[asterisk-users] hum noise

[Chris Bagnall]

> I'd suggest calling an echo test or playback(silence) extension on your
> asterisk from the SIP phone.  If there's hum, then it's almost certainly
> coming from the phone (my bet would be a dodgy power supply).

Probably also worth checking there are no cellphones near either endpoint. They seem to have a habit of introducing hum into otherwise perfect calls.

As an aside, one does wonder why there's such inadequate shielding against interference on SIP phones, given that most environments in which they'll be used will also have a cellphone on the desk.

Regards,

Chris