THE DEVELOPMENT OF A DIGITAL HEARING AID DEVICE FOR HEARING IMPAIRED PEOPLE
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Hearing loss is typically measured as the shift in the auditory system relative to that of a normal ear for detection of a pure tone. Human auditory system is too complex to be imitated hundred percent. However, with the availability of modern day technologies and the recent developments in signal processing area, we can design sophisticated artificial hearing systems that relax the job of damaged auditory systems to a great extent and make much of the sound available to the hearing impaired. In pursuit of designing an artificial hearing aid, human auditory system is the best model to start with. Most hearing aids work well in noise-free environments but give poor performances in noisy environments. However with the availability of a variety of noise reduction algorithms, the background noise could be reduced to a great extent. Along with the noise reduction mechanism, the digital hearing aids apply a very precise gain only to the hard-to-hear frequency regions rather than applying a uniform gain to all the incoming signals. During the amplification process, some sounds may exceed a certain level and add to the listening discomfort of the user. Therefore the hearing aid must imply some amplitude compression mechanism to control overall gain of the speech amplification system according to the listening comfort of the hearing impaired.
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