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Frequency
introduction
In addition to amplitude, frequency is one of the fundamental aspects of sound. Amplitude is the strength of the air pressure waves, and frequency is how frequently those waves occur. It is the strongest factor in determining pitch.
One of the most fundamental facts about frequency to remember is that humans can hear 20-20000 Hz. Then you need develop familiarity with which types of sounds exist within which frequency range.
It is also important to remember that sounds do not exist as a single frequency but are constituted by a collection of frequencies.
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The difference between frequency and pitch: