Subject: Re: Is there considerable phase locking up to 6 kHz? From: "Richard F. Lyon" <DickLyon(at)ACM.ORG> Date: Tue, 16 Mar 2004 17:49:52 -0800Now that I've read Eckard Blumschein's note about how maybe "Pitch apparently relates to a kind of autocorrelation that is not based on phase locking," I think I need to clarify Jan Schnupp's answer in relation to Hi Cheng-Gia's question. It is fair to say that "most auditory physiologists would be very surprised if any mammal was found to phase lock appreciably to frequencies above 4 kHz." But this should NOT be interpreted to mean that auditory neurons with a CF above 4 kHz will not show accurate synchrony to high-frequency complexes with a lower pitch. No phase locking to frequencies above 4 kHz should be re-phrased as no phase locking to sine waves above 4 kHz. The original question noted that autocorrelation type mechanisms could work for the "complex tones with unresolved odd-numbered harmonics", "...if temporal cues for pitch extraction were assumed to be maintained in the range of 4 - 6 kHz." It should be noted that even were the components resolved, there would be regions of the cochlea responding with strong modulation to the beat envelopes, and a pitch near the difference frequency would be expencted. Furthermore, it doesn't take much synchrony to the fine-scale structure of the 4-6 kHz components to induce autocorrelation peaks shifted slightly from the envelope frequency. Do we have good experimental data on the degree of synchrony to such complexes? Probably so, but it's been a long time since I looked. Similar questions come up in binaural laterization by cross-correlation. It is impossible to localize sinusoids around 4 to 6 kHz, but if I recall correctly, complexes with enough temporal structure in that frequency band can be localized quite well, corresponding to time errors well under a cycle. It seems to me that if we can localize such sounds, then there must be enough synchrony there to use for pitch extraction as well. Dick At 11:34 AM +0000 03/16/2004, jan schnupp wrote: >chen-gia tsai wrote: > >>Dear all, >> >>I am working on the pitch perception of music sounds with dominant >>upper odd-numbered harmonics. >> >> >... snip... > >>This finding prompts the question: is there considerable phase >>locking up to 6 kHz? >> >> >Hi Cheng-Gia, >to the best of my knowledge, the answer to your prompted question is >that, unless you are a barn owl (who may phase lock up to 9 kHz), >the answer is almost certainly no. Auditory nerve recordings in cat >and guinea pig have shown rather similar roll-offs in phase locking, >starting at about 2 kHz or so (the curve rolls off earlier in guinea >pigs) and by 4kHz there is practically no phase locking left. I >don't know of any data from human auditory nerve fibres (for obvious >reasons, such data would be hard to come by) but I think most >auditory physiologists would be very surprised if any mammal was >found to phase lock appreciably to frequencies above 4 kHz. >Non-mammals typically do much worse than mammals. In this respect >(as in many others) barn owls seem to be extremely unusual, and they >should perhaps be reclassified as aliens from outer space. >When you mention that your stimuli lead to a perception of a rising >"melody", you may have to tread a little carefully. When you say, >"the musical pitch is ambiguous", some might argue that "ambiguous" >means there no longer is "pitch" in the strict sense, and hence >there is no longer "true melody". This isn't really my field of >expertise, but I believe that frequency discrimination limens get >much larger for frequencies above 4 kHz. If listeners can no longer >easily discriminate a semitone, are we still looking at pitch >phenomena? > >Regards, > >Jan > >-------------------------------------------------------- >Dr. Jan Schnupp >University Laboratory of Physiology St Peter's College >Oxford University New Inn Hall Street >Parks Road, Oxford OX1 3PT, UK Oxford OX1 2PL >Tel (01865) 272513 Tel (01865) 278889 >Fax (01865) 272469