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Re: [AUDITORY] Phase flip detection

It seems reasonable to me that a 180 degree reversal would be hard to detect across a gap or noise, but that other phase changes might be more detectable -- e.g. a time reversal.  The work of Patterson and colleagues on ramped vs damped sinusoids suggests that these periodic signals that differ only by time reversal (which is just a phase change) have distinguishable timbres.  I'd try something like that, or perhaps up vs. down chirplets.  But I have no knowledge of particularly relevant experiments.


On Mon, Jan 16, 2023 at 4:15 PM Bob Carlyon <Bob.Carlyon@xxxxxxxxxxxxxxxxx> wrote:

Dear Robert,


Yes, we did something quite similar both with Fam and AM applied to pure tones. Listeners are very good at detecting a physical reversal in the ongoing FM or AM phase, but for the case of the noise interruption, which evokes the continuity illusion, these changes are not detectable.

Our original findings with FM phase are here:

R.P. Carlyon, C. Micheyl, J.M. Deeks, and B.C.J. Moore (2004). Auditory processing of real and illusory changes in FM phase”. J. Acoust. Soc. Am. 116, 3629-3639.


And were subsequently expanded to encode AM phase:

J. Lyzenga, R.P. Carlyon, and B.C.J. Moore (2005). Dynamic aspects of the continuity illusion: perception of level and of the depth, rate, and phase of modulation”. Hearing Research, 210, 30-41.


We concluded that the brain explicitly encodes and retains the presence and depth of FM but not its phase. There is an analogy I think with the Shailer & Moore article that Skyler cited in reply to your query, which uses interrupted pure tones. In that case listeners are sensitive to the “preserved phase” only when the gap is short enough for there to be an interaction at the level of the basilar membrane, but no one would expect listeners to detect differences in the starting phase of two pure toes separated by say 500 ms. That is presumably because the brain does some analysis o extract the frequency and level of the tone, the reults of that analysis can be remembered, but the analysis does not explicitly encode phase.


Best wishes,





From: AUDITORY - Research in Auditory Perception <AUDITORY@xxxxxxxxxxxxxxx> On Behalf Of R. Zatorre, Dr.
Sent: 14 January 2023 23:17
To: AUDITORY@xxxxxxxxxxxxxxx
Subject: Phase flip detection



Dear colleagues


We are doing a study with a simple stimulus. It's a periodic complex tone which is interrupted briefly by a noise burst (noise starts and ends at a zero crossing, and there's a short ramp on either side). On half the trials the tone continues with the same phase as if no noise had occurred. In the other trials, the phase is flipped by 180 degrees. (See figure below)


Question: does anybody know of a previous experiment with a similar setup? Is the phase flip perceivable? Casual listening by a few of us in the lab suggests it is not, and we will do proper psychophysics to test this out. But we thought that perhaps to avoid re-inventing the wheel we should see if something like this has already been tried. There are dozens of papers out there on various aspects of phase perception, but most seem to deal with binaural hearing or manipulations of phase of the harmonics of a complex tone, neither of which are really relevant.


Thank you in advance for your collective wisdom.




without phase shift 



With phase shift:





Robert Zatorre, PhD

Professor and Canada Research Chair

Montreal Neurological Institute

McGill University
fax: 514-398-1338