Computer Sound Synthesis II

Sound Waves. Sounds travels in the form of air pressure waves. Microphones transform them into analog variations of electric current. These variations travel through the wires to speakers where they make the cone vibrate and set the air in motion, producing again air pressure waves. The range of the human aural perception is roughly 20 - 20,000 Hz (cycles /sec or such variations per second).

For all this and the following topics consult

John Pierce and Max Mathews - The Science of Musical Sound

on reserve

Sampling. The variations of the electric current are in the form of a wave which can be measured from time to time. These measurements or samples are done with a device called Analog to Digital C onverter (ADC). In order to obtain adequate measurements which will catch all present frequencies, the number of samples per second should be at least twice the number representing the highest frequency. The recording standard is 44,100 samples/sec and the broadcasting standard is 48,000 samples/sec. These samples (numbers) can be stored in a computer's memory and used to produce a CD. When you listen to your CD, such samples (numbers) are read by a Digital to Analog Converter (DAC). A composer can either process further these numbers (samples) or create them from scratch with the aid of known algorithms.

Sound Synthesis Methods.
In class we briefly mentioned a few methods or systems used in digital sound synthesis:

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