After trying to get back to sleep I could not help but hearing this very odd sound, like the sound coming from a propeller type aircraft in the distance but there was no change in pitch as you expect from a flying aircraft, … Formula One race cars produce massive changes in frequency. http://en.wikipedia.org/wiki/Doppler_effect Therefore if a temperature inversion exists the frequency is trapped within the atmosphere and so produces a constant noise … …

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Strange noise in the night.