I experience similar phenomena, and am undecided whether it is tinnitus, or
the much publicised low frequency hum, which seems to be prevalent in some
parts of the country.
It has been ascribed, variously, to eddies in gas pipes, factories, nearby
diesel generators, or deliberate LF propagation.

Look up "Low Frequency Hum" on the web - some quite surprising information
is available.

CK
"Joe Egginton" wrote in message
...
Hello All,

Since last Sunday night (9th October), I've heard a low frequency hum.
It's especially can be heard downstairs. If I go outside, it's less by
the house, but moving away the house, it's inaudible.

The only two nights it wasn't audible was last Wednesday and Thursday
night.

Could the atmosphere be increasing the range of nearby factory noise. The
nearest factory is about 2 miles away.

Joe
Wolverhampton
175m asl