Seniors Health 2006-10/2hearing

Why do hearing aids amplify so much noise and make sounds too loud, but not clear enough? Seniors Choice Newsmagazine, October 2006 Among the most frequent complaints voiced by hearing aid users are that noise is amplified too much and that certain sounds become too loud for the user to bear. Most modern hearing aids contain sensors that allow the hearing aid to detect sounds exceeding a certain loudness level, and then self-adjust to reduce the amplification (gain) for those sounds. Unfortunately, because noise is comprised of many of the same frequencies as speech, it is virtually impossible to "shut out" noise without also adversely affecting the quality of the speech signal. The good news is that audiologists have learned to utilize modern technology to measure and control the maximum sound intensity reaching your ear. If sounds (speech or noise) exceed either the saturation level (maximum level the hearing aid can amplify without distortion) or your personal loudness discomfort level, distortion or discomfort will be the result. Modern hearing aids utilize technology that allows for adequate gain for soft sounds while minimally (or not at all) amplifying loud input signals. With regard to clarity, even the most sophisticated hearing aids' ability to clarify speech is limited by the degree of distortion coming from the inner ear and/or central auditory nervous system. If you have a hearing loss there are two things that occur. The first is that sounds become quieter so that they are no longer audible. Hearing aids very easily solve this issue of audibility. They simply amplify sounds to a level where you are able to hear them. The second thing that happens with most types of hearing loss is that sounds become distorted. This distortion unfortunately cannot be fixed by means of surgery or through amplification. In a quiet environment, the distortion is usually not obvious enough to interfere with people's hearing. However, in an environment where there are competing sounds (ie. along a noisy street or in a loud restaurant) the distortion becomes a lot more obvious. If you have problems with your eyes/vision the same type of thing happens. If you were to look at a very simple drawing of a stick figure, you would likely find that it would look fuzzy but you would probably be able to make out what the picture is. However, if you were to look at a highly detailed painting with lots of different colours and lines, you would likely not be able to make out what the colours and lines are representing. You can see the colours in the painting but you lack the visual acuity to determine where one line begins and the other line ends. The stick figure is like listening to someone talk in a quiet environment. While their voice may be a bit 'fuzzy' you are still able to understand what they are saying. The highly detailed and colourful painting is like listening to speech in a noisy room. You can hear the sounds of the person's voice that you are listening to, just as you are able to see the colours of the painting. However, you are unable to make any sense of what the person is saying as all the other noises (colours) blend into one big 'mumble-jumble' of sound. As I have mentioned in previous columns newer developments with multiple (directional) microphones are allowing hearing aid users to function better in noisy environments. The hearing aids cannot fix the distortion coming from the inner ear, but they can reduce the effects of the distortion by simplifying the auditory environment. In other words, the hearing aids are able to effectively reduce (not eliminate) background noise levels. If you have any hearing-related questions please send them to me at This e-mail address is being protected from spam bots, you need JavaScript enabled to view it or submit them directly to me at either of my offices. Colin VanBergen is a clinical audiologist, and manages both the Kelowna and Westbank offices of the Okanagan Hearing Clinic.

 

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