On Tue, 11 Mar 2008 16:53:35 +0000, Rod
wrote:

Now listen up!

The windmill thread has become unwieldy – so I am starting a new thread
though I have just been reading Dave Liquorice and Mary Fisher
discussing low frequency sound "up the way" and that is what has
prompted this post. The mosquito thread also seems potentially relevant.
The presence of several people with in-depth understanding of sound and
noise helps. :-)

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 suffer from high pitched tinnitus. Partner suffers from deeper
tinnitus. We both exhibit some signs of hyperacusis.

Neither of us noticed anything different about the store (e.g. new
acoustic tiles).

After discussing it with partner, I wondered if they could have
installed some sort of anti-noise device to reduce the sound levels in
the store?

Any suggestions? Any explanations?

I wonder if it was a "white/pink noise" source? I once worked in a
building with one of those and it had a similar effect of masking
other sounds.

M.