Signal Processing

Hearing Aids, Hearing Instruments Technologies

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Digital Hearing Aids Technologies - Signals Processing

Analog Signal Processing

The incoming acoustic signal is changed into an electric signal and back into an audible acoustic signal

Digital Signal Processing

The incoming acoustic signal is changed into an electric signal (analog) signal which is then converted into numbers (Binary Code) for further processing

Advantages of Digital Signal Processing

  • Binary Code is used to process signals in hearing instruments
    • same as in PCs
  • Hearing Instruments are flexible as PCs
  • Applying features not possible in analog technology
  • Many new hardware & software features can be used to improve
    • Sound quality, comfortable hearing, wearing convenience, speech discrimination
  • Huge potential for future developments


Channels divide the frequency range of a Hearing Instrument into blocks/segments.

Each channel can be manipulated individual according to user´s requirements.

The more channels, the more accurately a Hearing Instrument can be fine-tuned according to an individual hearing loss

Signal Processing Strategies

  • digital Wide Dynamic Range Compression (dWDRC)
    • Makes soft sounds audible & keeps loud sounds comfortable
    • Adjusts amplification automatically according to input signal intensity
    • Simulates the Outer Hair Cell function of the cochlea
    • no need for manual volume control
  • dLimiting / digital Super Compression (dSC)
    • Provide more or less the same amplification regardless of the input level
    • No (dLim) or only very little (dSC) automatic amplification adjustment
    • Requires frequent use of manual volume control
  • Bionic Perception Processing (BPP)
    • Simulates the natural structure and sound perception functions of the human cochlea
    • BPP in hearing instruments uses a 20 channel DSP
  • Spectral Masking
    • Some components of sound are inaudible to the normal functioning ear because they are masked by others
    • BPP only applies amplification to components of sound which are audible to normal hearing persons
  • Loudness Summation
    • Loudness perception does not depend on sound intensity alone but also on the size of area stimulated on the basilar membrane
    • 2 sounds with different intensities and different bandwidth can be perceived same loud (see picture)
    • BPP takes this into account - dWDRC don´t
  • BPP delivers the most natural sound experience in hearing instruments due to its precise emulation of cochlea functions

Hearing Aids, Hearing Instruments Technologies

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