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Re: Eckard Blumschein: Perception of irregular short pulses

Dan Ellis wrote:
> Dear List -
> Eckard Blumschein of Magdeburg sent me the enclosed message for your
> consideration.  It describes some intriguing problems of investigating
> the sound of arc-welding (!)
>   DAn.
> ------- Forwarded Message
> Date: Thu, 02 Oct 1997 17:40:49 +0200
> From: Eckard Blumschein <blumschein@E-Technik.Uni-Magdeburg.DE>
> I recently realized a most convincing theory by Jont Allen explaining
> dynamic range of hearing. He says, stiffness of basilar membrane is slowly
> adapted to intensity of excitation via changing length of outer hair cells.
> My question is, how fast does this active feedback ease and rebuilt tension
> of BM?

The response of the hair cell length/force has been shown to follow the
in the cell, which is limited by its membrane time constant. Experiments
shown this time constant to be about 1 to 1.2 ms. Thus, the release time
be very fast, but the recover time would be 1.2 ms.

> Our recording system adapted itself to maximum of sound pressure. As a
> consequence no peaks were cut off. If, however, a simple sound card was used
> for recording the narrow spiked signal, then inevitably almost all spikes
> were rigorously clipped to the same length because the sound card adapted
> very slowly to mean value of sound signal.

You should get a better ADC. One that has no AGC or is more linear.

> Certainly, human outer hair cells can not respond in time to an incoming
> needle of sound. Corollary: Sudden sound pulse might hit basilar membrane
> before it is adapted by eased tension. The loud crack has an other, a
> physically plausible reason, too. Here it is worth to be noticed merely
> because it might give a deeper insight in how single bangs, cracks, and
> clicks are perceived.

There is significant dispersion by the BM before the signal reaches the
There has been quite a bit of work on impulsive noise by the Army. It
has been
published in JASA.

> Sincerely,
> Eckard Blumschein, 1997, Oct. 1
> Otto of Guericke University Magdeburg
> Dept. of Electrical Engineering
> PSF 4120
> D-39016 Magdeburg
> Phone:  + 49 391 67 12403                       Fax: + 49 391 67 12408
> blumschein@et.uni-magdeburg.de
> ------- End of Forwarded Message


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