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Correlations, but ...

Chuck Watson wrote -

"I would be curious to know ... whether there
is a correlation between, say, critical ratios, band-narrowing critical
bands, and notched-noise CB's.  Sounds like a 70's-era dissertation."

Work on this was actually done in the 70's and 80's. In our paper

Patterson, R.D., Nimmo-Smith, I., Weber, D.L., and Milroy, R. (1982).  The
deterioration of hearing with age:  Frequency selectivity, the critical
ratio, the audiogram, and speech threshold.  J. Acoust. Soc. Am., 72, 1788-1803.

there is a large correlation matrix (p1794) including the ERB parameter, p,
and the critical ratio, Ps(0). It also includes the efficiency constant K.
The table shows that p correlates highly with a number of parameters, but
not with Ps(0) and K. the high correlations associated with p arise from the
low standard deviation of the measure, which in turn arises from the
sensitivity of the notched-noise method. The low correlations with Ps(0) and
K arise because frequency selectivity and efficiency are confounded in the
Ps(0) measure, as we explain in the introduction to the paper.

The Critical Ratio is a particularly bad measure of auditory filter bandwidth!

With regard to Fletcher's band narrowing experiment, its disadvantages are
discussed at length in

Patterson, R.D. and Henning, G.B. (1977).  Stimulus variability and auditory
filter shape.  J. Acoust. Soc. Am., 62, 649-664.

Briefly, although the power-spectrum math for the band narrowing method and
the notched-noise method are very similar, it is important to understand
that the band narrowing version has two very serious weaknesses:
1) it confounds stimulus variability with filter shape, so you need full
detection theory stats for the band narrowing derivation and no one ever
uses them (Section III.C, Fig. 4).
2) the band narrowing version of the experiment is particularly insensitive
(Section IV), whereas the notched-noise method is highly sensitive.

Cheers Roy

Roy D. Patterson
Centre for the Neural Basis of Hearing
Physiology Department, University of Cambridge
Downing Street, Cambridge, CB2 3EG

phone   44 (1223) 333819        office
phone   44 (1223) 333837        lab
fax     44 (1223) 333840        department
email   roy.patterson@mrc-apu.cam.ac.uk


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