Subject: Gold & Pumphrey (Experiment I) From: Andrew Bell <andrew.bell(at)ANU.EDU.AU> Date: Fri, 17 May 2002 15:37:38 +1000
Christopher Shera pointed out that Experiment II of Gold & Pumphrey (1948) is not a conclusive demonstration of high Q in the ear. He noted that, potentially, the listeners had available other spectral cues that may have caused a perceptual difference between a sequence of in-phase pulsed tones and its counterpart comprised of pulsed tones alternating in phase. Revisiting this paper, I note that no-one has commented on Gold and Pumphrey's Experiment I, another experiment which set out to demonstrate that the ear has high Q. The experiment involved measuring the difference in perceptual threshold between a pure tone of a given frequency and that for an abbreviated version of it consisting of a limited number of cycles. The trade-off between number of cycles and audibility will simply depend on the Q of the resonator being excited. Because the subject always needed to detect only the strongest spectral peak, any sidebands of the pulses will fall below the threshold of audibility, allowing us to treat the above-threshold activity as simple harmonic oscillation at the sine-tone frequency. The proviso, pointed out by G&P, is that the threshold for nearby frequencies is not appreciably different to the frequency under consideration, a condition that rules out use of low-frequency tones. Gold and Pumphrey's results are in line with their theoretical analysis, and are consistent with a Q of the ear of 80--300 at 2 kHz and above. Can the conclusion of Experiment I be disputed? Andrew. [ref: Gold & Pumphrey: Proc. Roy. Soc. B 135 (1948), 462-491] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Andrew Bell Research School of Biological Sciences Institute of Advanced Studies Australian National University Canberra, ACT 0200, Australia andrew.bell(at)anu.edu.au phone +61 2 6125 9634 fax +61 2 6125 3808 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -----Original Message----- From: AUDITORY Research in Auditory Perception [mailto:AUDITORY(at)LISTS.MCGILL.CA]On Behalf Of Christopher Shera Sent: Tuesday, 26 March 2002 1:25 To: AUDITORY(at)LISTS.MCGILL.CA Subject: Re: Gold & Pumphrey Christopher Shera wrote: >The point missed here (and the point missed by G&P) is that >G&P's analysis--and hence their derived numerical values of Q---only >applies if the frequency analyzer in question is a single harmonic >oscillator (2nd-order resonator) tuned to the sine-tone frequency. >Of course, the ear (even the cochlear part) is more complicated than >that. For a nice discussion see Hartmann's "Signals, Sound, and >Sensation." pg. 310ff. in reply to Andrew Bell who wrote: >>Pumphrey and Gold would not dispute that there is a (spectral) >>difference between the two wavetrains A and B. Indeed, if there >>were absolutely no difference, then no frequency analyser on earth >>would be able to tell the difference between them. What Pumphrey and >>Gold are simply saying is that any difference between A and B can only >>be perceived if the analyser has a sufficiently high Q.