Psychoacoustics: the logarithmic perception of pitch
| The human ear is capable of hearing over wide range of sound pressure (loudness) and frequency. It seems that in order to maintain sensitivity where we need it most, our perception of sound, in the broadest sense, has evolved to be roughly logarithmic. The term pitch refers to our perception of musical sound. It is generally tied to the fundamental frequency or, that is to say, the longest wavelength associated with a given musical note. The grand piano has 88 keys with corresponding fundamental frequencies of approximately 28 Hz (A0) to 4200 Hz (C8). Consistent with our logarithmic sense of perception, we hear the doubling of a fundamental frequency as the same note, only higher in pitch. This doubling in frequency is referred to as an octave. The grand piano has a range of just over seven octaves. The sense of equivalence between notes that are an octave apart is effectively demonstrated through an aural illusion known as Shepard Tones in which a series of discreet tones appears to rise without end.
The continuous version of this illusion is called a Risset Scale.
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