROBLEMS UNDER WINDOWS 95 Of all the sound-board problems reported, perhaps the most common is the failure to play wave files (ordinary sound files files with the .WAV extension) under Windows Windows 95. This problem usually manifests itself during the Windows startup or shutdown when the accompanying sounds are not played. A variety of issues can prevent prevent .WAV files from from playing. Program-specific problems If you cannot play .WAV files from a specific program

that you use in Windows 95, check to see if the same problem occurs when you play the file from another program. If the problem occurs only with one particular particular program, the files associated with that program might be damaged or that program might not be configured correctly under Windows Windows 95. If you cannot get .WAV files to play under any application, chances are that another issue is responsible.

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Sound device is not configured properly If you cannot play any .WAV files in

Windows 95 (or if .WAV files are not played at the proper volume), you might not have a sound device selected or the sound device that you have selected might not be configured properly. To select and configure a sound device device in Windows 95: s s

s s

Open the Control panel and panel and doubleclick the Multimedia the Multimedia icon. In the Playback the Playback area area under the Audio the Audio tab (Fig. 41-8), click the playback device that you want to use in the Preferred device list, then move the Volume slider to the value you want (usually 50 to 75% volume is adequate). In the Recording the Recording area area under the Audio the Audio tab, click the playback device that you want to use in the Preferred the Preferred device list, then move the Volume slider to the value you want. Be sure that the speakers are properly connected to the sound card and that the speakers are turned on.


The Audio tab under the Multimedia properties dialog.


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2 FIGUR FIGURE E 41-9 41-9

The multimedia Volume control applet.

Mixer settings are not configured properly If you cannot play any .WAV files

under Windows 95 (or if .WAV files are not played at the proper volume), the mixer control settings might not be configured configured properly. You can use the mixer-control program program included with Windows 95 to adjust the volume for playback, recording, and voice commands. To configure mixer control control settings for Windows Windows 95: s s

s

Click the Start button, button, point to Programs to Programs,, point to Accessories to Accessories,, point to Multimedia to Multimedia,, then click Volume click Volume control (Fig. control (Fig. 41-9). Be sure that the Mute the Mute all check all check box below the Volume control slider control slider and the “Mute” check box below the Wave slider are not selected, and that the Balance the Balance sliders for Volfor Volume control and control and Wave Wave are in the center of the scale. Move the Volume control and control and Wave Wave sliders at least halfway halfway to the top of the scale. You might need to adjust the current Volume control or control or Wave Wave settings to play .WAV files at the volume level you want.

If the Volume control and control and Wave Wave sliders sliders do not appear, click Properties Properties on on the Options menu, then click the Volume control and control and Wave Wave check check boxes in the “Show the following volume controls” box to select them. The sound hardware is not configured properly It is possible that your sound

card might not be compatible with the type of .WAV file you are attempting to play, or a resource conflict might be between your sound card and another device installed in your computer. Check the Device the Device manager to see if your sound board has any resource conflicts. To determine whether your sound card supports supports the .WAV file format you are attempting to play, contact the sound card’s manufacturer.


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The sound files are damaged If you cannot play certain .WAV files in Windows 95

(or if the .WAV files are not played properly), the .WAV files themselves might be damaged. To check if a .WAV file is damaged, use the right mouse button to click the .WAV file in Windows Explorer, click Properties Properties on the menu, then click the Details the Details tab. The Audio format line format line should contain information about the type of compression used to com press the file, the sound quality of the file, and whether whether or not the file is in stereo. If this information is missing, the .WAV file is probably damaged and should be reinstalled or recopied to the drive. If you can play other .WAV files of a similar format, chances are good that the suspect file is indeed damaged. If you can play .WAV files of different different formats, but not .WAV files of a particular format, it might be that your sound board does not support the particular format. Compression-related problems Windows 95 includes 32-bit versions of several

common CODECS including Adaptive including Adaptive Delta Pulse Code Modulation (ADPCM), (ADPCM), Interactive Multimedia Association (IMA) ADPCM , Group Special Mobile (GSM) 6.10, Consultative Committee for International Telephone and Telegraph (CCITT) G.711 A-Law and u-Law, and Truespeech from DSP. These 32-bit CODECS are installed installed by default during Windows 95 setup, and are used by multimedia programs—even programs—even if a 16-bit version of the same CODEC is available. available. Be sure that .WAV .WAV file format is suppor supported ted by an available CODEC. Otherwise, you might need to install an appropriate CODEC. CODEC.

SYMPTOMS Symptom 41-1. A noticeable buzz or hum is being produced in one or both speakers Low-cost speakers use unshielded unshielded cables. Unfortunately, strong strong signals from

ac cords and other signal-carrying conductors can easily induce interference in the speaker wires. Try rerouting speaker cables clear clear of other cables in the system. If problems persist, try using higher-quality higher-quality speakers with shielded cables and enclosures. enclosures. In most cases, that should resolve everyday everyday noise problems. If the noise continues, regardless of what you do, the fault might be in the sound-board sound-board amplifier. Try moving the sound board to another bus slot away from other boards or the power power supply. If that does not resolve the problem, try a new sound board. Symptom 41-2. No sound is produced by the speaker(s) The lack of sound

from a sound board can be caused by any one of a wide range of potential problems. If the sound board works with some applications, but not with others, it is likely that the problem is caused by an improperly installed or configured application. See that the offending application is set up properly (and be sure it is even capable of using the sound card). Also check that the proper sound driver files (if any) are loaded into CONFIG.SYS and AUTOEXEC.BAT, as required. In many cases, one or two sound-related environment variables that are set in AUTOEXEC.BAT. AUTOEXEC.BAT. Be sure that your startup files are configured properly. Check your speakers next. See that they are turned on and set to a normal volume level. The speakers should be receiving adequate power and should be plugged properly into the correct output jack—if speakers have been plugged into the wrong jack, no sound will be


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produced. If the cable is is broken or questionable, questionable, try a new new set of speakers. speakers. Also see that the master volume control on the sound board is turned up most (or all) of the way. If problems continue, a resource conflict might be occurring between the sound board and another device in the system. system. Examine the IRQ, IRQ, DMA, and I/O settings settings of each device in the system. system. Be sure that no two two devices are using the same resources. You might like to use the PC Configuration Form at the end of this book to record your settings. settings. If problems persist, and no conflict is present, try another sound board. Symptom 41-3. CD audio will not play through the sound card This problem

can occur under both DOS and Windows. First, be sure that the sound board is actually ca pable of playing CD audio (older boards might not be compatible). If the sound card is playing sound files, but is not playing CD audio, check several things. First, open the PC and be sure that the CD-audio cable (a thin, 4-wire cab le) is attached from the CD-ROM drive to the sound board. If this cable is broken, disconnected, or absent, CD audio will not be passed to the sound board. If the cable is intact, be sure that the CD audio player is configured properly for the sound board you are using, and check the startup files to see that any drivers and environment variables needed by CONFIG.SYS CONFIG.SYS and AUTOEXEC.BAT are available. If CD audio fails to play under Windows, be sure that an MCI an MCI (Multimedia Control Interface) CD Audio driver is included in the Drivers the Drivers dialog box under Windows Control panel . Symptom 41-4. An error, such as “No interrupt vector available” available” appears

The DOS interrupt vectors used by the sound board’s setup drivers (usually INT 80h to BFh) are being used by one or more other drivers in the system. system. As a consequence, there is a software conflict. Try disabling other drivers in the system one at a time until you see the conflict disappear. Once you have isolated the offending driver(s), driver(s), you can leave them disabled, or (if possible) alter their command-line settings so that they no longer conflict with the sound board’s software. Symptom 41-5. It has no MIDI output Be sure that the file you are trying to play

is a valid MIDI file (usually with a .MID extension). In most cases, you will find that the MIDI mapper under Windows is not not set up properly for the the sound board. Load the Windows MIDI mapper applet from the Control panel , and set it properly to accommodate your sound board. Symptom 41-6. Sound play is jerky Choppy or jerky sound playback is typically

the result of a hard drive problem—more specifically, the drive cannot read the sound file to a buffer fast enough. In most cases, the reason for this this slow drive performance is excessive disk fragmentation. fragmentation. Under DOS, the sound file(s) file(s) might be highly fragmented. fragmented. Under Windows, the permanent permanent or temporary swap files might be highly fragmented. In either case, use a reliable DOS defragmenter, such as PC Tools or Norton Utilities (leave Windows before defragmenting the disk), and defragment the disk thoroughly. Symptom 41-7. An error, such as “Out of environment space” appears

The system is out of environment space. space. You will need to increase the system’s system’s environment space by adding the following line to your CONFIG.SYS file: shell=c:.com /E:512 /P

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This command line sets the the environment space to 512 bytes. bytes. If you still encounter the ererror message, change the E entry to 1024. Symptom 41-8. Regular “clicks,” “stutters,” or “hiccups” occur during the playback of speech This might also be heard as a “garbled” sound in speech or sound

effects. In virtually all cases, the system CPU CPU is simply not fast enough to permit buffering without dropping sound data. Systems with i286 and slower slower i386 CPUs typically suffer with this this kind of problem. problem. This is often often compounded by insufficient memory memory (especially under Windows), which which automatically resorts to virtual memory. Because virtual memory is delivered by the hard drive and the hard drive is much slower than RAM anyway, the hard drive simply can’t provide data fast enough. Unfortunately, little little can be done in this kind of situation (aside from adding RAM, upgrading the CPU, or changing the motherboard). If it is possible to shut off various sound features features (i.e., music, voice, effects, etc.), try shutting down any extra sound features features that you can live without. Be sure that no TSRs or other applications are running in the background. Symptom 41-9. The joystick is not working or is not working properly on all systems This problem only applies to sound boards with a multi-function MIDI/joyMIDI/joy-

stick port being used in the joystick mode. Chances are that the joystick is conflicting with another joystick port in the system. Disable the original joystick port or the new joystick port—only one joystick port (game adapter) can be active at any one time in the system. Because joystick performance depends on CPU speed, the CPU might actually be too fast for the joystick port. Disable the joystick joystick port or try slowing the CPU CPU down. Symptom 41-10. The sound board is installed and everything works properly, but now the printer does not seem to work An interrupt conflict is be-

tween the sound board and an IRQ line used by the printer. Although parallel printers printers are often polled, they can also be driven by an IRQ line (IRQ5 (IRQ5 or IRQ7). If the sound board is using either one of these these interrupts, try try changing to an alternative alternative IRQ line. When changing an IRQ line, be sure to reflect the changes in any sound board files called by CONFIG.SYS or AUTOEXEC.BAT. Symptom 41-11. The following error message appears: “Error MMSYSMMSYSTEM 337: The specified MIDI device is already in use” This problem often oc-

curs with high-end sound boards, such as the Creative Labs AWE64. AWE64. This error is often caused by having the sound board’s mixer display on with the wavetable synthesizer selected (i.e., the LED display in the Creative Mixer turned on and Creative Wave Synthesizer selected as the MIDI playback playback device). You can usually correct the problem problem by turning the mixer display off. Symptom 41-12. The following error message appears: “Error: Wave device already in use when trying to play wave files while a MIDI file is playing” This problem often occurs with high-end sound boards, such as the Creative Labs

AWE64, and it is usually the result of a device configuration problem. If “full-duplex” is turned on and you try to play a .WAV file and a MIDI file at the same time with the wavetable synthesizer (e.g., the Creative Wave Synthesizer) selected as the MIDI play-


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back device, an error will occur. To resolve this problem, you need to turn off the full-dufull-du plex mode: Hold down key and doubleclick on My on My computer. computer. the Device manager tab. A listing listing for for Sound, Sound, video, game controllers should be s Select the Device included in the Device the Device manager, manager , doubleclick on the listing to expand it. s You should now see a listing for the sound board (e.g., Creative AWE32 16-Bit Audio). Doubleclick on the listing, then select the Settings tab. Un-check the box labeled Allow full-duplex operation. operation . Click OK Click OK until until you are back to the Control panel . s Now try to play a .WAV and MIDI file at the same time. s

Symptom 41-13. You hear “pops” and “clicks” “clicks” when recording sound under Windows 95 Cache is insufficient to adequately support the recording process (or cache

is improperly configured). Try the following procedure to alter the way cache is allocated: s s s

Open Notepad Open Notepad and and load SYSTEM.INI SYSTEM.INI Locate the area of SYSTEM.INI labeled [vcache]. Add the following line [vcache]: maxfilecache=2048

s s s s s

Save your changes to the SYSTEM.INI file. From the desktop, right-click on My on My computer, computer , then select Properties select Properties.. Select the Performance the Performance page, page, then click on File on File system . Find the slider marked Read-ahead Read-ahead optimization , then pull the slider to to None None.. Save your changes and restart Windows 95.

Symptom 41-14. You notice high frequency distortion in one or possibly possibly in both channels In many cases, the AT bus clock is set faster than 8MHz and data is

being randomly lost. This problem usually occurs in very fast systems using an ISA sound board. Enter the system’s CMOS CMOS setup and check the AT AT bus clock under the Advanced the Advanced chipset setup area. See that the bus clock is set as close close as possible to 8MHz. If the bus clock is derived as a divisor of the CPU clock, you might see an entry, such as /4. Be sure that divisor results in a clock speed as close to 8MHz as possible. possible. If problems still persist, persist, try increasing the divisor to drop the bus speed below 8MHz (this might have an adverse effect on other ISA peripherals). Symptom 41-15. You hear “pops” and “clicks” when playing back prerecorded files under Windows 95 An excessive processing load is on the system,

which is often caused by virtual virtual memory and/or 32-bit 32-bit access. Start by disabling virtual virtual memory: Open the Control panel and panel and doubleclick on the System icon. Select the Perforthe Performance page and click on Virtual memory. memory. Set the swap file to None and save your changes. Try the file playback again. If problems persist, persist, try disabling disabling 32-bit file access. If that still does not resolve the problem, try disabling 32-bit disk access. Symptom 41-16. “Pops” and “clicks” are audible on new recordings only, pre-existing files sound clean This is often caused by issues with software caching.

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If you are using DOS or Windows 3.1, disable SmartDrive from both CONFIG.SYS and AUTOEXEC.BAT, AUTOEXEC.BAT, then restart the computer for your changes to take effect. If problems continue (or you are using Windows 95), an excessive processing load on the system might be caused by virtual memory or 32-bit access. Follow the recommendations recommendations under Symptom 41-15. Symptom 41-17. “Pops” and “clicks” occur when playing back or recording any sound file In most cases, there is a wiring problem with the speaker system.

Check all of your cabling between the sound board and speakers. If the speakers are powpowered by ac, be sure that the power jack is inserted inserted properly. If the speakers are powered powered by battery, be sure that the batteries are fresh. Check for loose connections. If you cannot resolve the problem, try some new speakers. If the problem persists, replace replace the sound board. Symptom 41-18. The sound board plays back fine, fine, but it will not record

The board probably records fine in DOS, DOS, but not in Windows. If the sound board is using 16-bit DMA transfer (typical (typical under Windows), Windows), two DMA channels are in use. Chances are that one of those two DMA channels are conflicting with another device in the system. Determine the DMA channels being used under Windows, then check other devices for DMA conflicts. If you are using Windows 95, check check the Device the Device manager and look for entries marked with a yellow icon. Symptom 41-19. A DMA error is produced when using a sound board with with an Adaptec 2842 controller in the system This is a known problem with the Dig-

ital Audio Labs “DOC” “DOC” product and the Adaptec Adaptec 2842. You will need to alter alter the controller’s FIFO buffer. Go in the controller’s Setup by hitting + Open prompted during system system startup. startup. Select the Advanced the Advanced Configuration option, then select the FIFO threshold—chances are that that it will be set to 100%. Try setting the FIFO threshold threshold to 0% and see if this makes a difference. Symptom 41-20. A DMA error is produced when using a sound board with with an Adaptec 1542 controller in the system This is a known problem with the Dig-

ital Audio Labs “DOC” sound product and the Adaptec Adaptec 1542. The problem can usually be resolved by rearranging the DMA channels. Place the Adaptec controller on DMA 7, then place the sound board on DMA 5 for playback and DMA 6 for recording. Symptom 41-21. The sound card will will not play or record—the system just locks up when either is attempted The board will probably not play in either DOS

or Windows, but might run fine on other systems. systems. This is a problem that has been identified with some sound boards and ATI video boards. ATI video boards use unusual address ranges, which sometimes sometimes overlap the I/O address address used by the sound board. Change the sound board to another I/O address. Symptom 41-22. The sound card will record, but will not playback As-

suming that the sound board and its drivers are installed and configured properly, chances are that a playback oscillator on the sound board has failed. Try replacing the sound board outright.


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Symptom 41-23. The sound application or editor produces a significant number of DMA errors This type of problem is known to occur frequently when us-

ing the standard VGA driver that accompanies Windows—the driver is poorly written and cannot keep up with screen draws. Try updating your video driver to a later, more efficient efficient version. If the driver is known to contain bugs, try using a generic video driver that is written for the video board’s chipset. Symptom 41-24. The sound board will not record in DOS Several possible

problems can account for for this behavior. First, suspect a hardware hardware conflict between between the sound board and other devices in the system. system. Be sure that the IRQs, IRQs, DMA channels, and I/O port addresses used by the sound board are not used by other devices. If the hardware setup appears appears correct, suspect a problem problem between DOS drivers. drivers. Try a clean boot of the system (with no CONFIG.SYS or AUTOEXEC.B AUTOEXEC.BAT). AT). If sound can be run properly now, there is a driver conflict. Examine your entries in CONFIG.SYS CONFIG.SYS or AUTOEXEC.BAT TOEXEC.BAT for possible conflicts or for older drivers that might still be loading to sup port hardware that is no longer in the system. Finally, suspect the hard-drive hard-drive controller. Try setting up a RAM drive with RAMDRIVE.SYS. DRIVE.SYS. You can install a RAMdrive on your system by adding the line: device=c:.sys /e 8000

The 8000 is for 8MB worth of RAM—be RAM—be sure that enough RAM is in the PC. Once the RAMdrive is setup, try recording and playing from the RAMdrive (you might have to specify a new path in the sound-recorder program). If that works, the hard-drive controller might simply be too slow to support the sound board, and you might need to consider upgrading the drive system. Symptom 41-25. When recording sound, the system locks up if a key other than the recorder’s “hot-keys” are pushed This is a frequent problem un-

der Windows 3.1x. The system sounds (generated under Windows) Windows) might be interfering with the sound recorder. Try turning off system sounds. Go to the Main the Main icon, choose the Control panel , then select Sounds. Sounds. A box will appear in the lower left left corner marked En Enable system sounds. sounds. Click on this box to remove the the check mark, then click OK click OK . Symptom 41-26. After the sound-board driver is loaded, Windows locks up when starting or exiting In virtually all cases, you have a hardware conflict

between the sound sound board and another device in the system. Be sure that the IRQs, IRQs, DMA channels, and I/O port addressed used by the sound board are not used by other devices. Symptom 41-27. When using Windows sound-editing software, the sound board refuses to enter the “digital” mode—always switching back to the analog mode Generally speaking, this this is a software-configuration software-configuration issue. Be sure that

your editing (or other sound) software is set for the correct type of sound board (i.e., an AWE32 instead of a Sound Sound Blaster 16/Pro). If problems persist, the issue issue is with your sound drivers. Check the [drivers] section section of the Windows SYSTEM.INI SYSTEM.INI file for your

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sound-board driver entries. If more than one entry is listed, you might need to disable the competing driver. This is a known problem with the Digital Digital Audio Labs CardDplus, CardDplus, and it is caused by incorrect driver listings. For example, the proper CardDplus driver driver must be entered as: Wave=cardp.drv

and the companion driver must be listed as: Wave1=tahiti.drv

You will need to be sure that the proper driver(s) for your sound board are entered in SYSTEM.INI. You might also need to restart restart the system after making making any changes. Symptom 41-28. The microphone records at very low levels (or not at all)

Suspect that the problem is in your microphone. Most sound boards demand the use of a good-quality dynamic microphone. microphone. Also, Creative Labs Labs and Labtec microphones are not always compatible with with sound boards from other manufacturers. manufacturers. Try a generic dynamic microphone. If problems persist, chances chances are that your recording software is not configured properly for the microphone input. input. Try the following procedure procedure to set up the recording application properly under Windows 95: s s s s s

Open your Control your Control panel and panel and doubleclick on the the Multimedia Multimedia icon. The Multimedia The Multimedia properties dialog will open. Select the the Audio page. Audio page. In the Recording the Recording area, area, be sure to set the Volume slider all the way up. Also see that the Preferred the Preferred device and Preferred Preferred quality settings are correct. Save your changes and try the microphone again.

Symptom 41-29. The sound card isn’t working in full-duplex mode Virtu-

ally all current sound boards are capable of full-duplex operation for such applications as Internet phones. Check the specifications for for your sound board and see that the board is, in fact, capable of full-duplex operation. operation. If it is, and full-duplex isn’t working, your audio audio properties might be set up incorrectly: s s s s s s

Open your Control your Control panel and panel and doubleclick on the the Multimedia Multimedia icon. The Multimedia The Multimedia properties dialog will open. Select the the Audio page. Audio page. If the Playback the Playback device device and the Record the Record device device are set to the same I/O address, this is only half duplex. Change the Playback the Playback device I/O address, so it is different from the Record device. Record device. Hit the Apply the Apply button, button, then hit the OK button. button. You should now be in Full in Full duplex mode.

Some of the very latest sound boards (such as the Ensoniq SoundscapeVIVO 90) will carry full duplex operation with the same Playback and Playback and Record device Record device selected.


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Symptom 41-30. DMA errors occur using an older sound board and an Adaptec 1542 In many cases, you can clear DMA issues by slowing down the 1542 using

the /n switch. Add the /n switch to the ASPI4DOS command line in CONFIG.SYS, such as: device=c:.sys /n2

If slowing the 1542 down with an /n2 switch doesn’t fix the problem, then you should strongly consider upgrading the sound board. This is a known problem with the older Digital Audio Labs CardD sound board. Symptom 41-31. Hard-disk recording problems occur under Windows 95

Recorded audio is saved to your hard drive. For most systems, sound data can be transtransferred to the HDD fast enough to avoid any problems—if data transfer is interrupted, your recorded sound might “pop” or break up. Many factors affect HDD data-transfer data-transfer speed. The following sections sections outline a number of procedures procedures that might help you optimize a system for sound recording. recording. First, try disabling disabling the CD auto insert notification feature: s s s s s s

Go to the Device the Device manager Open the CD-ROM entry CD-ROM entry Select your CD-ROM drive, and click Properties Properties Go to the Settings page Settings page Uncheck the Auto the Auto insert notification box notification box Select OK

Next, try turning down the level of graphics acceleration: s s s s s s

Right-click on the My the My computer icon Left-click on Properties on Properties Select the Performance the Performance page page Select the button labeled Graphics labeled Graphics Start by turning down the acceleration one notch (you can return later to turn it down further if more performance is required) Select OK It might also be necessary to adjust the size of your virtual memory swap file:

s s s s s s

s

Right-click on the My the My computer icon Left-click on Properties on Properties Select the Performance the Performance page page Select the button labeled Virtual labeled Virtual memory Choose Let Choose Let me specify my own virtual memory settings If your PC has 16MB of RAM, set the minimum minimum and maximum at 40MB. If you have 32MB of RAM, set the minimum and maximum at 64MB. Select OK

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Try removing any active items from your Startup group: s s s s s s s s

Click the Start button button Go to the Programs the Programs menu, then select Startup. Startup. If you see anything anything here, it it might be hurting your system performance. Eliminate anything that is not absolutely necessary. To remove items, click the Start button, button, go to Settings, Settings, then select Taskbar Choose the page labeled Start labeled Start menu programs Click the Remove the Remove button button Open the Startup group by doubleclicking it Remove any items that you feel are not necessary and are wasting resources Select the Close button Close button when finished Clear any indexes of the Find Fast utility:

s s s s s s s s

Click the Start button button Go to Settings, Settings, then choose the Control panel Open the Find the Find Fast utility Fast utility Go to the Index the Index menu Select Delete Select Delete index Select an index in the In the In and below drop box Select the OK button button Repeat steps 5 through 7 until all indexes are removed Try defragmenting the hard drive:

s s s s s

Click the Start button button Go to Programs to Programs,, Accessories, Accessories, and System and System tools Choose Disk Choose Disk defragmenter Select the drive to defragment and click OK click OK Click the Start button button to begin defragmentation Finally, you might want to suspend the System Agent (if installed):

s s s s

If System Agent is installed, open it by doubleclicking its icon in the taskbar Go to the Advanced the Advanced menu menu Choose Suspend system agent Close the System agent window. agent window.

Symptom 41-32. The microphone records only at very low levels or not at all Check your phantom power settings settings first. In many cases, the microphone’s microphone’s gain is set

too low in the sound board’s mixer mixer applet. Start the sound board’s board’s mixer, be sure that the microphone input is turned on, then raise raise the microphone’s level control. control. Remember to save the mixer settings before exiting exiting the mixer. You should not have to restart the system. Symptom 41-33. The dynamic microphone clips terribly, and recordings are noisy and faint This is probably caused by phantom power being switched on in

FURTHER FURTHER STUDY

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your sound board. Try turning the phantom phantom power off. If you cannot turn phantom phantom power off, try plugging the dynamic dynamic microphone into the sound board line input jack. jack. Remem ber to start the sound board mixer applet and set the line input level properly. Symptom 41-34. Trouble occurs when using Creative Labs or Labtec microphones with your (non-Creative Labs) sound board This is a common com-

plaint among Ensoniq Ensoniq sound board users. It turns out that Ensoniq Ensoniq sound boards are not compatible with Creative Labs or Labtec microphones. microphones. Try a generic microphone instead. Symptom 41-35. Static is at the remote end when when talking through a voice application, such as WebPhone Noise is occurring at the line input or microphone

input, which is being transmitted transmitted to the remote remote listener. Check the line input signal. You might try reducing or turning off the line line input mixer level. If the problem persists, check your phantom power setting and your microphone. microphone. Try reducing the microphone level in in the sound board’s mixer. Try a different microphone. microphone.

Further Study This concludes the material material for Chapter 41. Be sure to review the glossary and chapter questions on the accompanying CD. CD. If you have access to the Internet, take a look at some of these sound-board resources: Creative Labs: http://www.creaf.com Turtle Beach: http://www.tbeach.com/ Frontier Design Group: http://www.frontierdesign.com/ Ensoniq: http://www.ensoniq.com SIC Resource: http://www.sicresource.com/ Star Multimedia: http://www.starusa.com/

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