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I
have on occasion heard a strange noise that occurs between midnight
and sunrise. It is low in frequency with a slightly varying amplitude
and sounds like a lorry engine running in the distance, not idling like
others have reported, but as if the lorry is stationary in neutral
with a foot lightly on the accelerator, or when a lorry is struggling
up a hill with a heavy load. This is no lorry though because it goes on
for hours at a time and only at night. Maybe it's only noticeable at
night because everything is quiet and still. I first become aware of it
in the bedroom, but once noticed it can then be heard around the house.
The sound seems to stop if I open a door or window to try and hear if
it is coming from outside. I have thrown the main
circuit breaker to the house to shut down all electric appliances and
still it persists. I have pressed my ear to the adjoining wall of my
neighbour in case there is a fridge or something on the other side, but
I hear nothing. This is a very interesting mystery!
Many years ago when I still
lived
with my parents, I recall hearing a
similar sound and wondering what it was. That was about 3 miles from my
current location, the Medway Towns in Kent, UK. Back then I only heard
it a couple of times but now I notice it more often, especially if I
can't sleep and am awake into the early hours. I've researched the
phenomenon and
found that others around the world have had the same experience,
although
there seems to be places where it's more common, the UK being one of
them. Some think it's a form of tinnitus, which I do suffer from, but I
know it's not the same. Using a tone generator, I have
worked out that my tinnitus has a main frequency of about 8Khz (there
are other frequencies of lower amplitude mixed in there as well) but the
'Hum' that I experience is about 95Hz.
I
Know I have an intolerance of deep bass. When
someone drives past me with a sub woofer booming, even for a few
seconds, I instantly get a headache and may even feel physically
sick, which can last for some time afterwards. I was once actually sick
at a live music event because of the deep bass! Where I used to work, I
remember some earth works being carried out
nearby that were producing incredibly deep vibrations which only I
seemed to
notice. It was so bad that I had to get away
from it whilst my colleagues carried on blissfully unaware. I found it
unbelievable that they couldn't hear it, although I guess it was more
of a feeling than a sound. Perhaps a perception. I
guess some people are just more sensitive to it than others. Or maybe
it is just a form of tinitus!
Some interesting links: Wikipedia World Hum Map Tone Generator Changing Opinion |