[Asterisk-Users] Woodpeckers

[Nick Bachmann]

> Hi Michael,
>
> Michael Welter wrote:
>>  the codecs I use?  Filter-out everything between, say, 55 and 65Hz?
>
> Notching may not be that effective, as it will not deal with the
> harmonics. The analogue to digital converter should already be
> filtering  below 300Hz, so you probably have quite a lot of hum if it

300Hz is pretty high to filter out... it's still well within the rage of
voices. To compare, 300Hz is about a diatonic concert D.
> gets through  that. There isn't much you can do to eliminate the hum
> your callers  hear. For your own hum, additional filtering may be
> beneficial. This  could be implemented by analogue or digital filters.
> Simple RC analogue  filters probably would not be sharp enough to give
> much benefit, so you  would need a more complex active analogue filter.
> A digital filter would  require no hardware changes, but you need
> someone who knows what they  are doing to implement it for you.

Then how about something like http://www.digitimer.com/research/quest/? 
It seems to take care of harmonics and specifically targets the 50/60Hz
range.
Nick