Chapter 18

Sound

MELJUN CORTESMELJUN CORTES

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OverviewIn this chapter, you will learn to

Describe how sound works in a PC

Select the appropriate sound card for a given scenario

Install a sound card in a Windows system

Troubleshoot problems that might arise with sound cards and speakers

How Sound Works in a PC

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Sound-Capture Basics Four components for capturing and

outputting sound1. Sound card2. Speakers3. Microphone4. Recording/Playback software

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Sound-Capture Basics Sampling—capturing sound

Sampling rate is measured in cycles per second (KHz)Low quality (11 KHz) to high quality (192 KHz)

Doesn’t capture every nanosecond of sound

Takes samples and extrapolates, or predicts, what the data is between samplesDotted line—can you connect the dots?

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Sound-Capture Basics Sampling—capturing sound

Bit depth—Number of characteristics of a particular sound (for each sample)

Amplitude (loudness)

Frequency (tone)

Timbre (qualities from different instruments)

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Sound-Capture Basics Waveforms are commonly sampled with either 8 or

16 bits per sample8-bit stores 28 or 256 different characteristics16-bit stores 216 or 65,536 different characteristics

TracksMonaural—one trackStereo—two tracks

CD quality44.1 KHz16 bit depth

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Recorded Sound FormatsPulse code modulation (PCM)

Developed for telephone calls

Better known as the WAV format

Large files Four-minute song at 44.1 KHz and 16-bit stereo is greater

than 40 MB

Compressor/decompressor (CODEC) programs Algorithms developed to compress sound files MPEG-1 Layer 3 codec or MP3 is one example of a codec

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Playing SoundsEvery sound card can play WAV files using

sound player softwareWindows Media Player comes with WindowsiTunes is Apple’s media programMany other good sound players are available

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MIDI Musical Instrument Digital Interface

MIDI file is a text file

Contain a series of commands that describeWhat note to playHow long to play itWhich instruments to use

Tiny in size compared to WAV filesBeethoven’s Fifth Symphony is 78 MB as a

WAV file and 60 KB as a MIDI file

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MIDI Sound cards play MIDI files using one of two

technologies

1. FM synthesis• Strictly electronic—software says what to play

2. Wave table synthesis• Uses recorded sounds (WAV files) to start• Modifies characteristics of sounds to create

amplitude, frequency, and timbre desired• Polyphony of card—how many instruments it can

play at once (128 instruments is common)

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Other File FormatsOver 100 sound formats

Table lists just a fewAcronym DescriptionAAC Advanced Audio Coding—native format for Apple’s

iTunesAIFF Audio Interchange File Format—popular with

Macintosh computersASX Microsoft Advanced Streaming RedirectorAU Can be played in Windows, Sun, Next, UNIX and

MacintoshOGG Vorbis format—open source codexRM RealMedia—audio, or audio and videoWMA Windows Media Audio—proprietary

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VideoVideos typically have sound built in

Some common video formats are

Acronym DescriptionAVI Audio Video InterleaveMPEG Moving Pictures Experts GroupMOV QuickTimeASF Advanced Streaming FormatRM Real MediaWMV Windows Media VideoDivX Often used for ripping audio and videoFlash Used on YouTube

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ApplicationsMany applications (especially games) play

sounds

Most use the standard WAV, MP3, or MIDI file formats

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Streaming MediaBroadcast of data that is played on your

computer and immediately discardedInternet radio stationsMost popular players are

Windows Media PlayerWinampApple’s iTunes

CompTIA A+Essentials

Essentials

Getting the Right Sound CardGetting the Right Sound Card

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Sound Cards A sound card typically has many built-in

featuresTwo separate processors (one for MIDI and

one for the rest)Support chips for joysticksRecording capabilitiesMIDI supportMore

Can be a separate sound cardOften just a chip built in to the motherboard

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Sound Card DifferencesSound cards differ in five basic areas:

- Processor capabilities - Speaker support- Recording quality - Jacks- Extra features

Processor handles communication between the application, OS, and CPULow-end sound cards let your CPU do most of

the workBetter sound cards do most of the processing,

which accelerates the sound process and provides better sound quality

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Sound Card DifferencesSpeaker support

Basic support—two speakers or headphones

Better sound cards support five or more speakers

Often have a subwoofer5.1 means 5 speakers with 1 subwoofer

Recording qualitySignal-to-noise (S/N) ratio expressed in decibelsLow end have S/N ratio of 30 to 50 decibels

Records artifacts (noise) when there is no actual noiseHigh-end cards offer a 96 to 100+ S/N ratio

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Sound Card DifferencesJacks

Line In and Line Out converters enable the sound card to send and receive input and output from other devices

The Line In connector runs to a Line Out or Aux connector on the back of a stereo receiving system

Rear Out connects to the rear speakers for surround sound

Analog/Digital Out for external digital connections

Microphone & Joystick

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Sound Card Connections Main stereo speaker is blueLine out connector is greenMicrophone connector is pink

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Sound Card DifferencesExtra Features

Almost all motherboards have built-in soundExtra goodies needed to entice buyersDigital output to integrate PC with home

entertainment systemDVD receiverSurround-sound speaker connectionsBreakout box adding ports to front of PCMore

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Audio CablesTo play audio CDs through your sound card

requires a cable from your optical drive to the sound card

Most optical drives come with an MPC2 audio cable for this purpose

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Speaker StandardsStereo

Left and right

2.1 systemsPair of speakers called

satellites and a subwoofer

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Surround-Sound Standards Dolby Digital

Supports five channels plus subwoofer (5.1)Front right, front left, front center, rear left, rear right

Digital Theatre System (DTS)Competing standard that also supports 5.1

Sony/Philips Digital Interface (S/PDIF) Uses single connector for entire 5.1 system

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Surround-Sound StandardsDirectX provides applications, primarily games,

with direct access to hardwareOffers developers easy-to-use commandsEasy to program sounds in the desired channel

DirectSound3D (DS3D)Can place a sound anywhere in 3D space Known as positional audio

Environmental audio extensions (EAX)Creative Labs’ response to DS3D

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Speaker FeaturesControls

Volume controllersOn/off switchCan be on speakers

or on special box

Headphone jackSome systems

can automaticallysense when plugged in

Installing a Sound Card in a Windows System

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Physical InstallationInstalls like any other PCI card

Plug in the cardLoad the driversTest

Hardest part may be identifying where to plug in speakersRefer to documentationTypical stereo or 2.1 speaker system plugs

into Speaker or Speaker 1 portSurround-sound speakers use single S/PDIF

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Physical InstallationBasic steps

Shut down your computer, unplug it, and open the case

Find an open PCI slot and install cardConnect the CD audio cable to the drive and

the card

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Installing Drivers Let Windows install drivers

If necessary/desired, use CD that came with sound card

If installing a USB sound cardFollow the cardinal rule for USB drivers:

Install the USB driver before the USB device

Verify driver is installed by checking Device Manager

Test

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Configuration ApplicationsMost sound card configurations can be done

within WindowsUse the Sounds and Audio Devices applet in

Windows XP’s Control PanelOr Sounds and Multimedia in

Windows 2000 Five tabs

Volume Sounds Audio Voice Hardware

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Proprietary Configuration AppsMany sound cards install proprietary

softwareAdds access to other features that aren’t

otherwise available

Autosensing—allows hardware to be plugged in using different ports and the ports adjustPlug microphone into speaker port and speaker port

becomes a microphone port

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Installing ApplicationsSome sound cards install extra software

Goal is to provide user with extra free software

These programs aren’t needed to use any of the features

Intended to provide extra value for the purchase

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IT TechnicianCompTIA A+Technician

Troubleshooting Sound

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Hardware ProblemsVolume

Check physical controlsCheck software controls

Windows Volume controls

SpeakersEnsure they are turned on and getting good

powerMake sure they are plugged inCheck for visual indicators that a sound is

playingReplace speakers if blown speakers suspected

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Configuration ProblemsFirst place to check: Device Manager

Consider reinstalling driver

Ensure the latest device drivers are installedCheck the manufacturer’s

Web site for updates

Review the Sounds and Audio Devices applet settings

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Application ProblemsFirst, look for an

error messageCheck the application’s

support site

Second, check the sound fileSound files might be corrupted

Last, reinstall the application

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Beyond A+Sound card benchmarking

PC performance issues may be related to your sound card

Analyze your sound card with RightMark 3DSound from iXBT.Com/Digit-Life

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