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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