on 25/05/2017, Dave Plowman (News) supposed :
I was more thinking of how to do it on the old Rover which has 'analogue'
wiring. But plenty of things that buzz or click too as warnings. Big
problem being you can't easily adjust the sound levels. The indicator
warning (for example) is to quiet. The reversing sensor one too loud.

In the day, I would quieten sounders which were too loud by sticking
bluetack over them and the ones which were too quiet I would make a
baffle for and/or make a hole in the trim. Baffle as in tube or
similar, anything which makes the air path between front and rear of
the part which moves, longer.

Remember those plug in speakers for small transistor radios, where the
speaker was fitted inside a cardboard tube?