Re: two-tone suppression ("Richard F. Lyon" )

Subject: Re: two-tone suppression
From:    "Richard F. Lyon"  <DickLyon(at)ACM.ORG>
Date:    Wed, 21 Sep 2005 19:14:14 -0700

At 4:21 PM +0100 9/21/05, Ben Lineton wrote:
>Two-tone suppression can also arise from cochlear nonlinearity, as 
>evidenced by mechanical measurements of basilar membrane 2TS (sorry 
>I can't remember the reference), and by measurements of 2TS in 
>otoacoustic emissions (e.g. Brass and Kemp, Suppression of stimulus 
>frequency otoacoustic emissions, J Acoust Soc Am. 1993 
>Feb;93(2):920-39).
>
>Put simply, the suppressor tone drives the cochlear amplifier into 
>saturation, so that its response to the probe tone is reduced.

Ben,

I agree that the main source of 2TS is cochlear nonlinearity.  But 
the nature of that nonlinearity is not "saturation".  Rather, it's 
more like an automatic gain control, in which the mechanical gain 
gradually reduces as a function of mechanical response level over a 
very wide dynamic range of input power levels.  I think all the good 
mechanical BM data of recent decades support this view pretty well.

Dick