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Re: Hearing Loss "False Positive"

I did a quick, very unscientific test in a class the other day (about 30 - 35 students age mostly 19 - 22). It's done this way.

Step One
I whisper to the class. I whisper, if you can hear this put up your right hand. I repeat it a few times, slowly getting louder. The hands start to go up. A few don't go up.

Step Two
I have the class hold their pinna hard back against the sides of their head. I repeat the whisper, slowly increasing my level. It takes longer for hands to go up, but I am starting to watch for the 'late risers'. This is in the course of a demonstration about a function of the pinna.

Step Three
The class hold the pinna away from their heads. I repeat the whisper slowly increasing the level. I am now watching the late risers more closely.

Step Four
The class cup their hands behind their pinna. I start the whisper at a lower level. The hands continue to go up in about the same order as in the previous steps.

At the end of this, I speak the phrase. All hands go up.

There were 5 or 6 whose hands did not go up during steps 1 - 4. I asked the class if any of them were aware of having hearing loss, around 5 put up their hands. (Not completely the same ones as seen before.)

I have done this in various ways over the years in many classes. Some students just don't want to participate, but based on my current very unscientific, very informal 'test', I place the figure at around one in five or one in six; 15-20%. From my experience with a 'general public' in their teens and 20s, I think this percentage is lower than found in the general population. That's my estimate.

But this is also why I came to professionals with the question in the first place, one week ago today.

Would anyone in the professional community care to comment on this?

Begin forwarded message:

A new study from the University of Minnesota says that we're overestimating the amount of teens with hearing loss. 


My interpretation of the response from this list, and three other local and international lists is that there is a deep underlying concern that is surfacing. I had asked similar questions a decade ago and barely got a murmur.



On 2010, Sep 28, at 5:45 PM, Jeffrey Willson wrote:

Okay then, bottom line, what's your estimate of the percentage of teenagers who actually have a measurable and persistent noise-induced high-frequency hearing loss?


On Tue, Sep 28, 2010 at 8:14 AM, Torben Poulsen <tp@xxxxxxxxxxxxxx> wrote:
Dear List,

Thanks to Al for a clear explanation and 'calm down' statement.
I can add to things

1) In the audiometry standard ISO 8253-1 'Basic pure tone audiometry' an example is given for the uncertainty: "The expanded measurement uncertainty is evaluated for the determination of the hearing threshold level of a test subject using air conduction audiometry at a frequency below 4 kHz without masking and assuming that the requirements on ambient noise are met and that no further uncertainty contribution arises from any other
sources. The uncertainty budget then has a form as presented in Table A.2.
---I omit the table ---. The result is: Combined standard uncertainty: u = 4,9 dB.
Expanded measurement uncertainty for 95 % coverage probability, rounded to the nearest full decibel: U = 10 dB."
In other words there is a 10 dB uncertainty in the measurements itself - for frequencies below 4 kHz. The uncertainty will increase at higher frequencies (e.g. 4, 6, and 8 kHz)

2) It is well known that a fake hearing loss is often seen at 6 kHz when thesholds are determined with a Telephonics THD39 or THD49 earphone. This 'hearing loss' is about 5 dB and is possibly caused by an error in the reference value for audiometer calibration (for this specific earphone). This is mentioned as one of the conclusions in the Schlauch & Carney paper that the UMNews refer to.