Can it be done?

Jeffrey Sirianni audioman at HCTC.NET
Mon Jan 27 00:55:25 EST 1997


bp293 at FreeNet.Carleton.CA (Robert Matylewicz) writes:

>What I am hoping to find is a hearing aid that can boost the 2k+
>frequencies to help me understand conversation (I don't hear the
>sibilance). One ITE pair I tried (around $900) did help in this
>way BUT the compression circuit took away the dynamics (change in
>voulme) of the music. I asked the audiologist if a 'defeat' switch
>could be incorporated so I could either use the compression to
>protect my ears from unwanted loud sounds (squeel of bus brakes)
>OR turn off that circuit so that the *dynamics* of the music
>wouldn't be altered.

There are some two-channel devices where one band is linear while
the other is compression (i.e. Oticon Multifocus).  Can anyone
clarify or verify this, and if so, which one is which?

It sounds to me that you are looking for a device where you can
adjust the compression kneepoint yourself before entering different
listening conditions.  You might consider a multiple memory programmable
device, although this is more expensive than you are paying right now.

>After checking with the manufacture, the audiologist sent the
>aids back for this operation. What came back was nothing like we'd
>hoped for. Turning the switch off (eliminating the compression
>circuit) dropped the volume to almost nothing. And the frequency
>curve (the high end boost) was nothing like it had been before the
>change.

I'm not sure why this happened... Any thought out there ??

>Another phone call to the manufacture and the reports is that
>it's *because* of the compression circuit that the high end boost
>can be achieved. The high end boost comes from the compression
>circuit. At least this is what I understand the situation to be.

Sounds like some sort of TILL circuit.... Makes sense....

>I assume my wish for a 'simple' bypass switch isn't possible
>because all these circuits are inside a chip and you just can't
>get into those chips to do any rewiring.

>Has anyone come across this kind of request before? Can it be
>done in a pair of hearing aids costing under $1000 (Canadain).
>I'd just like to know what's posible and for what cost before I
>make this rather major purchase.

>Thanks in advance for any help, ideas, or solutions you might be
>able to offer me.

Good Luck.....

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