How to improve speech intelligibility in hearing aids?

Question by al mond: How to improve speech intelligibility in hearing aids?
Since World War II, people have known that speech intelligibility can be improved by increasing the consonant amplitude compared to that of the vowel. Why isn’t this capability incorporated into hearing aids, turning them into understanding aids?

Best answer:

Answer by Technobuff
I’m just left wondering how to filter out the vowels only, in order to boost the consonants!? Or vice versa.
I don’t have a hearing aid or work with hearing aids, but I think that customising the response to various frequency bands to suit the individual aid wearer’s hearing would be a more suitable way of improving understanding.
Add noise cancelling as well….?

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2 Responses to “How to improve speech intelligibility in hearing aids?”

  1. Mr. Un-couth says:

    Hearing aids are just about as good as the test equipment used and the knowledge and experience of the person who conducts the frequency response test on your individual ears. The test determines what frequencies within the audio frequency spectrum that your ear needs to have amplified and by how much so that sounds are normal rather than distorted. It takes several different frequencies to stimulate your ear to produce a particular undistorted sound. If your ear does not respond to all of those frequencies required to produce all the sounds then normal speech sounds distorted.

    The trick to a successful hearing aid is to have an accurate frequency response test ran on your ears and then have the hearing aid tuned to amplify the audio frequencies that need amplifying and passing the other audio frequencies on as is.

    If the frequency response test determines that your ear responds poorly to all audio frequencies then the hearing aid can be tuned to amplify all frequencies the same and amplified enough so that the sounds are at the desired volume.

    If the frequency response test determines that your ear does not respond at all to certain audio frequencies then a hearing aid can not remove the distortion.

  2. tat says:

    Viewing speech from the perspective of consonant and vowel is not very useful as the majority of the languages in the world are not based on this. The more accurate modeling of human voice is LPC (Linear Predictive Coding). From wikipedia (http://en.wikipedia.org/wiki/Linear_predictive_coding):

    “LPC starts with the assumption that a speech signal is produced by a buzzer at the end of a tube (voiced sounds), with occasional added hissing and popping sounds (sibilants and plosive sounds). Although apparently crude, this model is actually a close approximation to the reality of speech production. The glottis (the space between the vocal folds) produces the buzz, which is characterized by its intensity (loudness) and frequency (pitch). The vocal tract (the throat and mouth) forms the tube, which is characterized by its resonances, which give rise to formants, or enhanced frequency bands in the sound produced. Hisses and pops are generated by the action of the tongue, lips and throat during sibilants and plosives.”

    The latest technology in hearing aids is digital processing. Improving speech intelligibility is just one domain. This is called “Digital Speech Enhancement (DSE). These systems act to increase the relative intensity of some segments of speech. Current DSE processing identifies and enhances speech based either on temporal, or more recently, spectral content. DSE in hearing aids is still relatively new, and its effectiveness is largely unknown”.

    Other digital technology to improve hearing aids are:
    1. enhanced gain control, either automatic or intelligent
    2. feedback reduction
    3. noise reduction
    4. synthetic directional microphone
    5. custom shaping of emphasis filters

    On noise reduction Sony’s latest digital technology has artificial intelligence. See http://www.wired.com/reviews/product/sony_mdr_nc500d


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