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.

http://www1.umn.edu/news/news-releases/2010/UR_CONTENT_254452.html

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.

Kevin

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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?

Jeffrey

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.

Regards
Torben