Introduction to Computer Music: Volume One

5. What is frequency? | page 2

The range of human hearing in the young is approximately 20 Hz to 20 kHz—the higher number tends to decrease with age (as do many other things). It may be quite normal for a 60-year-old to hear a maximum of 16,000 Hz.

Amazing factoid #2: For comparison, it is believed that many whales and dolphins can create and perceive sounds in the 175 kHz range. Bats use slightly lower frequencies for their echo-location system.

Frequencies above and below the range of human hearing are also commonly used in computer music studios. We refer to these ranges as:

<20 Hz
20-20kHz
>20kHz
sub-audio rate
audio rate
ultrasonic

Sub-audio signals are used as controls (since we can't hear them) in synthesis to produce effects like vibrato. The lowest 32' organ pipes also produce fundamental frequencies below our ability to hear them (the lowest, C four octaves below "middle C," is 16.4 Hz) — we may sense the vibrations with our body or extrapolate the fundamental pitch from the higher audible frequencies (discussed below), but these super-low ranks are usually doubled with higher ranks that reinforce their partials.

 

 

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