Analog Box 2 : Audio Research : Temporal Coherence : Part 3.2-5

Temporal Coherence in the Perception of Tone Sequences

Part 3.2
Pitch or Spectral Components

This example circuit has four states, each of which illustrates a combination of pitch and frequency components. The two buttons at the bottom left of the circuit allow you to choose the state.

state 1

In a fast sequence of two complex tones with the same pitch but with non-contiguous frequency components, we hear fission and not temporal coherence.

state 2

But temporal coherence is heard when the tones are contiguous in pitch and in components. Temporal coherence is inevitable.

state 3

We now change the pitch of the odd tones by an octave; At the tone repetition time of 100 ms the situation is not very clear. It is possible that you can pick out the slow tone sequence with the lower pitch. But it is also possible to hear the gallop rhythm. In faster sequences it seems more difficult to hear fission.

state 4

If we also make the tones non-contiguous in spectral components we hear fission, no temporal coherence can be heard.

From the above demonstrations it follows that the contiguity of spectral components important for hearing temporal coherence. A difference in pitch can be heard as fission, but is on its own not sufficient to hear temporal coherence.