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dB reference for acoustic reflexes

Maxianne Berger maxib at CAM.ORG
Sat Nov 23 15:20:10 EST 1996


On 19 Nov 1996, Jeffrey Sirianni wrote:

> Forwarded from personal email received:
> >Date: Mon, 18 Nov 1996 17:49:10 -0800 (PST)
> >From: nancy nigg <nancy_nigg at csufresno.edu>

> >Can anyone explain why ipsilateral reflexes are measured in dBSPL
> >while contralateral reflexes are measured in dBHL?  I have searched a
> >number of books and can not find the reason why.  Any help would be
> >appreciated.  Thanks, Nancy
> >
This is a guess.  Contralateral reflexes are delivered by earphone or
insert microphones in *relative silence*.  Both modes of delivery have
established reference zero for hearing level.  Calibration according to
ANSI etc standards with couplers appropriate to type of receiver is
fairly straightforward.

Ipsilateral reflexes are measured with an insert **in the presence of the
probe tone**. For there to be a reference zero in dBHL, someone has to
establish the "normal" hearing threshold for each of the test tones in the
presence of a 220, 440, and 660Hz tone of some 90dBSPL ... It is obviously
easier to just keep an essentially suprathreshold measure in SPL, since in
this case, there are far too many variables affecting the calibration.


                     =================================
                      Maxianne Berger * maxib at cam.org 
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