hearing aid purchase

Jeffrey Sirianni audioman at hctc.net
Sat Dec 20 14:00:36 EST 1997


abcd <johnt at kcco.com> writes:

>I need to purchase a pair of hearing aids for my 3 1/2 year
>old son. These are his first hearing aids.
>
>His audiogram is
>
>500 Hz 55 db
>1000 Hz 45 db
>2000 Hz 35 db
>4000 Hz 20 db
>
>This is sometimes termed "reverse" loss (greater
>in the low frequencies).

First off, I would definitely recommend a two-channel instrument for
fitting a reverse loss.  Most traditional one-channel amplifiers are
designed to amplify high frquencies more than low frequenices.  In a
reverse loss, the patient needs just the opposite.  Before two-channel
instruments were around, the person fitting the aid would use special
earhooks, earmolds, and dampers to suppress the high frequency emphasis
in order to get enough gain in the low frequencies.  With a two-channel
device, the high and low frequency gain settings can be set independently
and so a reverse loss can be better "matched".  An instrument with
adjustable crossover (the frequency that the low and high frequency
channels cross) is definitely recommended.


>The audiologist discussed as being "good" aids
>
>Widex Senso
>Oticon Digifocus
>Phonak (with audio zoom)
>Resound (BT4)
>Sonar MultiPro

>(not necesarily recommended in this order).

Without offending any of the manufaturers (many lurk in this newsgroup),
I would say that these are all good choices, but there are other choices
that are available depending on your financial situation as well as other
factors.  I would suggest a BTE in order to get enough gain at 500 Hz
without feedback.  A BTE will also allow earmold refittings as your child
gets older and his ears grow (around $75-$100 per pair) versus any custom
product where you'll be looking at $300 and up per device each time you
have to have them re-shelled.  A BTE is also much more durable for children
than a custom product.  All of the listed products have enough long term
flexabilty for changes in his hearing, if there is any, so he is looking
to be wearing any of these for many years (5-10 years).  On the flip-side
of this issue, when better technology is available, will you be willing to
jump back in and get him new hearing aids?  It a decision that only you
can make.

>I have heard a lot of good things about the Senso, but I have reservations.
>Some of these stem from the fact that the fitting seems to be more
>subjective in this than in analogs. For example, the audiologist
>said no aided audiogram is possible for the Senso (I guess
>because the logic circuits are designed to filter constant frequency
>long duration sounds). She said the digitals were designed mainly to
>aid speech reception and the main criterion for evaluating
>their effectiveness was how the user's speech understanding
>improved.

I think what she said was that she could not make objective real-ear
measurements with these devices (although you can if you know how).
Or she could have been talking about the fitting of the Sensos by
obtaining responses to sounds generated by the hearing aid in order
to determine thresholds, called Sensogram testing.

>My son won't be able to give the same level
>of feedback about this that an adult can, and thus there will have to be
>more subjective evaluations as to how the aids are working like does
>he seem more attentive. I am uncomfortable with this.

This is the Sensogram measurement I was talking about....

>I have also read the posts discussing the volume hunting and the clamping 
>after loud noises. To me, these seem like they could be significant 
>drawbacks (maybe even more so for a child).

This is is something that can be partially resolved with advanced
adjustment of the Sensos (increasing the UCL settings), although it
takes someone with experience with these devices to know how to make
these adjustments.  Then again, when will you child be able to say
that the aids are cutting out too much.

>I also don't see the audio zoom for him since he won't be able to
>change programs. The zoom feature is supposed to be for his later years,
>but by then there may be better aids on the market. Is some other feature
>of the Phonaks that make them very good aids?

The mutiple memory capability will be something useful in the future, but
as I eluded to eariler in this post, when your child is ready to start
using the remote control, will it be time to step up to newer technology?
The Zoom capability is something very helpful as long as the child is
facing the sound source (ie. the teacher).  As soon as his head is turned
away, this feature works against the child (and teacher).

>The Resound, Oticon, and Sonar I heve not heard much about. I have heard the
>Oticon digitization scheme is not technically as advanced as the Widex and
>that the Oticon does not try to go as far in signal processing and removing
>background noise as the Widex.

I cannot comment of the Oticon vs. Widex issue.  ReSound and Sonar are
essentially the same product (two-channel, WDRC for both channels).  The
ReSound (or equivalent Sonar) products are good choices either with the
mutiple memory and remote control for future use in the Premium line (BT4)
or in the Encore line without the remote and multiple memory option.

>I have heard (again, hearsay) thet *most* aids are designed to more
>naturally fit a loss that slopes the other way, since this is a bigger
>market. Are the digitals the most flexible? If it were not
>for the clamping and volume hunting problems, and the less complete
>post - fitting examination, I would really like him to try the Senso.

A two-channel is best for this loss (see my comments above).

>I would appreciate comments from anyone, especially professionals
>and hearing aid users who have experience with reverse loss. What aids
>fit this well? What should I stay away from? What about the earmold
>for this? I would also appreciate comparisons between the aids I listed,
>or any others that may be suitable for this loss.
>
>What objective (sound booth) measurements are possible post - fitting
>with the digitals? Are the Senso and Digifocus the same? Is there any
>important information lost (especially for a child) by being able to do 
>less post - fitting measurements?

The audiologist should be able to make aided and unaided measurements in
the soundbooth with sounds presented through speakers.  She should be able
to get responses to tonal stimuli as well as speech reception.  His ability
to understand words may not be as well developed in a 3.5 year old child.

Good Luck....

Jeff


***************************************************
* Jeff Sirianni, M.A., CCC-A                      *
* Sound Advice / R.G. Delaney, M.D.               *
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