On Tuesday, 10 April 2018 22:28:02 UTC+1, alan_m wrote:
On 10/04/2018 19:43, Chris J Dixon wrote:
Dave Plowman (News) wrote:

In article ,
Chris J Dixon wrote:
I tried one, and the cats and squirrels were completely
unaffected. However, my partner's rather younger ears were
sufficiently sensitive to find it seriously irritating, so it
didn't stay in use very long.

Not really ultrasonic if you can hear it?

Sub-harmonics?

I've found that you can hear them as the switch on/off but not
necessarily when they have been fully on.

if not fully on they may not be producing just untrasonic.

In the same way I can run faster than usain bolt but can't when he is running fast.
I can also run faster than a formula 1 car provided it's parked.