On Mon, 06 Jul 2009 12:04:57 +0100, "Dave Plowman (News)"
wrote:

In article ,
JohnT wrote:
Thanks for the comments.
What I am trying to do is to optimise a voice signal in the presence
of high background noise levels, so I need a fairly sharp bandpass
filter.
I have of course tried simple RC sections for HPF and LPF but this is
not sufficiently sharp for the purpose.

Better way might be to use a noise cancelling mic.

This is true, but I am assuming he doesn't have access to the source,
and is trying to make the best of what he is receiving.

Somewhere in a junk box I have a pair of throat mics that used to do
service in a Lancaster bomber. They are quite uncanny - you could use
them next to a revving F1 car, and hear nothing but the voice. The big
problem is that they don't catch any kind of sibilant, so you have to
be careful what words you say if you want to be understood.

d