Have a look at this article:

http://www.hearingcenter.com/info_file...githa.html

Here I found this:

"Siemens Prisma
The Siemens Prisma dsp hearing aid is a four channel circuit that allows the audiologist a tremendous range in fitting control. The overall circuit contains a preamplifier with high level compression followed by a 23 bit analog-to-digital converter that yields a 138dB dynamic range. The digital signal processor chip operates at 150 million operations per second and is followed by an all-digital output stage to drive the output transducer (loud speaker) directly.

The four channels can use different compression algorithms to chose the temporal, frequency and amplitude characteristics to best suit your hearing loss. The channels can be cross coupled to allow the detection of speech information in the higher frequency channels to lower the volume in the lower frequency channels to reduce low frequency masking of the speech.

The Prisma offers two microphones (TwinMic™) to give directional listening in the BTE and ITE case styles. The Prisma also has two programs that can be selected by push button in all case styles except the CIC. The two programs allow the listener to switch between two different listening environments, such as speech versus music, or perhaps quiet conversation versus noisy environment."

Well, a 23bit ADC, a dynamic range of 138dB, a DSP with 150 millions operations per second and this powered by a 1.4V battery indeed looks like alien hamster technology...

Kai