Rod wrote:

The other day I went to Tesco at Loudwater. (What an exciting life I
lead!) Something seemed odd throughout my visit but it really became
obvious while at the till. I couldn’t hear properly any more.

It felt like being in a dream. The checkout operator must have said
something but their voice was distant and quiet. The beeps, rattles, and
other common din at the till was much less obvious than normal.

Usually in this particular Tesco (and many other stores), I find the
volume unpleasant, almost painful. The racket made by the refrigeration
plant is bad and varies in bands or rays or nodes up and down the aisles
(never have quite worked it out) where (I imagine) the sounds from
various sources interfere. The noise of the tills is annoying.

But this time it was almost like the air was not transmitting sound as
well as usual. I did not notice the refrigeration plant nearly as much
as usual.

On leaving, my hearing initially felt dampened down as if I had become
partially deaf. It seemed to recover over the next tens of minutes. And
I mentioned the experience to partner. She felt almost exactly the same
as I had.

I was once walking down the Strand one lunch-time, when I suddenly
became aware that I could only hear with difficulty - it came on
suddenly, lasted a couple of seconds, then cleared. Very strange. Then
a few moments later it did it again.

I realised that I was walking in the same direction as the traffic,
and I was alongside a London taxi. Every time the taxi put its brakes
on, I went deaf without hearing anything.

I realised the taxi's brakes were squeaking quite loudly, but at a
frequency that I couldn't hear - my cut-off these days is about 11
kHz.

I wonder if your Tesco is countering the ambient noise by turning
people's hearing down in this way? It might have the added benefit of
stopping youngsters buying booze, hanging around, etc etc.