Re: Rationale for Critical Bands

["Richard F. Lyon" <DickLyon@xxxxxxx>]

I checked some books, and come back to my original statement that the 
"critical bandwidth" is a simplification of the concept of a 
psychophysical "auditory filter".  The former typically ignores level 
dependence (or assumes level independence) and ignores shape, while 
the latter includes shape and the dependence of shape, and hence of 
bandwidth, on level.

I found a citation to this paper to support a statement that the CB 
is known to be level dependent:
@article{moore1987formulae,
  title={{Formulae describing frequency selectivity as a function of 
frequency and level, and their use in calculating excitation 
patterns}},
  author={Moore, B.C.J. and Glasberg, B.R.},
  journal={Hearing Research},
  volume={28},
  number={2-3},
  pages={209--225},
  year={1987},
  publisher={Elsevier}
}
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T73-485GKTP-J5&_user=10&_coverDate=12%2F31%2F1987&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1369699969&_rerunOrigin=scholar.google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=9fc7c66e164255fe5050defe0cd43f95

I don't have the paper; the abstract talks about level dependence of 
the filter, not of the bandwidth per se.  Probably that's in the 
paper, as these authors do commonly characterize their filter shapes 
with an equivalent rectangular bandwidth.

The support cited for CB being level independent, e.g. in some of the 
papers that Martin linked, was Ehret 1985, a bit earlier.  So 
probably this was the timeframe when the level dependence of a 
psychophysical CB was being recognized, via careful study of auditory 
filters.  In his 1997 book, Ehret says critical ratios are "less 
intensity-dependent in many, mainly higher-order neurons of the CN as 
compared to in the AN", citing his 1983 and 1984 papers.
http://books.google.com/books?id=2OG_iVgthNoC&pg=PA167&dq=%22critical+ratios%22+%22less+intensity-dependent%22&hl=en&ei=8MUWTPORBIbknQfEhrXGCg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCUQ6AEwAA#v=onepage&q=critical%20intensity&f=false
He probably says more later in the book about IC, but I can't see 
those pages.  Perhaps it's still the case that in IC the CB is level 
independent?  It would be very interesting if so.  It's not clear to 
me how measurement in IC (or CN or AN for that matter) relate to 
psychophysical measures; maybe someone can say?

Dick