An introduction to sampling

Sampling is conceptually simple; an incoming analog sound signal is
converted to a digital number (0-255 on the IIgs). Getting good
samples depends on a number of factors:

* Sampling rate. This is how often in samples per second the
incoming signal is actually noticed and saved. In general, you
want to have a sampling rate of twice the frequency of the highest
pitch sound you intend to sample. (The reasoning behind this is
known as the Nyquist Sampling Theorem). Compact discs sample at
44,100 Hz, which means they can accurately track signals up to
22,050 Hz, beyond the range of human hearing. Long-distance
telephone calls are sampled at 8,000 Hz, since the characteristic
part of human voices is generally from 1000-3000 Hz. If
frequencies higher than or equal to half your sampling rate exist,
they will manifest as distortion in the output sample.
* Stereo card quality and shielding (the Audio Animator makes the
best samples of any card I've tried, by far).
* Input signal level (the higher the better, except that there is a
threshold known as the 'clipping level' above which the sampler
will be unable to track the signal. Analog tape recorders do
something very similar).

Once a sample is made, it can be manipulated in a variety of ways via
mathematics. Because this processing is digital, no degradation of the
signal can occur, unlike with analog processing. Some effects which
can be done include:

* Cut and pasting parts of the sample around.
* Mixing/overlaying two samples.
* Flanger/Chorus effects.
* Amplification and deamplification.
* Echoing
* Filtering and equilization

and much more...check out a modern rack-mounted guitar digital signal
processor for all the things possible :)

To digitize a sound (I'll use AudioZap as the example, others are
similar):

* Hook everything up.
* Check the oscilloscope. The wave should be barely touching the top
and bottom of the 'scope. Any higher and the sound is clipping;
any lower and you'll get a poor quality recording. Adjustment
methods vary by card; for the Sonic Blaster card AZ can adjust it
in software. Otherwise, consult your card's manual.
* Select a recording rate (lower numbers on AZ = faster).
* Click Record and cue up your tape or CD.
* Select Ok and then start the tape or CD.
* Click the mouse and stop the tape or CD when you are done.

You've just made a sample! congratulations! Experiment...you can't
hurt anything, but may discover fun/neat things to do!

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