Speech and hearing loss / hearing aids

Earlier this week I remapped my audiogram onto one that had the speech banana superimposed onto it. My understanding is that as one ages the typical hearing loss occurs in the higher frequencies. The S sounds are up there. I work in dental where a whistling S can be problematic. This article explains it in simple terms: http://www.nytimes.com/2006/08/01/science/01whis.html The banana got me to thinking that if someone cannot properly hear an “S” they cannot automatically adjust their jaw and tongue positions to properly speak an “S”. So even though we can do a number of things dentally, I’m thinking that considering hearing loss and HA functioning might be part of the solution. I.e. hearing should be part of the diagnosis of a whistling problem. Are there any thoughts on that?

Funny we were just talking about the speech banana. I might try to see if there is a way to toggle that on and off on our audiograms. A project for another day.

I think frequency lowering would be very helpful for some folks to clearly hear the “s”/“sh” much better, too. Ever since I started using the Speech Rescue frequency lowering technology on my OPN, I find the “s”/“sh” very noticeable compared to before.

How does that even work?
Does your brain figure out to learn that “ah ok that’s an s/sh going on there that I now hear it differently but I gather it’s an s/sh in there”?

In yourself, others or both?

Did you have any sibilance?

My gut says it is related to how the brain processes speech. Most have seen the jumbled written words: People
Would not the visual and auditory processing be similar?

This is a loaded question since different HA mfgs implement frequency lowering differently with different strategies/technologies. I heard that frequency lowering had been a mixed bag of results because quite often people are more confused like you said because they brain are used to hearing certain sounds and certain frequencies only so now if they don’t sound the same anymore then how would your brain know what it is.

Below is a graphical description of 3 different frequency lowering strategies. The least effective one in my opinion is the compression strategy, because you actually alter the shape of the sound’s waveform and create a high risk of confusion because the sound loses its original shape and signature.

The transposition is better because it doesn’t compress sounds. But it cuts out the original sound which is a disadvantage because you no longer can hear and use the original sound as a reference anymore (assuming that your loss is not far long gone in that frequency range and the amplification lets you hear the original sound somewhat).

The composition approach is my opinion is the best because it retains the original sound at the original frequency and only “adds” the new lowered sound which is a copy of the original sound, but at the lower frequency. I think this is the best approach because it retains the original sound so people still can hear it (if they can still hear the amplified version of it) and use it as a reference. The composition approach is what the Oticon OPN uses.

The other advantage of the composition strategy is that it can capture a wider region of the high frequency band source and compose them into a narrower destination region. I believe this helps enables the frequency lowering of more high frequency sounds (over a wider band) for once. It also fits better into the natural frequency selectivity of the cochlear. There’s a natural perceptual arrangement of the auditory filter (the cochlear bandpass filter) whose width increases approximately logarithmically toward higher frequencies (the base of the cochlear). The arrangement of the composed lowered sound based on this natural frequency selectivity helps introduce minimal distortion of the lowered signals.

But to forgo the tech-speak above and answer your question more directly, I don’t feel like I have to retrain my brain to learn what the lowered sounds mean with the OPN Speech Rescue. I just instantly and naturally know that it’s an “s” sound right away, because it still sounds just like an “s” to me because it has all the characteristic of an “s”, just at a lower frequency, and nothing is lost. The same with cricket sound. It’s usually at 8KHz and my hearing is far long gone in that range and no amount of amplification by my 105dB receiver can bring it back. But as soon as I hear the lowered sound of the cricket noise, I instantly know right away that it’s the cricket sound. Same with bird sounds.

I guess another way to look at it is if you watch those movies where someone uses a voice altering device to lower the sound of their voice so nobody can recognize that it’s their voice anymore -> well, although you don’t recognize the voice anymore, you still understand fully what is being said even though the voice is lowered. It’s like that with the Speech Rescue approach, I guess.

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Both. Even hear it much more clearly on TV shows and movies as well.

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Wow Volusiano. Thanks.
Your last paragraph about voice-disguising in movies or news to protect someones identity made it all crystal clear. Interesting stuff.

That’s pretty subjective as lots of people can’t stand it. Compression can be better easier to introduce gradually for these people.

Yeah, I actually don’t have first hand experience with neither frequency compression nor transposition so I can’t really say whether they’re good or bad based on personal experience. It was just some logical reasoning I had but the reality of it may be very different and subjective like you said.

All I can really say is that the composition strategy used by the OPN seems to really work well for me personally. But the other strategies may work very well for other people as well.

Anyway, sorry to go off on a tangent here but I guess it’s still relevant and may be useful as part of the diagnosis to the whisting “s” problem when taking into consideration the hearing loss as well.

I use compression and like it. I started off gradually and have increased it to a level that works pretty well. I did notice that when I increased the strength of the settings that I had a lot of sibilance for awhile until I got used to it. I would think that people who have a good sense of pitch would hate most frequency lowering schemes.