Annoying Feedback Noise

I am a new hearing aid user.
My hearing aid (left ear only) is an OTICON Delta (4000?).

I am annoyed by the following: even in a quiet room, nobody is present, no
TV, no radio, no outside noise etc. the hearing aid is prone to periodically start a short whistle without any apparent provocation. This feedback noise lasts a second or so and then goes away.
What is the cause of this? How can it be avoided?

Also find that s and ch and c are very harsh. What is the cause?

I would appreciate a technical explanation.

Thank you for any help.

Lentia

Hi Lentia,

I cannot help with the technical side of this, but it sounds to me that your aid is either not put in properly, or it does not fit. Have you noticed that the sounds in a quite room happen when you swallow or chew, or maybe just move your jaw?

Lentia,

It sounds like the high frequency amplification is set too high. This would explain the over sharpness of the fricative consonants. As a general rule, the more high frequency you blow into your ear, the more chance you have of feedback.

So simply having the hearing professional soften the sound by reducing the high tones, may kill two birds with one stone.

It also wouldn’t hurt to have them check your ears. Excessive wax can make feedback more likely.

Finally, ensure that the aids fit well in the ears. Poorly fitting aids can have a tendency to feedback.

Dear Helper(s),

Thank you for your reply(ies).

There is no problem with the ear canal. It is free from any obstruction.
I also think the “dome” ist fitting well.

I myself have suspected too much high frequency gain and have asked
my provider to reduce it. He did so and I noticed a slight improvement
in the understandability of the fricative sounds, but the feedback was
not greatly reduced.

Following your advice I shall go and see the hearing aid vendor again
and ask for further reduction.

The question is: What would you recommend that the corrected curve
should look like??

While I do not have a valid audiogram for the assisted ear I can tell you
that the unassisted audiogram shows the curve to be at 35 dB flat out
to 2000 Hz. It then drops off over the next 1000 Hz to 60 dB and remains
flat at that value to the top of the frequency scale at 8000 Hz.

I know it is very difficult to provide assistance based on these data, but
I would appreciate any hunch.

Thank you again

Lentia.

It doesn’t matter if the curve looks like a drunk snake. What matters is that you can hear clearly, without the unnecessary sharpness or feedback.

I think that solving one problem here, will probable solve the other.

Good luck.

Dear CZT,

I appreciate your continued interest.

Without doubt it makes no difference what the audiogram looks like after the adjustments have been made and have provided an acceptable hearing experience.

The question is: How does one get to this desirable result? So far I have the impression that the customer tells the hearing aid specialist what deficit he perceives and then the audiologist guesses as to what my be a helpful change. This is a hit and miss procedure which in some instances may converge quickly, in many others the patient may give up in frustration.

Would it not be a more logical and sound approach to measure an audiogram including word recognition after each adjustment? Then there would be a record of what the patient actually hears, independet of whether he is able to describe his hearing experience and the audiologists understanding of what the patient has tried to tell him. Any adjustment could then be based upon data containing the psych-
ological and physiological response of the patients hearing pathways.

This approach may seem to burder the audiologist with extra time spent and less profits made. Actually however it may save the audiologist time and money and the patient frustration.

What do you think about this approach?

Thank you
Lentia.

Lentia,

It sounds like it would make sense, but it’s not that easy to do what you are suggesting.

After all is said and done, you can throw a bunch of science out of the window, if you apply the text book settings to a patient and the patient doesn’t like it, you have not solved the problem.

There is an art to fitting hearing aids. An unquantifiable factor that determines success or failure (or degree of success at least). As a hearing professional you have to listen very carefully to what the patient is explaining to you and determine if the problem is mental, physical, incorrect use of the aid, incorrect programming of the aid, or physical with the aid itself. You then need to make adjustments as appropriate.

Just to make our work harder, the results may not instantly be known. Just like wearing a new glasses prescription (or bi or varifocals) it takes the brain time to adjust to certain changes. So it may take weeks and several visits to get things right.

But hearing loss is not a boolean equation. It is fitting an imperfect aid to a person with a hearing disability, and trying to manage the problem as best one can. There is no test that can be done that proves unequivocally that the fitting is perfect. You just have to try it for a a while and see.

Hello ZCS.

You are truyly an exceptional individual who will to respond several times to the same writer. I thank you and I am learning from your replies.

I agree with you that a problem with the hearing aid may have one or more than one cause from among several. This however is true for almost any difficulty in medicine or even ordinary equipment repair.

For this reason it is important to be certain just what effect a given intervention may have had. Factors such as a patient trying to mislead the
audiologist are likely to be very rare, because it is the patient who wants
to hear better and lying about what he is observing is therefore an unlikely
event. He may be of below, average or above average intelligence, conditions
which a person experienced in patient contact should be able to reliably inter-
pret. The assessment of mental problems whether they arise from lack of
intelligence and insight or rarely from mental illness is therefore not that difficult and not subject to objective measurement in an audiologists practice.
The physical functioning of the hearing aid is something the audiologist should
be an expert in assessing. Insertion skills can be checked in the office.

I see no reason to forego the one objective and repeatable test for the functioning of a hearing aid, as repeated audiology tests including speech recognition with the hearing aid INSERTED can provide. Their results and what the patient is telling about his difficulties should be the most important guides in selecting programming changes.

Another difficulty, not easily addressed, is what programming changes should be made, based upon the proposed repeat audiometry tests. If indeed these changes are nothing more than guess work, then it may be less important to
test repeatedly. In that case we are truly on a hit and miss curve. If however
the repeat audiometry tests can provide rational guidance for programming changes, then there is no reason not to perform them. Question: What are the guidelines for programming changes, where do they come from and where can one find them, if indeed they exist?

Sincerly
Lentia.

Well you are clearly a very perceptive person and and excellent judge of character :rolleyes: Even if you do always spell my name wrong :stuck_out_tongue:

Performing a hearing test and creating an audiogram is ONLY designed for testing without a hearing aid in. Attempting to obtain an audiogram with hearing aids in, is of no real benefit.

The adjustments you make as a hearing professional come from experience and training. Understanding fundamentally what kind of loss a patient has, and then simply translating what a patient is telling you into adjustments to the hearing aids.

There is no cut and dry test you can do that PROVES what adjustments are necessary.

It’s not ‘guess work’ as much as it is intelligent logical reasoning based on audiological knowledge, experience, and understanding the patient’s problems versus the technical capabilities of the hearing device being used.

Over time you get better and better at taking care of patient issues. As well as experience, there is generally a license requirement for further education where the professional receives advice about new techniques, new software and hardware, and advice on how to make a patient happy.

Dear ZCT,

I hope I spelled your “name” correctly this time and apologize for my errors.

Now I would like to get my final response to you onto the screen. There are two important items
which occured to me while I read your last mail.

Firstly you said, without justifying your statement further, that
“Performing a hearing test and creating an audiogram is ONLY designed for testing without a hearing aid in. Attempting to obtain an audiogram with hearing aids in, is of no real benefit.”
Now if true, this is a very important finding and its source must be somewhere in the literature. It would be of value to learn where and how this conclusion was reached. Can you cite any sources?

Secondly, you say:
“The adjustments you make as a hearing professional come from experience and training. Understanding
fundamentally what kind of loss a patient has, and then simply translating what a patient is telling you into adjustments to the hearing aids.”
Here you describe a basic problem. Any professional judgment must be subject to scrutiny and evaluation. This requires that the choice of one way over another can be verbalized and communicated. If this is not possible, then we are dealing with black art and the patient is compelled to place his hearing upon faith in his audiologist(s). Not a desirable position to be in and not the goal of a health profession which proudly displays audiograms, uses digital devices and deals in computer programs.

Sincerly
Lentia.

lets see regarding the first point…

  • Prior to the Introduction of REM, functional gain ( how close the aided thersholds get to normal) used to be one way to measure HI benefit.

Now it is agreed by most Prof. that this measure is not so usefull given the new tech in the new HI, Noise reduction and Feedback canceler, generally
provide inaccurate results…

The other issue is that HI are not fit to provide a 0 dbhl aided thresholds across, it is a generally accepted fact that validation should be using
REM…

I have meet people who do aided and unaided speech measures… But I have not meet a lot of people who still do this to validate fitting

Personally, I generally prefer to do REM…

“Performing a hearing test and creating an audiogram is ONLY designed for testing without a hearing aid in. Attempting to obtain an audiogram with hearing aids in, is of no real benefit.”

I recently had to undergo a hearing evaluation with my hearing aids in place. This was done to ensure that I met the minimum local Occupational Health and Safety requirements for the type of work I do - forklift / transporter driving, where the hearing loss should be no greater than 40 dB average in the better ear.

Personally, I generally prefer to do REM…

Hello Xbulder

Thank you for your reply and mentioning Real Ear Measurement (REM) as one important
aid in adjusting hearing aids by a scientific method.

I like to take advantage of your expertise. Permit me therefore to direct some questions
at you.

REM seems to be a measurement which does not take the patients auditory sensation of
the signal produced by the hearing aid into account. Rather it seems to be a method
to test the combined response of the hearing aid and the ear canal to the acoustic input.
Is this true or false?
If this should be true then the patients ability to understand speech is only indirectly addressed.
A test involving standard acoustic speech input followed by the patient’s response to what
he hears with the hearing aid would be required to test whether any adjustment has in
fact lead to an improvement. Are such tests used and if not, why not?

And now a very practical question: Suppose a customer has bought a hearing aid from
a hearing instrument specialist and the adjustments based upon this providers judgement
have proven unsatisfactory. Is there a way to find a provider who uses a currently accepted,
scientific approach to the adjustment and what costs may one expect in that case.

A reply would be much appreciated
Lentia.

Indeed you did. Thank you :cool:

I looked up some information on this subject for you. Hope that helps. Although I’m not sure why you can’t just blindly trust everything I say :rolleyes:

Audiometric testing procedure is described in Training Manual For Professionals in the Field of Hearing Instrument Sciences, KRAMA / WILSON, ISBN 0-934031-05-3. In the 1996 reprint, section 8-1 paragraph seven it explains the procedures of performing pure tone audiometry, and the importance of removing hearing instruments prior to testing.

In looking at my original references list when I originally qualified in 1994, I found some further references for you:

British Society of Audiology (1981). British Journal of Audiology 15, 213-316.

King, P.F., Coles, R.R.A., Lutmain, M.E. and Robinson, D.W. (1992) Assessment of Hearing Disability: Guidelines for Medicolegal Practice, Whurr Publishers London.

Brooks, D.N. (1989) Adult Aural Rehabilitation, Chapman & Hall, London.

I dare say that some of the Audiologists here will have a better and more current book list than I do. Especially if there is an AuD frequenting this board.

But to answer your question in a nutshell, audiometry is designed purely to determine natural threshold results in an unaided ear. You can’t just modify an internationally accepted standard test and decide to do it with hearing aids in, just because you feel like it.

The way in which a hearing aid would respond under those circumstances has not been measured (and would have enormous variance from one aid to another since they would all react differently to the headphones), and therefore the results of such a test would have no real meaning.

As an example, the Destiny/Virtue hearing aids made by Starkey have a built in telephone detection system. If you placed headphones over the ears to do audiometry they would automatically detect the increased chance of feedback, together with the magnetic field from the headphones and conclude you were trying to use the telephone. They would instantly switch into telephone mode, thus providing a completely different frequency response to their normal usage pattern.

In addition to those issues, feedback or near feedback levels would also alter the acoustic properties of the hearing aids. This is likely to happen when you place audiometer headphones over a patients ears in the manner dictated by the above referenced books. Thus also invalidating the results.

I’m sorry, but in dealing with any professional, you are going to have to trust them to some extent. When I go and get a hair cut, I have to assume that because the person has a license, they became qualified to do so.

When I go to the doctor, I have to trust that their medical opinion will be a good one, and they are doing things in the best interests of me.

When I go see a lawyer, I have to trust that they are doing things by the book to help me win a case quickly and cost effectively. I have to hope they are not dragging things out just to bill me more money.

At the end of the day, just because you would like to be able to verify the function of the hearing aid using pure tone audiometry, doesn’t mean it is possible or even advisable.

In my opinion, fitting hearing aids is a highly subjective situation. There are so many variables I could write you pages on it. Two people with an IDENTICAL audiogram, could require very different solutions. Sometimes even a solution that the text book answer would seem to contradict.

So a professional must be patient, and actively seek to understand how a patient hears, and work with them to achieve the optimum results to the best of his ability, over a period of time.

To confound this goal is the unfortunate reality that hearing is not like a light switch, you cannot just turn it on and off at whim. You fit hearing aids, which are an imperfect device, to a hearing loss that is irreversible and permanent (and maybe progressive). You then may have to wait several months before you reach optimum hearing ability with your new hearing aids (Reference American Academy of Audiology http://www.audiology.org/aboutaudiology/consumered/guides/hearingaids.htm). So fitting aids and then instantly trying to test their effectiveness is really not going to give viable responses because the “Relearning takes place in the central auditory nervous system and not in the ear itself.” (same reference) and until this process has stabilized, the results of any such testing would be questionable in terms of their validity.

I don’t know what kind of test you had. Maybe it was free field.

But if all they did was perform pure tone audiometry on you in this manner, the results are questionable at best. I think that the motivation was a ‘covering of butt’ rather than a real scientific test that would have any real validity if it were scrutinized.

While we are calling for references here, I’d like to see a book reference from the technician who did this test, showing that it was a valid and reasonable procedure, yielding useful results.

I dont think people do functional gain measures anymore, such measures are prone to errors due to noise reduction, speech enhancement and feedback supression algorithms. REal ear is the way to go…

How many of the local audis use insert phones ?
1

Hello Xbulder

Thank you for your reply and mentioning Real Ear Measurement (REM) as one important
aid in adjusting hearing aids by a scientific method.

I like to take advantage of your expertise. Permit me therefore to direct some questions
at you.

REM seems to be a measurement which does not take the patients auditory sensation of
the signal produced by the hearing aid into account. Rather it seems to be a method
to test the combined response of the hearing aid and the ear canal to the acoustic input.
Is this true or false?
If this should be true then the patients ability to understand speech is only indirectly addressed.
A test involving standard acoustic speech input followed by the patient’s response to what
he hears with the hearing aid would be required to test whether any adjustment has in
fact lead to an improvement. Are such tests used and if not, why not?

And now a very practical question: Suppose a customer has bought a hearing aid from
a hearing instrument specialist and the adjustments based upon this providers judgement
have proven unsatisfactory. Is there a way to find a provider who uses a currently accepted,
scientific approach to the adjustment and what costs may one expect in that case.

A reply would be much appreciated
Lentia.[/quote]

I believe all the prof in this forum would agree that the best way to verify a fitting is via REM. The idea is to have an independent source to measure that
you are the correct prescription at eardrum level.

your audi, inputs your audi into the PC and uses the fitting software to
program the aid. Your audi has previously selecting the fitting formula - algorithm which will calculate the optimal gain per frequency that will ensure
you are getting the right compensation … So we use a independent machine to see that what the HI is actually performing matches what the fitting software says the instrument should perform and so we see the compensation
at the eardrum level…

I know ZCT is a very hard advocate of the integrated REM for the starkey fitting, but the spirit is to have an independent source for verifications…

My brazilian friends told me it is now a law in brazil, and that each HI fit
must have a REM to it, and how they have not been force to use it…

Hello ZCT,

Thank you for the outstanding care with which you replied to my questions and comments.
They indeed were as complete and sincere as one can possibly hope for. Nevertheless
there are some misunderstandings and fundamental differences between your approach
and mine.

Let me go over the issues in no particular order.

1.) I did not advocate the kind of audiogram which you describe as a control on the effectiveness
of settings made by the dispenser. I did not say that earphones should be used over hearing aids.
In fact audiograms can and have been made with aids in the ear by using loudspeakers to
provide the acoustic signal. The setup for this should be available at all dispensers.
2.) I did not say that audiograms alone should be used. Instead I advocated the use of an additional
speech recognition test with aids in the canal to check whether adjustments have improved speech
intelligibility.
3.) I do no trust anybody based solely upon the possession of a license or a diploma! One must never
fail to use judgment and one should not fail to acquire knowledge about the issues at hand. One might
also remember the recommendation to look for a second opinion.
4.) I would also like to point out that the call to trust bearers of license and diploma has certain effects
upon the relationship between dispenser and patient. These effects are altogether undesirable.
They consist in the sparsity of information regarding the technical capabilities of hearing aids and
the details of adjustments made by the dispenser. Remember that in medicine, the details regarding
a prescribed pharmaceutical must be disclosed to the patient in the form of an extensive flyer. The
details for any prescription drug whatsoever is freely accessible in the PDR (Physian’s Desk Reference).
Any procedure performed must be documented and be presented to the patient on demand. None
of this applies to hearing aids or to their dispensers. Why not?
5.)Now regarding to your call, probably well justified, for patience with regard to fitting hearing aids.
The problem ist, that the dispensers do not make this clear, but ask you to come back in a week or two.
Furthermore the right to return an unsatisfactory aid or to exchange it, does not allow for the kind of
extended use (many months) which you describe as necessary. I do not know what the answer to this problem might be. Do you?

I now thank you for all the care in your reply and send you my greetings
Lentia.

Lentia,

  1. I think I have made it pretty clear that audiometry testing is not designed to test hearing aids, no matter how it is done.

  2. Personally, I question the effectiveness of speech tests versus real world experience.

  3. If you read my posts I have made it pretty clear that I have met many useless professionals in my time. So I certainly would never suggest blind trust. But sooner or later you have to make a determination that a professional can be trusted to a point. This can be from personal experience, or maybe a recommendation from someone you trust. If you never trust, you’re going to have problems. But healthy skeptism is always wise.

  4. Actually there are several things that are mandated by most if not all state law. Supply of technical information, extensive instruction manuals, and various other pieces of information are supposed to be provided to a patient. In fact in my state a patient must sign a fitting form to acknowledge that they have in fact received this information. I don’t honestly know how much this varies by state. But I do know that if Tennessee requires it, it is likely to be the minimum required in most other states!

  5. Personally, I always make it clear that it will take several months and possibly a significant number of follow up visits to provide the patient with the results they are hoping for (whilst also setting up realistic expectations). I don’t think you can make a blanket statement about what all dispensers do. Any dispenser that does not strongly encourage follow up visits, is just being lazy.

As for returning of aids, I believe all states mandate 30 days, and some companies offer up to 60 days. But realistically, and from a practical business standpoint this offer cannot be open ended and drag on for months. It would hurt cash flow and is simply not really viable for most dispensers to offer.

However, good factories provide for the ability to exchange or make extensive changes to a dispensing at least a year after the fitting. I know my company is awfully generous when it comes to that kind of thing.

What I keep going back to however is realistic expectations. I’ve already mentioned twice unequivocally, that learning to hear is a process, and results are not as easily quantifiable as you have hoped. Unlike glasses, hearing aids cannot restore perfect hearing. This is why I have repeatedly referred to them as an imperfect product for a problem that cannot be solved. Once the human hearing is damaged (assuming we are talking about nerve deafness) there is no way to reverse this. A hearing aid will provide nothing more than an aid to hearing. It cannot restore hearing back to where it was. All we can hope to achieve is to provide the patient with an acceptable level of speech understanding in most situations. However, what they end up with depends on the patient, how they wear the hearing aids, how they live their lives, the changes they make to their life style, the kind of life style they have, and many other factors.

You keep calling to quantify scientifically the benefits of a hearing aid. I put it to you that this is not possible. Trying to quantify in scientific terms the relative effectiveness of a hearing aid for any given individual, given the number of variables and subjective nature of the requirements of success and expectations, is simply not possible in my opinion.

You could do a 100 word speech test, and the patient scores 40% without the hearing aids in, and 75% with the hearing aids in. You could describe that as an improvement, or a 25% failure. But if that score improvement has brought about an improvement to the quality of life, then I’d argue that the fitting was a success. But what if their score only improved from 40% to 55%. Is that a failure or a success? Only the patient can know that when they live their real life. In fact, what if the patient trialled two hearing aid systems. In one the improvement in the speech test is from 40% to 73%, and in the other set the improvement is to 80%. What if the patient tells you the first set simply sounds better? Do you tell them they are wrong and that scientifically the second set is superior?

As a professional, I would not presume to tell my patient what an acceptable improvement to the quality of their life is. That is for them to tell me.

While speech disc gives some indication of how well should a client would perform in real life, I have read that the best predictor is ANL,
I would agree that real life is so complex…