ASA 26 - Scales With Repetition Pitch

Description

One way to demonstrate repetition pitch in a convincing way is to play scales or melodies using pairs of pulses with appropriate time delays between members of a pair.

In the first demonstration, a 5-octave diatonic scale is presented using pairs of identical pulses. In each pair the second pulse repeats the first, with a certain time delay, which changes from 15 ms to 0.48 ms as we proceed up the scale.

Next a 4-octave diatonic scale is presented using trains of pulse pairs that occur at random times. Time intervals between leading pulses have a Poisson distribution. Delay times tau between pulses of each pair vary from 15 to 0.85 ms. Although the pulses now appear at random times, a pitch corresponding to l/t is heard, as in the first demonstration.

The final demonstration is a 4-octave diatonic scale played with bursts of white noise that are echoed 15 ms to 0.85 ms later.

References

F.A.Bilsen (1966), "Repetition pitch: monaural interaction of a sound with repetition of the same, but phase shifted sound", Acustica 17, 295-300.

Frequency

		Time Delay

Transcript

First you will hear a 5-octave diatonic scale played with pulse pairs.

Frequency

		Time Delay

Transcript

Now you hear a 4-octave diatonic scale played with pulse pairs that are samples of a Poisson process.

Frequency

		Time Delay

Transcript

Finally you hear a 4-octave diatonic scale played with bursts of echoed or 'comb filtered' white noise.