John Doe writes:

I always knew they enjoyed listening to the outside sounds. That was made
clear when a newly adopted stray always napped with its head against the
speaker, as the speaker was moved around.

Thank you, I appreciate your explanation. It's an interesting idea --
it's good that you noticed what they like.

Incidentally, outside we have one of those PIR-activated ultrasonic
noisemakers protecting a patch of lawn, after I got fed up of having to
pick up all the neighbour's cat's faeces each time before I get into
mowing the grass. Now the cat just hisses at it from atop the fence and
walks across our decking instead (which I don't mind if it doesn't
defecate all over it!).

-- Mark