Re: cochlear-amplifier

[Michael RAPSON <MICHAEL.RAPSON@xxxxxxxxx>]

Dear Mitchell,

Thanks for your email.

I started the discussion you are presumably referring to on the cochlear-amplifier mailing list to discuss a very specific behavior that I observed in a particular time domain model, which happened to be linear and passive. The conversation has gone down a number of interesting side avenues as discussions do, but the focus has stayed on certain topics of interest to that list. I say this only to point out that the discussion does not reflect disinterest in the points you felt were missing, but rather focus on other questions. For interest sake, the cochlear-amplifier mailing list started in November 2007 when a series of in depth debates on the topic of cochlear modeling on this list lost the interest of many of the people on the Auditory list. It was started as a place where modeling ideas could be discussed in detail. 

Regarding what might have been your main concern expressed: "Itâs not just âDas Ohrâ but the whole system response to radiation of âacousticâ vibratory energy and the information it carries." Certainly, the behavior of the whole system is what we ultimately want to understand, but this can only be discovered by detailed study of the both the whole system and its sub-parts. Therefore, a detailed study of one subpart is entirely appropriate and regularly done. 

You note: "The response of both ears via the CNS should be fully considered in evaluating the role played by the various elements of the peripheral sensors, which should also include the whole body sensing of very long wave length acoustic energy." Certainly this type of model is what many people are working towards. However, there are real constrains in terms of the anatomical and physiological information available, as well as time and computational power. Models of this kind are simply prohibitively expensive currently. The various cochlear models are steps in the right direction, and obviously biological research is also advancing which provides the data needed for a model of this kind.

Kind regards,
Michael


>>> On 2011/04/07 at 08:53 PM, in message
<20110407200703.055C74FEA@xxxxxxxxxxxxxxxxxxxxxxx>, Mitchell Cotter
<mcotter7@xxxxxxxxx> wrote:
> April 7, 2011
> 
> To: Andrew Bell, Michael Rapson and the
> cochlear-amplifier@xxxxxxxxxxxxxxxxxxxxxxxxxxxx 
> 
> In reading the many comments on the properties of the cochlear-neural
> processing of sounds I note some concepts that do not seem to be given much
> attention in the discussions, though generally there is acceptance of the
> presence of some active amplifying processes in the sensory system.    I
> offer consideration of a few points that may aid integrating the various
> observations and theories towards understanding better, the whole-animal
> response as part of the concerns.
> 
> *+* The response of both ears via the CNS should be fully considered in
> evaluating the role played by the various elements of the peripheral
> sensors, which should also include the whole body sensing of very long wave
> length acoustic energy.
> 
> *+*Note for example, that the ISO-220 (2003) revised *Equal Loudness
> Curves*reveal an
> *extraordinary* rise in low frequency SPL required for equal loudness, over
> the entire spectrum below 1 Khz.      A look at those curves also shows that
> the threshold across the range below 1 kHz is correspondingly extremely
> elevated.   These 2003 curves show that*:*  *@ 31.5 Hz* free field Equal
> Loudness sound of  20 phon requires *77dB more SPL *than the 1* kHz  SPL;  
> *40
> phon  requires *34dB  more SPL *and* *80 phon  requires     *30 dB more SPL
> //    FURTHER note that*
> 
>  *at 63 Hz* the increases for equal loudness are somewhat smaller; 20 phon
> requires   *48 dB more SPL *than the 1 kHz SPL;  40 phon requires *33 dB
> more SPL; *80 phon requires *18 dB more SPL .*
> 
> This loss of sensitivity at the longer wavelengths corresponds with the
> relative increased level of what might be termed background low frequency
> noise level from natural low frequency energy (even in a natural environment
> outside of populated areas).
> 
> The role of noise â particularly 1/f noise as a stimulating component of
> sensors (dither?) should also be considered as part of the system analysis
> and of course in model development.
> 
> *+ *Interestingly, a* *whole animal body responds to acoustic and ground or
> contact-borne long wavelength vibration. This all suggests that the role of
> sensory processes should be considered from a perspective of the *entire
> information receiving system *â i.e. whole animal response.
> 
> Itâs not just âDas Ohrâ but the whole system response to radiation of
> âacousticâ vibratory energy and the information it carries.
> 
> Regards to all,
> 
> Mitchell Cotter
> 
> mcotter7@xxxxxxxxx


 

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