Gold & Pumphrey (Experiment I)

[Andrew Bell <andrew.bell@xxxxxxxxxx>]

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@anu.edu.au
phone +61 2 6125 9634
fax +61 2 6125 3808
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

-----Original Message-----
From: AUDITORY Research in Auditory Perception
[mailto:AUDITORY@LISTS.MCGILL.CA]On Behalf Of Christopher Shera
Sent: Tuesday, 26 March 2002 1:25
To: AUDITORY@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.