One of the problems with the PC standard is that when it
was first created, it did not include audio capabilities other
than rudimentary beeping or tone generation. Part of this was
due to the fact that the PC standard originated in 1981, and
other computers of that time had similar rudimentary
capabilities. Systems that were designed later, such as the
Macintosh which debuted in 1984, did include high-quality
audio capabilities as an integral part of the system hardware
and software. Although there still is no universal audio
hardware and software standard for PC-compatible systems, the
inherent expandability of the PC platform allows audio
capability to be easily added, and at least one de facto
standard has emerged. This chapter focuses on these products
and how they are installed and operated.
Sound Card Applications
At first, consumer sound cards were used only for games.
Several companies including AdLib, Roland, and Creative Labs
had introduced products by the late 1980s. In 1989, Creative
Labs introduced the Game Blaster, which provided stereo sound
to a handful of computer games. The question for many buyers
was, "Why spend $100 for a card that adds sound to a $50
game?" More importantly, because no sound standards existed at
the time, a sound card might be useless with other games.
NOTE: About the same time, the Musical
Instrument Digital Interface (MIDI) interfaces became
available for the PC, but were used in very specialized
recording applications.
A few months after releasing the Game Blaster, Creative
Labs announced the Sound Blaster sound card. The Sound Blaster
was compatible with the AdLib sound card and Creative Labs'
own Game Blaster card. It included a built-in microphone jack
and a MIDI (Musical Instrument Digital Interface) for
connecting the PC to a musical synthesizer. Finally, the sound
card had uses other than games.
Unfortunately, there is no single standard for
PC-compatible sound cards. As in other aspects of the computer
industry, standards are often developed by the market leader
in a particular segment of the marketplace. These are called
de facto standards. For example, Hewlett-Packard
printers use a command language and graphics language that has
become a de facto standard simply because many of their
printers have been sold and most software supports them. Other
printer manufacturers then strive to make their printers
emulate the Hewlett-Packard printers so they don't require
unique commands and they can use the same commands and drivers
as a Hewlett-Packard printer. This is how a de facto standard
is born. It is essentially based on popularity. While other
printer command standards exist, the Hewlett-Packard standard
is supported by most PC-compatible printers.
Over the last few years, several sound card manufacturers
have fought for dominance, and there are several popular
brands. Although several different companies make audio
boards, the ones from Creative Labs have dominated the
marketplace and have become the de facto standard. Thus, most
audio boards from other companies emulate the Creative Labs
Sound Blaster boards. Like the Hewlett-Packard printer
standard, the Creative Labs Sound Blaster interface is the one
that most hardware products emulate, and the one that most
drivers are written for.
A sound card has many uses, including the following:
- Adding stereo sound to entertainment (game)
software
- Increasing the effectiveness of educational software,
particularly for young children
- Adding sound effects to business presentations and
training software
- Creating music by using MIDI hardware and
software
- Adding voice notes to files
- Adding sound effects to operating system events
- Enabling a PC to read
- Enabling PC use by handicapped individuals
- Playing audio CDs
Games
The sound card was originally designed to play games. In
fact, many sound cards include a game adapter
interface, which is a connector for adding a game control
device (usually a joystick or control paddles). This is a
potential area of conflict because other cards such as the
multi-I/O type cards used in many PCs that have serial ports,
parallel ports, and so on also have a game interface. This
will result in an I/O Port address conflict since all game
interfaces use the same I/O Port addresses. In these cases, it
is usually best to use the game adapter interface on the sound
card and disable any other in your system.
By adding a sound card, the game playing takes on a new
dimension. The sounds add a level of realism that would
otherwise be impossible, even with the best graphics. For
example, some games use digitized human voices and dialog. In
addition to realistic sounds and effects, games can have
musical scores, which add to the excitement and entertainment.
Multimedia
A sound card is a prerequisite if you want to turn your PC
into a Multimedia PC (MPC). What is multimedia? The
term embraces a number of PC technologies, but primarily deals
with video, sound, and storage. Basically, multimedia means
the ability to merge images, data, and sound on a computer. In
a practical sense, multimedia simply means adding a sound card
and a CD-ROM drive to your system.
An organization called the Multimedia PC Marketing Council
was originally formed by Microsoft to generate standards for
MPCs. The council created several MPC standards and license
its logo and trademark to manufacturers whose hardware and
software conform to these standards. This allows compatible
hardware and software to be developed for multimedia operation
on PC-compatible systems.
More recently, the MPC Marketing Council has formally
transferred responsibility for its standards to the Software
Publishers Association's Multimedia PC Working Group. This
group includes many of the same members as the original MPC,
and will now be the body governing the MPC specifications. The
first thing this group has done is create a new MPC
standard.
The MPC Marketing Council originally developed two primary
standards for multi- media. They are called the MPC Level
1 and MPC Level 2 standards. Now under the
direction of the Software Publishers Association (SPA), these
first two standards have been augmented by a third standard
called MPC Level 3, which was introduced in June 1995.
These standards define the minimum capabilities for an MPC.
Table 12.1 shows these standards.
Table 12.1 Multimedia Standards
|
MPC Level 1 |
MPC Level 2 |
MPC Level 3 |
Processor |
16MHz 386SX |
25MHz 486SX |
75MHz Pentium |
RAM |
2M |
4M |
8M |
Hard Disk |
30M |
160M |
540M |
Floppy Disk |
1.44M 3 1/2-inch |
1.44M 3 1/2-inch |
1.44M 3 1/2-inch |
CD-ROM Drive |
Single-Speed |
Double-Speed |
Quad-Speed |
Audio |
8-bit |
16-bit |
16-bit |
VGA Video |
640x480; |
640x480; |
640x0; |
Resolution |
16 colors |
64K colors |
64K colors |
Other I/O |
Serial, Parallel, MIDI, Game |
Serial, Parallel, MIDI, Game |
Serial, Parallel, MIDI, Game |
Software |
Microsoft Windows 3.1 |
Microsoft Windows 3.1 |
Microsoft Windows 3.1 |
Date Introduced |
1990 |
May 1993 |
June 1995 |
The MPC-3 specifications should be considered the bare
minimums for any multimedia system today. In fact, I would
normally recommend a system that exceeds the Level 3 standards
in several areas, such as CPU, RAM, hard disk size, and video
capability. Note that although speakers are technically not a
part of the MPC specification, they are certainly required for
sound reproduction!
MIDI
If you're musically inclined, you'll enjoy MIDI (Musical
Instrument Digital Interface). Developed in the early
1980s, MIDI essentially is a powerful programming language
that lets your computer store and edit or play back music in
tandem with a MIDI-compatible electronic musical instrument,
typically a keyboard synthesizer.
The MPC specs mentioned earlier call for MIDI support. With
MIDI, you can compose and edit music for presentations, learn
about music theory, or turn your PC into a one-stop music
mixing studio.
MIDI makes a musical note sound as though it comes from any
of a wide array of instruments. The MPC specifications require
a sound card to contain an FM MIDI synthesizer chip and be
able to play at least six notes simultaneously.
To connect a MIDI device to a PC, you need a sound card
that has two round serial ports in back--a MIDI input port and
a MIDI output port. In addition to a keyboard, you'll need
sequencing software to modify the tempo, sound, and volume of
your recordings, or to cut and paste together various
prerecorded music sequences.
Unlike other sound files, MIDI messages require little disk
space. An hour of stereo music stored in MIDI requires less
than 500K. (To contrast, a Microsoft Windows digital sound WAV
file consumes more than 1,000 times that space.) Many games
use MIDI sounds to conserve on disk space.
The quality of sound reproduction from MIDI files can vary
greatly from card to card. This depends largely on whether
your card uses wavetable synthesis or FM synthesis for MIDI
reproduction.
Most sound boards generate sounds by using FM
synthesis, a technology first pioneered in 1976. By using
one sine wave operator to modify another, FM synthesis creates
an artificial sound that mimics an instrument. Over the years,
the technology has progressed (some FM synthesizers now use
four operators) to a point where FM synthesis sounds good, but
it still sounds artificial.
More realistic, inexpensive sound was pioneered by Ensoniq
Corp., the makers of professional keyboards, in 1984. Using a
technology that had been theorized at about the same time as
FM synthesis, Ensoniq found a way to sample any
instrument--including pianos, violins, guitars, flutes,
trumpets, and drums--and to store the digitized sound in a
wave- table. Stored either in ROM chips or on disk, the
wavetable supplies an actual digitized sound of an instrument
when called by the application. Soon after Ensoniq's
discovery, other keyboard makers replaced their FM
synthesizers with wavetable synthesis.
Wavetable synthesis won't make every sound on your PC more
realistic--only the MIDI sounds, which are often used in
games. Windows WAV files are actual stored sounds and don't
benefit from wavetable synthesis.
Presentations
Businesses are discovering that combining graphics,
animation, and sound is more impressive, and often less
expensive, than a slide show. A sound card adds impact to any
presentation or classroom.
A variety of business-presentation software and high-end
training and authoring packages already exist. And you don't
have to be a programmer to get your own show on the road. Even
such popular software packages as CorelDRAW! and PowerPoint
now include sound and animation features for their
presentation files.
Some presentation software, such as PowerPoint and Corel
Presents!, packages support WAV, AVI, and MIDI files. With
these products, you can synchronize sounds with objects. When
a picture of a new product is displayed, for example, you can
play a roaring round of applause. You can even pull in audio
from a CD in your CD-ROM drive. Such presentation software
programs often include clip-media libraries.
A sound card can make tasks (such as learning how to use
software) easier. PC software manufacturers have taken an
early lead in this area. Many publishers are shipping special
CD-ROM versions of some of their products. These versions
often include animated online help, replete with music.
You can even take your show on the road. Many laptop and
notebook computers today include sound capability and even
have built-in CD-ROM drives and speakers. There are also
external sound cards and even CD-ROM drives that attach to a
laptop computer's parallel port to provide multimedia on the
go. Finally, there are also several PC Card (PCMCIA)-based
sound cards and CD-ROM drives on the market.
Recording
Virtually all sound cards have an audio input jack. With a
microphone, you can record your voice. Using the Microsoft
Windows Sound Recorder, you can play, edit, or record a sound
file. These files are saved as WAV files, a type of
file format. In the Windows Control Panel, you can assign
certain Windows events a specific WAV file (see Figure 12.1).
I always get a laugh when I exit Windows and hear the sound of
a flushing toilet!
By recording your own sounds, you can create your own WAV
files. Then you can use them for certain events. These are
some of the standard events:
Start Windows |
Menu Command |
Menu Pop-up |
Exit Windows |
Default Sound |
Exclamation |
Open Program |
Asterisk |
Maximize |
Close Program |
Critical Stop |
Question |
Minimize |
Program Error |
|
FIG.
12.1 The Sounds section of the Windows
95 Control Panel adds sound to different Windows
events.
Through the same audio input jack, you can attach your
stereo system and record a song to a WAV file. You can also
purchase prepackaged WAV files. Prerecorded WAV files can also
be found on your local electronic bulletin board or online
services such as CompuServe and America Online.
You can find audio files, particularly WAV files, at
several locations such as:
Voice Annotation
By using WAV files, you can record messages into your
Windows documents and spreadsheets. For example, a business
executive could pick up a microphone and, by embedding a
message in a contract, give his or her secretary explicit
instructions. This message is called a voice
annotation. I like to think of it as a verbal Post-It
note.
With voice annotation, you can embed voice messages,
suggestions, or questions in a document and send it to a
colleague. To leave such messages, your Windows application
must support Windows' Object Linking and Embedding (OLE).
Imagine that you're editing a worksheet in Excel and want
to insert a voice note next to a total that looks
questionable. Place the cursor in the cell next to the total,
then select Edit, Insert, Object, Sound to call up Windows'
Sound Recorder. Click the Record button and begin speaking.
Voice Recognition
Some sound cards are capable of voice recognition. You can
also get voice recognition for your current sound card in the
form of add-on software. Voice-recognition technology is
unfortunately still in its infancy, and you will need a fast
computer, such as a Pentium, for quick response times.
Voice Recognition is still sensitive to changes in a
person's voice, with both illness and stress changing a
person's voice enough to throw off most of the "consumer"
voice recognition products. Advances in this technology may
develop to a point where we'll be able to use continuous
speech to control our computer, rather than typing.
Proofreading
Sound cards can be used also as inexpensive proofreaders.
Text-to-speech utilities can read back to you a list of
numbers or text. This software is included with some sound
cards and can be used to read back highlighted words or even
an entire file.
This will allow you to more easily spot forgotten words or
awkward phrases when you hear a note read back to you.
Accountants can double-check numbers, and busy executives can
listen to their e-mail while they are doing paperwork.
Audio CDs
One entertaining use of a CD-ROM drive is to play audio CDs
while you are working on something else. The music can be
piped not only through a pair of speakers but also through a
headphone set plugged into the front of your CD-ROM drive.
Most sound cards include a CD-player utility, although free
versions are available on online services such as CompuServe.
These programs usually present a visual display similar to an
audio CD player. You operate the controls with a mouse or the
keyboard, and can listen to audio CDs while you work on other
things.
Sound Mixer
Any time you have multiple sources of sound that you want
to play through a single set of speakers, a mixer is
necessary. Most mixers are the kind that you see in music
videos, or in use by your local DJ.
Most sound cards have a built-in mixer to allow all of the
different audio sources, MIDI, WAV, Line IN, and the CD to be
played out of the single Line Out. Normally, software is
included with the sound card that displays visual sliders like
you would see on a standard mixer. This allows you to control
the relative volume of each of the sound sources.
Sound Card Concepts and Terms
To understand sound cards, you need to understand various
concepts and terms. Terms like 16-bit, CD
quality, and MIDI port are just a few. Concepts
such as sampling and digital-to-audio conversion
(DAC) are often sprinkled throughout stories about new
sound products. The following sections describe some common
sound card terms and concepts.
The Nature of Sound
To understand a sound card, you need to understand sound
itself. Every sound is produced by vibrations that compress
air or other substances. These sound waves travel in all
directions, expanding in balloon-like fashion from the source
of the sound. When these waves reach your ear, they cause
vibrations that you perceive as sound.
The two basic properties of any sound are its pitch and its
intensity.
Pitch is simply the rate at which vibrations are
produced. It is measured in the number of hertz (Hz),
or cycles per second. One cycle is a complete vibration back
and forth. The number of Hz is the frequency of the tone; the
higher the frequency, the higher the pitch. You cannot hear
all possible frequencies. Very few people can hear any fewer
than 16Hz or any more than about 20KHz (kilohertz; 1KHz equals
1,000Hz). In fact, the lowest note on a piano has a frequency
of 27Hz, the highest note, a little more than 4KHz. And
frequency-modulation (FM) radio stations broadcast notes up to
15KHz.
The intensity of a sound is called its amplitude.
This intensity depends upon the strength of the vibrations
producing the sound. A piano string, for example, vibrates
gently when the key is struck softly. The string swings back
and forth in a narrow arc, and the tone it sends out is soft.
If the key is struck forcefully, however, the string swings
back and forth in a wider arc. The loudness of sounds is
measured in decibels (db). The rustle of leaves is
rated at 20db, average street noise at 70db, and nearby
thunder at 120db.
Game Standards
Most sound cards support both of the current entertainment
audio standards: AdLib and Sound Blaster. The Sound
Blaster is a family of sound cards sold by Creative Labs;
AdLib sells their own cards as well. To play most
games, you must tell your game which of these sound card
standards your sound card supports. Sticking with a popular
sound card product (like the Sound Blaster line from Creative
Labs) will ensure that you always have software support. Most
software supports the Sound Blaster or AdLib cards, and
because of this, now most other brands' sound cards will
emulate one of these popular ones. If you have some
off-the-wall brand sound card and it does not emulate either
the Sound Blaster or AdLib cards, then you may find many
software products that do not specifically support your card.
NOTE: More and more games are being developed
for Windows 95. Games that are written for Windows 95 do not
require specific compatibility with any sound card. They
will work even if your sound card is not Sound Blaster- or
AdLib-compatible.
Frequency Response
The quality of a sound card is often measured by two
criteria: frequency response (or range) and total harmonic
distortion.
The frequency response of a sound card is the range
in which an audio system can record or play at a constant and
audible amplitude level. Many cards support 30Hz to 20KHz. The
wider the spread, the better the sound card.
The total harmonic distortion measures a sound
card's linearity, the straightness of a frequency
response curve. In layman's terms, the harmonic distortion is
a measure of accurate sound reproduction. Any nonlinear
elements cause distortion in the form of harmonics. The
smaller the percentage of distortion, the better.
Sampling
With a sound card, a PC can record Waveform audio.
Waveform audio (also known as sampled or
digitized sound) uses the PC as a tape recorder. Small
computer chips built into a sound card, called
analog-to-digital converters (ADCs), convert analog
sound waves into digital bits the computer can understand.
Likewise, digital-to-analog converters (DACs) convert
the recorded sounds to something audible.
Sampling is the process of turning the original
analog sound waves (see Figure 12.2) into digital (on/off)
signals that can be saved and later replayed. Snapshots of the
analog sounds are taken and saved. For example, at time X the
sound may be measured with an amplitude of Y. The higher (or
more frequent) the sample rate, the more accurate the digital
sound is to its real-life source.
FIG.
12.2 Sampling turns a changing sound
wave into measurable digital values.
8-Bit versus 16-Bit
The original MPC specifications required 8-bit sound. This
doesn't mean the sound card must fit into an 8-bit instead of
a 16-bit expansion slot. Rather, 8-bit audio means that
the sound card uses 8 bits to digitize each sound sample. This
translates into 256 possible digital values to which the
sample can be pegged (less quality than the 65,536 values
possible with a 16-bit sound card). Generally , 8-bit audio is
adequate for recorded speech, whereas 16-bit sound is best for
the demands of music. Figure 12.3 shows the difference between
8- and 16-bit sound.
FIG.
12.3 16-bit resolution allows more
accurate sound reproduction than 8-bit resolution.
Many of the older sound cards did 8-bit sound reproduction
only. Today, I would not recommend anything less than a 16-bit
card, which offers very high resolution.
Besides resolution, the sampling rate or frequency
determines how often the sound card measures the level of the
sound being recorded or played back. Basically, you have to
sample at about two times the highest frequency you want to
produce, plus an extra 10 percent to keep out unwanted
signals. Humans can hear up to 20,000 cycles per second, or
20KHz. If you double this number and add 10 percent, you get a
44.1KHz sampling rate, the same sampling rate used by
high-fidelity audio CDs.
Sound recorded at 11KHz (capturing 11,000 samples per
second) is fuzzier than sound sampled at 22KHz. A sound
sampled in 16-bit stereo (two channel) at 44KHz (CD-audio
quality) requires as much as 10.5M per minute of disk space!
The same sound sample in 8-bit mono (single channel) at 11KHz
takes 1/16th the space. If you were to add a one-minute hi-fi
voice annotation to your spreadsheet, you'd find a spreadsheet
whose size had increased by more than 10M.
The CD-ROM Connection
In addition to a sound card, the other foundation of
multimedia is a CD-ROM (compact disk read-only memory)
drive.
CD-ROM drives provide access to a wealth of text,
graphics, sound, video, and animation. Like a sound card, a
CD-ROM drive is essential for any multimedia PC.
Many sound cards double as a CD-ROM controller, or
interface, card. Some sound cards, however, use a proprietary
connection that accommodates only certain proprietary
interface CD-ROM drives. For a wider selection of drives,
consider a sound card that includes an IDE (Integrated Drive
Electronics) or SCSI-2 (Small Computer Systems Interface-2)
connector. If you are also going to attach other SCSI devices
such as hard disks, tape drives, or scanners, then I recommend
staying with a separate stand-alone SCSI-2 adapter. The
software driver support and performance will be much better
than on the Sound/SCSI combo cards.
For more information on CD-ROM drives, see Chapter 17
"CD-ROM Drives."
Sound File Formats
There are several file formats for storing and editing
digitized sound. The most notable is the WAV format
supported by Windows. (WAV is short for waveform
audio.) One audio minute saved to a WAV file requires 2.5M
to 10M or more of disk space, depending on the recording
options you select. Windows 95 offers recordings at several
different rates and bit depths.
Sound Reproduction
As mentioned previously, there are two methods for sound
reproduction. The older, cheaper, and less desirable method
called Frequency Modulation is losing favor as people move to
wavetable sound. When looking for a card today, look for
wavetable-based sound.
Compression/Decompression
Because one minute of stereo audio can consume up to 11M of
disk space, several sound card makers use Adaptive
Differential Pulse Code Modulation (ADPCM) compression to
reduce file size by more than 50 percent. However, a simple
fact of audio life is that when you use such compression, you
lose sound quality.
Because the sound quality can be degraded, there is no
ADPCM standard. Creative Labs uses a proprietary hardware
approach, while Microsoft is pushing the Business Audio ADPCM
design developed with Compaq.
The most popular compression standard is the Motion
Pictures Experts Group (MPEG) standard, which works with
both audio and video compression and is gaining support in the
non-PC world from products like the Philips CD-I player. MPEG
sports a potential compression ratio of 12:1, and due to this,
several full-motion-video MPEG CD-ROM titles are now
available.
Sound Card Characteristics
What are some key features to consider in a sound card?
Although some aspects are subjective, the following sections
describe some key buying points.
Compatibility
Although there are no official sound card standards, the
popular Sound Blaster card has become a de facto standard. The
Sound Blaster--the first widely distributed sound card--is
supported by the greatest number of software programs. A sound
card advertised as Sound Blaster-compatible should run
virtually any application that supports sound. Many sound
cards also support the MPC Level 2 or Level 3 specifications,
allowing you to play sound files in Windows and more. Some
sound cards, by excluding a MIDI interface, barely fall short
of the MPC specs. Other compatibility standards to look for
are AdLib and Pro AudioSpectrum.
CAUTION: Beware of sound cards that require
special drivers to be Sound Blaster-compatible. These
drivers can cause problems and will take up additional
memory that otherwise would be available.
Sampling
The most important sound card quality is its sampling
capability. The rate at which the card samples (measured in
KHz) and the size of its sample (expressed in bits) determine
the quality of the sound. The standard sampling rates for
sound cards are 11.025KHz, 22.050KHz, and 44.1KHz; sample
sizes are 8, 12, and 16 bits.
Inexpensive monophonic cards generally sample at 8 bits up
to speeds of 22.050KHz, which is fine for recording voice
messages. Some stereo-capable cards sample at 8 bits and run
at speeds of 22.050KHz in stereo and up to 44.1KHz in mono.
Other cards can sample 8 bits at 44.1KHz speeds in both stereo
and mono. The latest generation of cards do it all; they can
record CD-quality audio of 16 bits at 44.1KHz.
If you do buy a card that supports 16-bit sampling and plan
on doing any recording, make sure you have plenty of hard disk
space. The higher the resolution of sampling, the more hard
disk space needed to store the file. The sampling rate also
affects file size; sampling at the next higher rate doubles
the file size.
Stereo versus Mono
You'll also have to consider buying a monophonic or
stereophonic sound card. Inexpensive sound cards are
monophonic, producing sound from a single source.
Still, monophonic cards produce better sound than your PC's
speaker.
Stereophonic cards produce many voices, or sounds,
concurrently and from two different sources. The more voices a
card has, the higher the sound fidelity. Each stereo chip in a
sound card is capable of 11 or more voices. To get 20 or more
voices, manufacturers had to resort to two FM synthesizer
chips. Today, a single chip produces 20 voices, providing
truer stereo sound.
The number of voices a stereo card has is especially
important for music files because the voices correspond to the
individual instruments the card can play.
Most cheaper sound cards use FM synthesis to imitate the
musical instruments played. Most use synthesizer chips
developed by Yamaha. The least expensive sound cards use the
monophonic 11-voice YM3812 or OPL2 chip. Better sound cards
use the stereophonic 20-voice YMF262 or OPL3 chip.
Imitated musical instruments are not as impressive as the
real thing. Wavetable sound cards often use digital recordings
of real instruments and sound effects. Often, several
megabytes of these sound clips are embedded in ROM chips on
the card. For example, some sound cards use the Ensoniq chip
set (a type of circuit design) that does wavetable synthesis
of musical instruments. Instead of pretending to play a
trombone D flat, the Ensoniq chip set has a little digitized
recording of an actual instrument playing that note.
If your primary interest in a sound card is for
entertainment or for use in educational or business settings,
FM synthesis quality may be good enough.
Stereo sound cards vary in sampling rates and sizes. Some
stereo cards do not work in mono mode. Also, moving from mono
to stereo sound means an increase in the size of the sound
files. As with 16-bit resolution, stereo sound is not
supported by most software applications. However, a stereo
card playing mono software does generate better sound than a
mono card.
Another consideration when buying the more expensive stereo
cards is that they generally come with additional interfaces,
such as connections to a SCSI device (such as a CD-ROM drive)
or a MIDI device (such as a keyboard). In most cases, you will
get better performance from a CD-ROM drive by connecting it to
a motherboard IDE port or a separate high-performance SCSI
host adapter.
CD-ROM Connector
Most stereo sound cards not only provide great sound but
also can operate your CD-ROM drive. Although many cards come
with a SCSI port for any SCSI device, such as a CD-ROM drive,
others support only a proprietary CD-ROM interface, such as
Mitsumi or Sony CD-ROM interfaces. If you own a CD-ROM drive,
make sure it's compatible with the sound card you plan to buy.
If you plan to add a CD-ROM drive or expect to upgrade your
drive, keep in mind that a proprietary interface will limit
your choices, perhaps to a single CD-ROM brand.
If you're seeking to add both a sound card and a CD-ROM
drive, consider multimedia upgrade kits. These kits bundle a
sound card, CD-ROM drive, CD-ROM titles, software, and cables
in an attractively priced package. By buying a multimedia
upgrade kit rather than disparate components, you may save
some money. And you'll know that the components will work
together, especially if the kit includes proper documentation.
Data Compression
Most sound cards today can easily produce CD-quality audio,
which is sampled at 44.1KHz. At this rate, recorded files
(even of your own voice) can consume as many as 11M for every
minute of recording. To counter this demand for disk space,
many sound cards include a data-compression capability. For
example, the Sound Blaster ASP 16 includes on-the-fly
compression of sound in ratios of 2:1, 3:1, or 4:1.
MIDI Interface
The Musical Instrument Digital Interface (MIDI) is a
standard for connecting musical instruments to PCs. Many
stereo cards come with MIDI, synthesizer, and sequencing
software for composing music. Some cards include only a MIDI
interface; you have to purchase the hardware separately to
hook up other MIDI devices. Other sound cards may exclude the
MIDI.
MIDI allows your computer to store, edit, and play back
music through a MIDI instrument such as a keyboard
synthesizer. MIDI is more like a networking programming
language, allowing you to add more instruments, including drum
machines and special sound effects generators.
Bundled Software
Sound cards usually include several sound utilities so that
you can begin using your sound card right away. Most of this
software is DOS-based, but Windows-based versions are
available with some cards. The possibilities include:
- Text-to-speech conversion programs
- Programs for playing, editing, and recording audio
files
- Sequencer software, which helps you compose music
(generally included with cards with MIDI)
- Various sound clips
Multi-Purpose Digital Signal
Processors
One recent addition to many sound boards is the digital
signal processor (DSP). DSPs add intelligence to your
sound card, freeing your computer from work-intensive tasks,
such as filtering noise from recordings or compressing audio
on-the-fly.
About half of most general-purpose sound cards use DSPs.
The Cardinal Technologies Sound Pro 16 and Sound Pro 16 Plus,
for example, use the Analog Devices ADSP2115 digital signal
processor. The Sound Blaster AWE32's programmable DSP features
compression algorithms for processing text-to-speech data and
enables the card's QSound surround-sound 3-D audio, along with
reverb and chorus effects. DSPs allow a sound card to be a
multi-purpose device. IBM uses its DSP to add a 14.4Kbit/sec
modem, 9.6Kbps fax, and a digital answering machine to its
WindSurfer Communications Adapter.
Are DSPs worth the extra price? On low-powered PCs (those
less powerful than a 486SX/25) or in true multitasking
environments like Windows 95, Windows NT, or OS/2 Warp, a DSP
can make real-time compression possible--a feature valuable
for voice annotation. Note that many cards can be purchased
without the DSP chip and can have it added later as an
upgrade.
Sound Drivers
Most sound cards include universal drivers for DOS and
Windows applications. Find out what drivers are included with
your card. Windows 95 already includes drivers for the most
popular sound cards, such as Sound Blaster. Other drivers are
available on a separate driver disk available from Microsoft
or from Microsoft's Product Support download service.
Connectors
Most sound cards have the same connectors. These 1/8-inch
minijack connectors provide ways to pass sound from the sound
card to speakers, headphones, and stereo systems and to
receive sound from a microphone, CD player, tape player, or
stereo. The four types of connectors your sound card typically
could or should have are shown in Figure 12.4:
FIG.
12.4 The basic features most sound cards
have in common.
- Stereo line, or audio, out connector. The line
out is used to send sound signals from the sound card to a
device outside the computer. The cables from the line out
connector can be hooked up to stereo speakers, a headphone
set, or your stereo system. If you hook up your stereo
system, you can have amplified sound. Some sound cards, such
as the Microsoft Windows Sound System, provide two jacks for
line out. One is for the left channel of the stereo signal;
the other is for the right channel.
- Stereo line, or audio, in connector. The line in
connector is used to record, or mix, sound signals to the
computer's hard disk.
- Speaker/headphone connector. The
speaker/headphone connector is not always provided on a
sound card. Instead, the line out (described earlier)
doubles as a way to send stereo signals from the sound card
to your stereo system or speakers. When both
speaker/headphone and line out connectors are provided, the
speaker/headphone connector provides an amplified signal
that can power your headphones or small bookshelf speakers.
Most sound cards can provide up to 4 watts of power to drive
your speakers. Conversely, signals sent through the line out
connector are not amplified. Using the line out connector
provides the best sound reproduction because the stereo
system or amplified speakers will amplify the
sounds.
- Notice that most sound cards have a special pin type
connector that plugs directly into an internal CD-ROM drive
to allow sound to be played from the drive through the
speakers attached to the sound card.
- Microphone, or mono, in connector. You connect a
microphone to this 1/8-inch minijack to record your voice or
other sounds to disk. This microphone jack records in mono,
not in stereo. Many sound cards use Automatic Gain
Control (AGC) to improve recordings. This feature
adjusts the recording levels on-the-fly. A 600 to 10K ohm
dynamic or condenser microphone works best with this jack.
Some inexpensive sound cards use the line in connector
instead of a separate microphone jack.
- Joystick/MIDI connector. The joystick connector
is a 15-pin, D-shaped connector. Two of the pins are used to
control a MIDI device, such as a keyboard. Many sound card
makers offer an optional MIDI connector.
Sometimes the joystick port can accommodate two joysticks
if you order the optional Y-adapter. To use this connector as
MIDI, you'll need to buy the optional MIDI cable. Some sound
cards do not provide MIDI. If you're not interested in making
music (and spending a few hundred dollars more for the MIDI
keyboard), you may want to consider these models. And don't
worry about the lack of a joystick port. These are already
found in some PCs as a part of a Multi-I/O card; otherwise,
you can buy a separate stand-alone game card.
Volume Control
A thumbwheel volume control is provided on some sound
cards, although sophisticated sound cards have no room for
such a control. Instead, a combination of keys or a visual
slider control can be used to adjust the sound. By pressing
these key combinations, you adjust the volume from within a
game, Windows program, or any other application.
Sound Card Options
You'll seldom buy just a sound card. You'll need--or
want--other accessories that raise the cost of your PC sound
system. At the very least, you'll have to invest in a set of
speakers or headphones. At most, you may want to purchase a
MIDI synthesizer keyboard.
Speakers
Successful business presentations, multimedia applications,
and MIDI work demand external high-fidelity stereo speakers.
Although you can use standard stereo speakers, they are too
big to fit on or near your desk. Smaller bookshelf speakers
are better.
Sound cards offer little or no power to drive external
speakers. Although some sound cards have small 4-watt
amplifiers, they are not powerful enough to drive quality
speakers. Also, conventional speakers sitting near your
display may create magnetic interference, which can distort
colors and objects on-screen or jumble the data recorded on
your nearby floppy disks.
To solve these problems, computer speakers need to be
small, efficient, and self-powered. Also, you need to provide
magnetic shielding, either in the form of added layers of
insulation in the speaker cabinet or by electronically
canceling out the magnetic distortion.
CAUTION: Although most computer speakers are
magnetically shielded, do not leave recorded tapes, watches,
personal credit cards, or floppy disks in front of the
speakers for long periods of time.
Quality sound depends on quality speakers. A 16-bit sound
card may provide better sound to computer speakers, but even
an 8-bit sound card sounds good from a good speaker.
Conversely, an inexpensive speaker makes both 8-bit and 16-bit
sound cards sound tinny.
The dozens of models on the market range from less
expensive minispeakers from Sony and Koss to larger
self-powered models from companies such as Bose. To evaluate
speakers, you need to know the lingo. Speakers are measured by
three criteria:
- Frequency response. A measurement of the range of
high and low sounds a speaker can reproduce. The ideal range
is from 20Hz to 20KHz, the range of human hearing. No
speaker system reproduces this range perfectly. In fact, few
people hear sounds above 18KHz. An exceptional speaker may
cover a range of 30Hz to 23,000KHz. Lesser models may cover
only 100Hz to 20,000Hz. Frequency response is the most
deceptive specification, because identically rated speakers
can sound completely different.
- Total Harmonic Distortion (THD). An expression of
the amount of distortion or noise created by amplifying the
signal. Simply put, distortion is the difference between the
sound sent to the speaker and the sound you hear. The amount
of distortion is measured in percentages. An acceptable
level of distortion is below .1 percent (one-tenth of 1
percent). For some CD-quality recording equipment, a common
standard is .05 percent. Some speakers have a distortion of
10 percent or more. Headphones often have a distortion of
about 2 percent or less.
- Watts. Usually stated as watts per
channel, the amount of amplification available to drive
the speakers. Check that the company means "per channel" (or
RMS) and not total power. Many sound cards have built-in
amplifiers, providing up to 8 watts per channel. (Most
provide 4 watts.) The wattage is not enough to provide rich
sound, however, which is why many speakers have built-in
amplifiers. With the flick of a switch or the press of a
button, such speakers amplify the signals they receive from
the sound card. If you do not want to amplify the sound, you
typically leave the speaker switch set to "direct." In most
cases, you'll want to amplify the signal.
Two or four C batteries are often used to power computer
speakers. Because these speakers require so much power, you
may want to invest in an AC adapter, although more-expensive
speakers include one. With an AC adapter, you won't have to
buy new batteries every few weeks. If your speakers didn't
come with an AC adapter, you can pick one up from your local
Radio Shack or hardware store. Be sure that the adapter you
purchase matches your speakers in voltage and polarity.
You can control your speakers in various ways, depending on
their complexity and cost. Typically, each speaker has a
volume knob, although some share one volume control. If one
speaker is farther away than the other, you may want to adjust
the volume accordingly. Many computer speakers include a
dynamic bass boost (DBB) switch. This button provides a
more powerful bass and clearer treble, regardless of the
volume setting. Other speakers have separate bass and treble
boost switches or a three-band equalizer to control low,
middle, and high frequencies. When you rely on your sound
card's power rather than your speaker's built-in amplifier,
the volume and dynamic bass boost controls have no effect.
Your speakers are at the mercy of the sound card's power.
A 1/8-inch stereo minijack connects from the sound card
output jack to one of the speakers. The signal is then split
and fed through a separate cable from the first speaker to the
second one.
Before purchasing a set of speakers, check that the cables
between the speakers are long enough for your computer setup.
For example, a tower case sitting alongside one's desk may
require longer speaker wires than a desktop computer.
Beware of speakers that have a tardy built-in "sleep"
feature. Such speakers, which save electricity by turning
themselves off when they are not in use, may have the annoying
habit of clipping the first part of a sound after a period of
inactivity.
Headphones are an option when you can't afford a premium
set of speakers. Headphones also provide privacy and allow you
to play your sound card as loud as you like.
Microphone
Some sound cards do not include a microphone. You'll need
one to record your voice to a WAV file. Selecting a microphone
is quite simple. You need one that has a 1/8-inch minijack to
plug into your sound card's microphone, or audio in, jack.
Most have an on/off switch.
Like speakers, microphones are measured by their frequency
range. This is not an important buying factor, however,
because the human voice has a limited range. If you are
recording only voices, consider an inexpensive microphone that
covers a limited range of frequencies. An expensive
microphone's recording capabilities extend to frequencies
outside the voice's range. Why pay for something you won't be
needing?
If you are recording music, invest in an expensive
microphone, although an 8-bit sound card can record music just
as well with an inexpensive microphone.
Your biggest decision is to select a microphone that suits
your recording style. If you work in a noisy office, you may
want a unidirectional microphone that will prevent extraneous
noises from being recorded. An omnidirectional mike is best
for recording a group conversation.
Most higher-priced sound cards include a microphone of some
type. This
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