Hearing aids

G. M. Alf gmalf19 at nwlink.com
Fri Aug 23 11:17:48 EST 1996


>I believe GHI claims their CIC with the Intrigue circuit is a dual channel
>aid because the "Intrigue" is actually Gennum's Dynamic EQ 2 Circuit.  The
>DEQ2 is a user-friendly (another word for non-programmable?) dual channel
>amplifier which separates the incoming signal into high and low frequency
>bands. The bands then are independently expanded/compressed before they
>are once again joined and amplified. 

The bands are not independently expanded or compressed.  The input
signal is first sent to a 2:1 companding circuit and then to the band
split filter.  Next comes the companders for both bands.  The "amount"
of companding is separately controllable by pots.  Gennum claims that
multiple AGC control blocks isolated from each other can lead to
serious distortions in the time-domain response of the system.  To
avoid this they use what they call synchronous companding which is a
single AGC control mechanism that controls all three companders.

>In my conversations with other manufacturers, I have been told that the
>DEQ2 is Gennum's way of giving Mead Killion (K-Amp) and Resound (WBDRC) a
>run for their money.  I have dispensed a lot of DEQ2s, though, and my
>patients have been extremely satisfied with the results.  Functional gain
>and real ear measurements have also been encouraging.  The crossover
>frequency option puzzles me though--I seem to have better luck matching
>target with an active tone control.

What problems are you noticing?

>The crossover options seem to work a little better in the Resound and Siemens
>Music programmable products.  But perhaps I may be expecting too much from
>a non-programmable hearing aid.

The Dynam EQII circuits are programmable but they use an analog system
(pots) rather than a programmer and a digital controlling circuit.

Mike





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