Components of a
PC Sound System
These components are common to PC
sound systems:
l Sound card: The sound card
combines all the inputs, outputs, and signal processors required to convert
audio information into and from digital form into a single card. Sound cards
are either ISA or PCI adapter cards or can be integrated directly on the
motherboard through an audio chip.
l Amplifier: After the sound
card has converted digital audio into an analog (audible) signal, the signal
must be amplified before it can be played back on speakers. Most sound cards
include a weak amplifier that is capable of driving a set of headphones or a
set of small PC speakers. Some PC speakers include an amplifier in one or both
of the speakers, which takes the burden off the sound card.
l Speakers: PC speakers are
available as small passive systems that are powered from the sound card's
headphone output or as active (amplified) 3-way surround-sound systems that
rival many home theatres and somewhere in-between. Some computer monitors have
speakers that are integrated into their bezels or that snap onto their sides.
USB speaker systems do not require a separate sound card--all the sound
processing is contained inside the speaker itself.
Turning on to
sound cards
The sound card combines the
components required to transfer sound into and out of a PC, including:
l Analog input
jacks: Most
sound cards have line-level and a mic-level inputs. Line-level inputs accept
signals from electronic sources such as a CD player or directly from a musical
instrument like a synthesizer. Mic-level inputs accept the signal from a
microphone or an unamplified electric guitar.
l Analog output
jacks: Nearly
all sound cards have speaker out and line out analog output jacks. A small
amplifier drives the speaker out jack and its output level is
appropriate for a pair of headphones or PC speakers. The line out jack
provides a line-level signal that can be used as an input to another sound device,
like a stereo receiver.
l Analog to
Digital Converter (ADC): The ADC converts analog audio data, such as a live
voice or a musical instrument, into digital data that can be stored on a PC.
l Digital I/O
jack: This
jack, if present, allows digital devices to be directly connected to the PC and
digital audio signals to be passed without being converted to analog.
l Digital Signal
Processor (DSP): A
feature once reserved for high-end sound cards, a digital signal processor
(DSP) is now common on most newer sound cards. A DSP reduces the load on the
PC's CPU for processing audio.
l Digital to
Analog Converter (DAC): The DAC converts stored digital audio data into
audible (analog) information that can be played back on speakers or headphones.
l Game/MIDI port: This
dual-purpose connector, which is found on many sound cards, is used for game
controllers such as joysticks and, through a special cable, can be connected to
any external MIDI.
l Synthesizer: Many of the
sounds that a sound card produces are generated on the card using a synthesizer
chip.
Listening to
sound files
A variety of audio file types can
be stored and played on a PC. Audio file types typically go by their file extensions.
Here are the most common audio file types:
l AAC: AAC is the
compression standard expected to succeed MP3. AAC (Advanced Audio
Coding) is another name
for MPEG-2, which should not be confused with MP2.
l AIFF: AIFF (Audio
Interchange File Format) is the Macintosh equivalent of the Windows' WAV format.
This format can be played on a PC with the Windows Media Player.
l AU: AU is the UNIX
audio file standard. Most Web browsers have built-in AU support, and newer
versions of the Windows Media Player can play back AU files.
l MID: MID aren't really
digital audio files; they contain MIDI data, which includes information such as
the pitch and duration of each note.
l MP3: Short for MPEG-1
Layer 3, MP3 is an audio compression standard developed by the Moving
Pictures Experts Group (MPEG). MP3 compression has become popular because file sizes
can be greatly reduced while retaining most of the original WAV file's sound
quality.
l RA or RAM: Real Networks
developed these file formats for streaming audio files. Real Audio files require
a dedicated Real Audio player or browser plug-in for playback.
l WAV: WAV is the standard
Windows audio file format with recording and playback support built into the
Windows operating systems.
l WMA: Windows Media
Audio is
Microsoft's answer to Real Audio. WMA files can be played back on Windows Media
Player and many other sound players.
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