Recognizing pitch requires a tone of minimal duration. Regardless of frequency, durations of only a few milliseconds are heard as clicks. As the duration is lengthened the click develops a tonal quality that allows some listeners to discriminate among clicks on the basis of click pitch. The minimum period of time for a frequency to be perceived as pitch varies with frequency below 1000 Hz when two to three cycles are needed. Above 1000 Hz a minimum duration of 10 ms is required.

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To really understand why extremely short notes are perceived as containing all frequencies and are therefore perceived as clicks would require using Fourier analysis.

Wolfgang