Question on Audiogram and Frequencies Tested

Hey Guys,

A question on audiograms.
I had another one done yesterday as part of my routine to check on my ears - and all was normal (slightly better) than the one two years ago. So other than having to listen for the "warble" through a head of hissing tinnitus, I was happy.

I had an interesting discussion with the audiologist (which she initiated) on why I have tinnitus with no significant hearing loss.
She said that conventional hearing tests only test up to 8khz (I know this, and I've had an extended one done a little while ago), they only measure intervals. So in between these intervals, there could be a dip at a certain frequency which is responsible for our tinnitus (as well as frequencies above 8khz).
She said you can get audiograms done that test more of the frequencies (they obviously take longer), which might expose where exactly a loss might sit.

Now I haven't really cared to educate myself too much on hearing tests and losses, rather focusing on tinnitus and how I can lessen that burden on myself.

Does anyone have any feedback on this? Even if we are told we have no losses in the speech range, this is only in the frequencies tested and won't expose anything that lies in between?

Thanks Guys!

Samantha.

 

Yup, unfortunately the test is only a sample of a few frequencies (a few octaves apart actually) up to 8 kHz. An extended test can be done for higher frequencies, but again it's just a sampling of a few frequencies, and anything can go in between. It's harder to go above 8 kHz due to the equipment needed (mostly headphones).

In addition to this, because of hidden hearing loss, you can ace the test and still have synaptic damage...

So the test is a nice high-level thing to do (if it shows damage, you know you have damage, but if it shows clear, you don't really know for sure), but one should understand its limits.

 

Or you could have perfect hearing at extended high and low frequencies without gaps and still have T from a somatic source! For my trial we did a very extensive hearing test in order to customize the background stimulus and I believe it was 5x the number of intervals and from 100HZ to 16khz. I guess there could still be gaps but it would be very odd.

 

@GregCA
Thanks for the reply and confirmation.
How do they go about programming hearing aids then? Is it enough to just amplify the tested frequencies and that will support any losses in between?
I had an extended audiogram two years ago, shows some losses at and above 8khz, so I know there is some hidden hearing loss there...
Apparently you can get an special audiogram done where it can test in 5-10hz intervals, but that would take a very long time and I'm not even sure where I'd go to get that done.

 

@kelpiemsp
Absolutely. I don't have somatic tinnitus, but yes, there are other factors at play other than hearing loss. Identifying these is what's difficult.
Ah, needle in a haystack. It's so overwhelming when you just want answers.

 

Hearing aids are optimized for speech and most amplify frequencies up to around 6kHz, although I believe a few on the market amplify somewhere up to the region of 8 - 10kHz?

The audiogram is the "prescription" for programming a hearing aid; it uses the audiogram data to calculate the likely amount of amplification needed (i.e. gain) although it gets a bit more complicated than that

 

@Samantha R it is I'm sorry.

 

Yes (sort of): if you've ever played with a music equalizer you probably remember those little sliders for each frequency "band". For example you had one for 1 kHz, but when you slid it up, it wasn't "just exactly 1 kHz pure tones" that were enhanced. In digital signal processing, it's a whole band that gets an increase or a decrease (it looks like a bell curve that you pull up fro the middle: the side frequencies also get a boost). Hearing aids are essentially fancy sound equalizers.

It's enough lift with adjacent frequencies that you can "fill the gaps" between the actual sampled values. For example, if you lift 1 kHz by 10 dB and 2 kHz (an octave higher) by 10 dB, the "in-between frequencies" are also going to get a boost (more or less equal to 10 dB too - depending on the type of digital filter used).

Be careful to not confused hidden hearing loss (synaptopathy) that can affect any frequency (even under 8 kHz) with high frequency hearing loss, whose "hidden nature" is just derived from the fact that audiologists typically don't test above 8 kHz. If you've found losses above 8 kHz, they're not necessarily hidden (in the Liberman's sense).

Because our hearing uses log scales, the steps are probably logarithmic too, but more granular than the current "standard test" (which is roughly one sample per octave). Maybe you can get 100 data points instead of 6, but for many hearing aids (if I recall well), the programming user interface only takes the standard data points as input, so the extra data would be good for your own understanding of your hearing, but I'm unsure it could help in setting up your hearing aid.

 

Be aware that loss above 8k is not unusual, even at a young age. A study looking at individuals with exposure to loud noise and ototoxic medications versus individuals with normal hearing found high frequency loss begins in childhood even for those with normal or minimal loud noise exposure.

For example, in the chart you can see that 25dB hearing at 12hz for 10-30 year olds was considered normal. At that same frequency, nearly 40dB was normal for 31-50 year olds.

It is difficult to assert whether high frequency loss is abnormal. Unless you have significant loss putting you multiple age groups ahead, for example if you’re 20 and at 60dB for 12hz.

Or if you have hearing loss in only one ear. If you have loss in only one ear, then you could compare both ears and see an obvious 15dB or greater difference suggesting more loss in one ear versus the other. This is the case for me.

Here are the full study results: http://ispub.com/IJORL/10/2/4039

 

Samantha?!?!!!