Why Digital?

Programmability

Just as personal computers can become word processors or a game consoles in a few seconds, computer technology in hearing aids can allow a single instrument to be tailored to meet the needs of many individuals.  For example, a digital filter can be reprogrammed from emphasizing low frequencies to emphasizing high frequencies.  In a traditional hearing aid, the circuit components would have to be re-soldered.

Stability

Analog components such as resistors, capacitors, and amplifiers, perform differently with changes in temperature and humidity.  Analog circuit components also are subject to aging which alters their behavior.  Digital signal processing removes these variables.  The digital signal processor may be programmed to detect changes in the mechanical parts of the hearing aid and adjust the sound of the hearing aid to compensate for these changes.  For example, the Widex Senso adjusts the performance of the hearing aid when it detects a change in the microphone noise.

Repeatability

Digital  hearing aid circuits are very reliable.  Given the same program, they will all perform exactly the same way. Analog circuits will perform within a certain range or tolerance.  Each analog system has to be adjusted as they are manufactured to meet these tolerances.

Adaptability

Digital hearing aids can adapt to changes in the environment.  The adjustments are calculated and new instructions are given to the hearing instrument.  Some very basic adjustments are possible with analog hearing instruments, but the ability to change a complex set of filter characteristics is beyond the capability of analog or conventional signal processing.

Unique Processing Schemes

Steep notch filters to remove an unwanted sound, and active feedback reduction control are possible in the digital domain.  This type of manipulation is not possible in an analog instrument.

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