Re: AUDITORY Digest - 31 Mar 2006 to 1 Apr 2006 (#2006-75) (Jont Allen )

Subject: Re: AUDITORY Digest - 31 Mar 2006 to 1 Apr 2006 (#2006-75)
From:    Jont Allen  <jontalle@xxxxxxxx>
Date:    Sun, 2 Apr 2006 05:18:28 -0500

Niky
The way that humans are believed to do this pure tone pitch 
discrimination, is via an amplitude change off of the very steep 
cochlear filter. The skirt is more than 100 dB/oct, so a small change in 
freq leads to a channel output having a large amplitude change. It's 
easy to get the numbers in DF -> DI.

However, speech and music are not pure tones, they are tone complexes, 
and the pitch of these complex sounds is not the same as that of a pure 
tone. The pitch you hear in a speech sound it the "residue pitch" not 
the pure tone pitch. This was figured out by 1924

@xxxxxxxx{Fletcher24d,
author={Fletcher, Harvey},
title={Some further experiments of the pitch of musical tones},
journal=PHYREV,
year={1924},
month=jan,
volume={23},
pages={117--118},
note_={} }

@xxxxxxxx{Fletcher24c,
author={Fletcher, Harvey},
title={The physical criterion for determining the pitch of a musical tone},
journal=PHYREV,
year={1924},
month=mar,
volume={23},
number={3},
pages={427--437},
note_={} }

For some history look at

@xxxxxxxx{Pierce95
,author={Pierce, J.R.}
,title={Fletcher's discoveries concerning pitch}
,journal=JASA
,year=1995
,month=dec
,volume={98}
,number={6}
,pages={3019--3020}
,note={} }

Finally, there is lots of modern material on this subject, so get a good 
book, and read about it. I'ts not a small topic, and there {may | seem 
to} be differing opnions floating around.

Start with

@xxxxxxxx{Hartmann97
,author={Hartmann, William M.}
,title={Signals, Sound, and Sensation}
,year={1997}
,publisher={AIP Press}
,address={American Institute of Physics, Woodbury, NY}
,note_={}
          }

Jont


AUDITORY automatic digest system wrote:
> There are 2 messages totalling 122 lines in this issue.
> 
> Topics of the day:
> 
>   2. semitone spacing in cochlear implants?
> 
> ----------------------------------------------------------------------
> 
> Date:    Sat, 1 Apr 2006 16:53:40 +0100
> From:    niky prabhu <niky_prabhu@xxxxxxxx>
> Subject: <No subject given>
> 
> --0-391797179-1143906820=:3244
> Content-Type: text/plain; charset=iso-8859-1
> Content-Transfer-Encoding: 8bit
> 
> Dear members
>    
>   I am working on the effects of filter spacing on melody recognition as an implication for cochlear implants. I have considered 4 filter spacings (i.e the Mel, ERB, Linear and the Semitone scales) to space 8 AM channels in an overall processing band from 80-4000Hz - for piano played melodies. 
>    
>   The problem that was faced was in spacing the semitone tone scale. 
>    
>   - if i consider a band width of around 2-3 semitones, i would cover only a small range of the entire band from 80-4000Hz. and inorder to cover the entire range i require many sets of filters spaced with the same width. 
>    
>   - if i consider a band width of more number of semitones than there would be no diffirence between the linear scaling and the semitone scaling.
>    
>   As we all know that the semitone scale corresponds the best to the musical scale, is it possible to actually implement it in designing  filter banks used  in cochlear implants? inspite of the fact that it will require more number of independent filters.
>    
>   I request members to send comments as to wheather i should continue to consider the semitone spacing for my study.
>   All suggestion are welcome!
>    
>   With best regards
>    
>   Niky
>    
>    
>    
>    
>   Dept of Speech pathology & Audiology
>   MAHE University
>   Manipal
>   India
>