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Digital Hearing aid

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Pooja Yadav

The slides here cover the medical application of DSP in hearing aids. It will explain the working and processing of Digital hearing aid in detail. It will also cover the internal working description in term of speech spectrum.

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Medical Application of DSP : DIGITAL HEARING AID Applications of Digital Signal Processing in Hearing aids
Digital Signal Processing
Working : ï‚— The sound picked up by the microphone, is converted into an electric signal, and then digitized ï‚— The digital signal is then filtered to selectively amplify those frequency bands in which the patient shows the most severe hearing loss ï‚— Amplitude compression, in which the system gain is reduced when the amplitude exceeds some pre- defined threshold values, in order to avoid excessive loudness to the ear is also used. ï‚— Finally the processed digital signal is converted back to analog form in the digital-to-analog (D/A) converter, and delivered to the ear via the earphone
Digital hearing aid :
ï‚— In a further stage of signal processing in hearing aids, the amplitude-range may be compressed ï‚— Hence, the gain of the system is progressively reduced when the sound-volume exceeds a specified level ï‚— A small delay in adapting the gain to the signal- levels may also be added, as the average of the most recent amplitudes drives the gain control
How does Digital hearing aid work ?  A digital hearing aid has a small computer inside it to control  The computer memory stores setting for its user  The computer program adjust the sound to be within the user’s ‘window of hearing’ or in the dynamic range
What happens inside it? ï‚— The speech spectrum is split into bits of data ; number which can be manipulated by the tiny computer ï‚— Sound is then amplified to make them audible ï‚— Extra algorithm may be programmed by the DSP unit for feedback control, noise reduction and sound enhancement

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Digital Hearing aid

  • 1. Medical Application of DSP : DIGITAL HEARING AID Applications of Digital Signal Processing in Hearing aids
  • 3. Working : ï‚— The sound picked up by the microphone, is converted into an electric signal, and then digitized ï‚— The digital signal is then filtered to selectively amplify those frequency bands in which the patient shows the most severe hearing loss ï‚— Amplitude compression, in which the system gain is reduced when the amplitude exceeds some pre- defined threshold values, in order to avoid excessive loudness to the ear is also used. ï‚— Finally the processed digital signal is converted back to analog form in the digital-to-analog (D/A) converter, and delivered to the ear via the earphone
  • 5. ï‚— In a further stage of signal processing in hearing aids, the amplitude-range may be compressed ï‚— Hence, the gain of the system is progressively reduced when the sound-volume exceeds a specified level ï‚— A small delay in adapting the gain to the signal- levels may also be added, as the average of the most recent amplitudes drives the gain control
  • 6. How does Digital hearing aid work ? ï‚— A digital hearing aid has a small computer inside it to control ï‚— The computer memory stores setting for its user ï‚— The computer program adjust the sound to be within the user’s ‘window of hearing’ or in the dynamic range
  • 7. What happens inside it? ï‚— The speech spectrum is split into bits of data ; number which can be manipulated by the tiny computer ï‚— Sound is then amplified to make them audible ï‚— Extra algorithm may be programmed by the DSP unit for feedback control, noise reduction and sound enhancement