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Thread: Why Don't Hearing Aids Cause Damage to the Ears?

  1. Default Why Don't Hearing Aids Cause Damage to the Ears?

    With some people fitted with hearing aids that have certain frequencies amplified by 70 DB or more, why aren't their ears permanently damaged?

    Since the human voice produces an audible sound of about 60 SPL DB and if that frequency was amplified by 70 SPL DB by hearing aids, the ear would receive a total 130 SPL DB which is well beyond where permanent ear damage can occur.
    Last edited by MikeF; 09-07-2011 at 04:35 AM.

  2. #2

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    I don't think you will find anyone who this level of amplification is undamaging, but the option is to not hear. Overall, discussion of this topic is taboo (ignorance is bliss).

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  3. #3
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    Quote Originally Posted by MikeF View Post
    With some people fitted with hearing aids that have certain frequencies amplified by 70 DB or more, why aren't their ears permanently damaged?

    Since the human voice produces an audible sound of about 60 SPL DB and if that frequency was amplified by 70 SPL DB by hearing aids, the ear would receive a total 130 SPL DB which is well beyond where permanent ear damage can occur.
    I'm not a pro but I don't think most hearing aids produce that much sound. 60 DB sounds get boosted, as well as 30 DB and 80 DB sounds but there is a limit. My UCL (uncomfotable level) is set to around 117 but it would have to be a loud sound to get to that level. Most things come in somewhere between 40 and 105, depending on the frequency. I don't need that much boost in the lower frequencies and there is not that much sound coming in, in the higher frequencies, in human speech. So those high frequencies are getting hit very, very briefly.

    In your example, if a person had 90 DB of loss and there was speech at 60 DB, the hearing aid should be set up to boost that only up to where the person could hear it, maybe 100 DB (boost of 40DB), even if the hearing aid was capable of boosting things up 70DB.



    Freq . Left . Right . . . Word Recognition Details and Equipment
    250 . 25 . 20
    500 . 20 . 25 . . . . . . SRT L/R = 60/55 , WRS @ 105 L/R = 80/84%
    1000 . 30 . 40 . . . . . Resound Future from Costco (April 2011)
    1500 . 50 . 55 . . . . . Phone Clip+ (May 2013).
    2000 . 50 . 65
    3000 . 70 . 85
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    8000 . 75 . 85

  4. #4
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    Quote Originally Posted by MikeF View Post
    With some people fitted with hearing aids that have certain frequencies amplified by 70 DB or more, why aren't their ears permanently damaged?

    Since the human voice produces an audible sound of about 60 SPL DB and if that frequency was amplified by 70 SPL DB by hearing aids, the ear would receive a total 130 SPL DB which is well beyond where permanent ear damage can occur.
    Quote Originally Posted by zafdor View Post
    I don't think you will find anyone who this level of amplification is undamaging, but the option is to not hear. Overall, discussion of this topic is taboo (ignorance is bliss).
    Eh?

    If I say: not true, does it save me having to explain a lot of stuff about conductive losses gain rules, compression and the like?
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  5. #5

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    Quote Originally Posted by Um bongo View Post
    Eh?

    If I say: not true, does it save me having to explain a lot of stuff about conductive losses gain rules, compression and the like?
    Also dB HL vs. dB SPL?
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  6. #6
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    Quote Originally Posted by prodigyplace View Post
    Also dB HL vs. dB SPL?
    Yes, but that's just the semantics (Also dB(Aeq)).

    It's the original statement that I object to - the one that infers that hearing aid manufacturers and audiologists are deliberately making people's hearing worse in the long term. It's ill-informed nonsense, but I don't want to appear 'combative' or 'lacking in class' in terms of my response.
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  7. #7
    DocAudio Guest

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    Hearing aids don't function in terms of dBHL since that is a formula used to simply create an audiogram where normal can be represented by a nice, pretty, fairly straight line. They function in terms of dBSPL which is the sound pressure level (SPL) of a sound when it reaches the tympanic membrane (eardrum). Sounds that are at the very extremes of frequencies (very low and high) have to have a higher SPL in order for us to hear them as opposed to the ones in the middle due to the natural resonance properties of the ear and how sound waves travel through air. The ear is not a linear system so 1 decibel of sound in does not equal 1 decibel of sound out...it varies by intensity and frequency of the sound.

    Even high-frequency emphasis hearing aids aren't able to get 50 or 60dB of gain (volume) much beyond 3000Hz due to the limitations of the electronic components. Even if they could, people that would require this much volume at those frequencies wouldn't get any benefit (most likely) because amplifying sounds that much at those frequencies would cause a significant amount of distortion. Plus, they most likely have little-no functioning hair cells in the ear to send the signal to the brain to begin with (cochlear dead zones) so trying to stimulate something that is probably not there won't do any good.

    If you combine all this and add in the limiting properties of the hearing aids, how the ear works, and the amount of gain needed to make speech audible, it results in very few people being amplified to a point where it causes further loss. Those that are, are generally in the severe-profound range in the low - mid frequencies and for them it doesn't really matter because they need to hear. It's a choice of hearing and having potential further loss or not hearing at all. I will also add that for most of these people the additional loss is minimal. I have a couple patients who, when I program their hearing aids, I get the dBSPL warning and their hearing hasn't changed at all over the past few years. It's a pretty high level also, usually around 125-130dBSPL...in order to exceed that their hearing has to be pretty bad.

  8. #8

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    The aids you see discussed on this forum are designed with limiting factors intended to keep sound from being amplified to damaging levels. Still, I take my aids out of my ears and wear foam earplugs when I'm using noisy power tools or in a very loud environment where speech comprehension is impossible in any event.

    Search around the web or watch late night TV and you'll see advertising for el cheapo analog hearing assistance devices that are designed to boost a wide range of hearing without limiting factors, and with those, I'm sure you can do some serious damage to your hearing.
    2013 Audiogram
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    R...15.......20........30........40........40..... ..30.......55.......55........65

    Speech disc:
    L: 100% at 60 dB
    R: 100% at 60 dB

  9. #9

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    Quote Originally Posted by Um bongo View Post
    Eh?

    If I say: not true, does it save me having to explain a lot of stuff about conductive losses gain rules, compression and the like?
    No, educate me.

    Agreed on the conductive losses, I can understand that as an exception. since the conducted loss is in effect an attenuator to what the cochlea is exposed to. I don't see how compression/gain rules or the like would change the fact that a power aid can easily put out 130dB if you allow it to.

    Perhaps a more insightful discussion is what exactly are the parameters of loud sounds that can cause permanent hearing loss. I personally take the somewhat ignorant and conservative approach that if I'm exposed to anything over 80db SPL c weighted average I wear hearing protection.

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  10. Default

    I'll admit that my example indicates extreme hearing loss but even a typical person with 30-40 SPL DB amplification for some frequencies falls into the danger zone of having their hearing damaged during normal conversation, watching tv, or normal daily activities.

    It is generally accepted that 90 DB sound levels for 8 hours a day and 100 DB sound levels for 2 hours per day can cause ear damage. Therefore people that had 30-40 SPL DB amplification would likely be in environments daily that could produce those sound levels.

    If those levels of amplification could produce ear damage, you would think that an ENT or audiologist would warn people to stay away from vacuum cleaners, dishwashers, clothes dryers, air conditioners, walking in city streets, noisy restaurants, or even background music without ear protection or possibly removing the hearing aids. Also you would think that the ENT or audiologist would recommend that a person use headphones instead of hearing aids when watching tv since headphones do not over amplify deficient frequencies and it is likely that the person will hear the tv better than with hearing aids.

    So it appears that amplification for someone that doesn't hear certain sounds has a different effect on the possibility of damage to ears than over amplification of sounds for people with normal hearing. It would be nice to get some hard facts about hearing aids and ear damage instead of just speculation (lot of speculation on the Internet) so that each of us can try to create an environment that enhances our lives. I have yet to see an ENT indicate that properly adjusted hearing aids will either cause or not cause ear damage.
    Last edited by MikeF; 09-07-2011 at 01:04 PM.

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