Re: Request of paper "Implementing a gammatone filterbank" by Patterson et al. (Roy Patterson )

Subject: Re: Request of paper "Implementing a gammatone filterbank" by Patterson et al.
From:    Roy Patterson  <rdp1@xxxxxxxx>
Date:    Fri, 14 Nov 2008 11:03:45 -0800

Arturo Camacho wrote: > Dear members of the list: > > Can someone please facilitate me a copy of the paper "Implementing a > gammatone filterbank", APU Report 2341 by R. Patterson et al? I have > found in several papers/books a formula to compensate for the > differences in delay that exist in the different channels of a > gammatone filterbank, and they cite the aforementioned paper as the > origin of the formula. I would like to take a look at that paper to > learn more about the method. APU Report 2341 was written before the advent of electronic figures and pdf's. I guess I should scan the paper and put it on our web page, but I am in California at the moment so it will be closer to Christmas when that happens. The point the paper makes is as follows: The fluid in the cochlea is incompressible. So when the cochlea is hit by an impulse, all of the filters in the filterbank begin to respond at the same instant. However, the bandwidth of the auditory filter narrows as centre frequency decreases down the length of the cochlea. The impulse reponse in a narrow filter takes longer to rise to its maximum than it does for a broad filter. So the delay you see in a cochleogram is the delay in rise time of the filter due to the narrowing of filter bandwidth. Thus, the delay is the delay of the maximum of the gamma envelope of the filter which is easy to calculate. The only complication is that you do not actually see the envelope in the output of the filter, you see the peaks of the carrier, and these peaks shift a little relative to the peak of the envelope. But again it is easy to calculate where they will occur given the equation for the impulse response of the filter. Regards Roy P -- * ** *** * ** *** * ** *** * ** *** * ** *** * Roy D. Patterson Centre for the Neural Basis of Hearing Department of Physiology, Development and Neuroscience University of Cambridge Downing Street, Cambridge, CB2 3EG phone: +44 (1223) 333819 office fax: +44 (1223) 333840 department email rdp1@xxxxxxxx

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