Can changes in the ADSR envelope of a tone affect perceived fission?
By: Michael Anoke
The following illusion study built on the idea of sequential grouping with an ABA pattern as discussed with relation to temporal coherence, as well as using Attack, Decay, Sustain, Release (ADSR) to attempt to synthesize natural sounds. In the temporal coherence paper, they discuss how a large increase in tempo can cause the loss of temporal coherence and cause the perception of fission within the ABA-ABA pattern. Fission is expressed as the perception of the A's and B's in the pattern sounding as if they are from two separate sources/streams. This contrasts temporal coherence, in which a "galloping" sound would be heard, as the A's and B's would be perceived as a single stream. There is a tempo threshold in which someone can no longer hear temporal coherence, or they can no longer hear fission.
This illusion study looked at the tempo threshold, and examined how it varies with changes to an ADSR envelope. ADSR envelopes are typically used in the synthesis of more natural sounds, and I wanted to see whether changing one of the 4 parts of the envelope would move the tempo threshold. The tones are each one-tenth of a second, and the silence between the tone changes with each iteration of the sound effect. The sounds come from looking at the fast-fourier transform (fft) of two piano notes, and using the frequency information to try and recreate a similar tone.
van Noorden, L.P.A.S. (1975). Temporal coherence in the perception of tone sequences.
Wessel, D. (1979). Timbre Space as a Musical Control Structure. Computer Music Journal, 3(2), 45-52. doi:10.2307/3680283
Comments
Maria De La Torre
a) All of the sounds changed the fission threshold for me but each one at different magnitudes. The one that was most distinctive was "Changed Release" and "Changed Decay" for me, through which I perceived the sounds as one almost until the end of the sequence. The other two also changed the threshold much only by a few more repetitions than the control.
b) The experience of this illusion does answer the research question posed of whether different changes to the ADSR envelope could shift the threshold of sound grouping and all of the variations did show different shifts of this threshold. After reading the comments, I listened to the sounds varying my attention and I do agree that this makes a difference in the magnitude of the threshold-shift.
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Anonymous
@Elian
c) Your results partially answer my question by showing at least a change in one part of the ADSR envelope could change the fission/temporal coherence boundary.
d) I wonder if splitting the experiment into two parts might help answer my question better. For the first part, ask the participate to focus and how many repetitions they hear as separated. For the second part, the participants would be asked to pay attention and be asked how many repetitions they hear as together. Perhaps the comparison of the two answers could provide additional insight.
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Maddie
The first time I listened to each one, these are the results I got;
Control: last two repetition were segregated
Changed attack: last four were segregated
Changed decay: grouped through the whole sequence
Changed sustain: the last six were segregated
Changed release: grouped through the whole sequence
Seeing Elian's comment, I went through again and checked how variable the thresholds were and if I could get them to shift through attention. They did vary quite a bit, maybe +/- 2 reptitions
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Michael Anoke
@Maddie
c) Similar to Elian, the fact that for some changes to the ADSR envelope, a different number of repetitions were segregated for you, your results partially answer my question.
d) As a follow-up question, I wonder how perceivable the different envelopes would be if they were played binaurally.
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Elian Malkin
a) Change in decay noticeably lowered the fission threshold for me, while the threshold in others sounded very similar to the control.
b) Experiencing this demo helped answer whether modifying the ADSR envelope affects perceived fission - it suggested that specific components of the ADSR envelope could be changed to alter the threshold of transition from temporal coherence to fission. It is fairly difficult to precisely evaluate one's threshold as the boundary between temporal coherence and fission seems somewhat fuzzy and attention-dependent.
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Anonymous
a) Change in decay noticeably lowered the fission threshold for me, while the threshold in others sounded very similar to the control.
b) Experiencing this demo helped answer whether modifying the ADSR envelope affects perceived fission - it suggested that specific components of the ADSR envelope could be changed to alter the threshold of transition from temporal coherence to fission. It is fairly difficult to precisely evaluate one's threshold as the boundary between temporal coherence and fission seems somewhat fuzzy and attention-dependent.
