Dave Liquorice wrote:
On Sat, 03 May 2008 18:05:47 +0100, Peter Scott wrote:

Yes I wondered about that. I thought perhaps bats used much higher
frequencies than the repellers, about 150 kHz and higher.

Depends on the species, most use bewteen 20kHz and 100kHz:

http://www.bats.org.uk/helpline/help..._bat_detectors.
asp

I wonder if the sound can cause them direction problems if it leaks out
through the roof? I suppose they would 'see' the radiation as a solid
wall and so avoid it?

Peter Scott