we have a similar issue to everyone above, we put the noise initially down to a very old wireless system so we purchased a new Sennheiser Digital system
we continue having the same noise issues with the new mics (belt pack mic particularly)
I have tried over several weeks to eliminate issues turning off various items during the service but we get the same noise around about every 20 minutes
the best way I can describe the noise is a bit like a clowns horn – never heard anything like it on wireless mics
anybody got any clues as to what it could be ?