Frank Erskine wrote:
On Wed, 13 Sep 2006 10:22:02 +0100, The Natural Philosopher
wrote:

Phil Anthropist wrote:

Digital hearing aids are available from NHS audiology centres but you have
to specifically request digital. There is usually a waiting list for digital
but they will supply a non-digital aid first.


No, today most will supply digital as standard. Certainly at the sorts
of amplification levels needed, analogue would be almost impossible to
achieve without feedback.

With digital ones, is there a propagation delay through the aid à la
DAB radio? My mum's losing her hearing a bit...

Yes. Thats why they work better. I assume they use DSP's rather than
analogue shaping of the spectrum, and probably use delays to control
feedback,..anyway there is always some delay through a digital
filter..thats how they work...