Hearing Aids Signals Processing

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

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

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

Example of a 2 Channel Hearing Instrument

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

Example of a 16 Channel Hearing Instrument

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 delivers the most natural sound experience in hearing instruments due to its precise emulation of cochlea functions