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Temporal Coherence in the Perception of Tone Sequences
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Part 4:
Coherence and Fission through Amplitude Differences
Load example circuit for part 4
Temporal fission can also be caused by differences in loudness.
These examples will demonstrate that there is an amplitude threshold between
hearing the same note or two separate notes, even though they are the same frequency.
The threshold between coherence and fission also effects the perceived tempo.
To minimize the effects of room ambiance and reverberation,
this example is best heard with head-phones.
Start with tones A and B at the same frequency of 1000 Hz.
Have the circuit make the pattern ABAB.. with equally loud tones (maximum level)
Set the T slider to 0.1 sec, i.e. ten tones per second.
With identical amplitudes
you will hear a monotone sequence of ten tones per second, temporal coherence.
Lower the volume of tone A to zero and you will hear a sequence with half the tempo.
Slowly increase the volume of tone A until you
can hear both the weak tones and the loud tones as two separate sequences.
The perceived tempo will be five tones per second, even though there are really ten note per second.
This is temporal fission.
As you continue to raise the level of tone A it becomes increasingly more difficult to hear fission.
At about 1db of difference you will most probably hear the sequence of the double tempo,
although it is still possible to hear that there is a level difference between the tones.
Now there is temporal coherence in the tone sequence again.
You can also try the same the pattern ABA ABA.
Through the gallop rhythm you may recognize the temporal coherence better.
There is also a difference when tone A or tone B is the louder tone.
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