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BOOT CAMP 241 (03/09/02)
SPEAKERS AND SOUNDCARDS part 1
Computer sound has come a long way in a comparatively short
time. First generation PCs could only manage the occasional bleep from a tiny
internal speaker, usually only booting up or when something went wrong. It
wasn’t a problem since throughout the eighties PCs were mostly confined to
mundane office applications and they remained effectively mute until the launch
of Windows 3 in 1990 but even then a sound adaptor and speaker – stereo was
still to come – were considered optional extras.
Since then sound has become an integral part of the PC
specification and nowadays virtually all PCs and laptops come with an audio
capability as standard. The supplied components are usually fine for reproducing
the sounds made by Windows and most office applications but if you want to
explore the multimedia capabilities of your machine, play games, make or listen
to music, it is almost certainly worthwhile replacing your PCs speakers, and
probably the sound adaptor as well. This week we’ll look at how your PC makes
noises, next week, how to make it sound even better.
PC sound evolved haphazardly over a number of years,
resulting in a bewildering number of systems and standards. Anyone who has been
around PCs for more than a few years will clearly remember the fun and games
involved in getting AdLib and SoundBlaster devices to work. Fortunately for most
users there’s no need to get involved with the intricacies, unless you are a
dedicated games buff or musician, in which case you should pay a visit to a web
site like http://www.pctechguide.com/11sound.htm,
which explains the technicalities in some detail.
Nevertheless, it doesn’t hurt to know a little about how PC
sound works so we’ll begin with a short tutorial. All of the sounds coming from
a desktop PC – apart from the boot-up bleep(s) made by an internal speaker --
are channelled through a device called a sound card or adaptor. Usually it is a
separate circuit board or module that plugs into an expansion slot on the
computer’s motherboard though on a lot of machines built within the last five
years or so sound adaptor chips are incorporated into the motherboard. On some
high-end set-ups it may be a separate module – usually housed in a spare disc
drive bay -- connected to the motherboard by a ribbon or data cable.
Most soundcards -- integrated and stand-alone -- do at least
four things: synthesise sounds, convert analogue sound into digital data (A to
D), convert digital data into analogue sound (D to A) and provide a connection
for electronic musical instruments and joysticks via a ‘midi’ (musical
instrument digital interface) socket.
The synthesiser section creates sounds under instruction from
a software program or hardware device, like a keyboard. There are two common
methods: FM Synthesis, where sounds are made by mixing electronically generated
tones or ‘voices’; and Wavetable, which uses sampled or digitised sounds,
recorded from real instruments. There are other systems but in general cheaper
soundcards and integrated adaptors use FM synthesis whilst the more expensive
ones use the Wavetable method
Analogue to digital conversion is used for recording sounds
on a PC, from a microphone or from an external input, such as a tape deck, CD
player, radio etc. The incoming analogue sound signal enters via the microphone
or ‘line input’ socket on the soundcard or motherboard and is converted into
digital data by the soundcard then processed by software or stored in a file, on
the PC’s hard disc drive. Digital to
analogue conversion reverses the process and turns digital data generated by
programs on the PC, or stored on the hard disc drive, into audible sounds.
Incidentally, most soundcards have a low power amplifier built in, so they can
drive small speakers directly though the majority of PC speakers these days have
their own built-in amplifiers – more on that next week.
The midi interface is an industry-standard connection system
that allows a wide range of electronic instruments, keyboards, drum machines and
so on (some traditional musical instruments also have midi interfaces) to be
connected to a PC and used in conjunction with specialist composing and
recording software.
Sound on a multimedia PC can originate from a wide variety of
sources, however, in many cases the soundcard has comparatively little influence
on the final audio quality. By far the most common sounds are the bleeps, pings
and tinkly tunes generated by Windows and other programs. These are mostly in
the form of wave or ‘*.wav’ files, which are basically digitised samples; the
soundcard converts them into analogue sound signals so no synthesis is involved,
in other words the sound you hear is contained in the actual sound file and not
generated by the soundcard.
Soundcards also have relatively little influence on quality
when playing audio CDs or MP3 files. Music on an audio CD is stored as digitised
samples – similar to *.wav files – but in most set-ups the data on the disc is
converted into an analogue audio signal by the actual CD-ROM drive and then fed,
via a screened cable, to the soundcard or adaptor (a few high-end CD/DVD-ROM
drives also have digital outputs). All the soundcard has to do is pass the
signal though a pre-amplifier stage (volume and tone control etc.) then on to
the loudspeaker output. MP3 files go through a slightly different process, they
are also digitised samples but the data is highly compressed. The files are
first decompressed by separate ‘player’ software then the data is fed to the
sound card’s digital to analogue converter before going to the speaker
output.
Soundcard performance only really starts to become
significant when the PC is used for making music or playing games, especially
action games which rely heavily on ‘synthesised’ background music, dramatic
effects or generate 3D and multi channel surround soundtracks.
Next week – Speakers and soundcards, part 2
JARGON FILTER
ADLIB
Early PC soundcard standard now largely superseded by the
SoundBlaster standard introduced by Creative Labs in 1989
MP3
Motion
Picture Experts Group audio layer 3 -- digital audio compression system commonly
used to send files containing audio and music over the
Internet
SAMPLE
A digital recording of a sound which can be manipulated to
change pitch, tone and timbre
TOP TIP
If you are wondering how well protected your PC is against
hackers then you should pay a visit to the following web page: http://browsercheck.qualys.com/. The
site carries out a series of checks on your browser to see how vulnerable it is
to attack. All of the tests are safe and non-destructive (but follow the advice
and back up valuable data, the results can be disturbing). At the very least it
will probably be able to extract details of your PC hardware, you may even find
that an intruder could gain access to the files on your hard drive, read the
contents of your clipboard and even run programs – it’s scary stuff so check it now, before
it’s too late!
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