Grave, mechanical or engine-like sound but constant without any external source. No directional identifiable. Felt like present everywhere. No variations. Persistant and monotonous during night hours when no other sounds intefere. Any time of the year. It's fine.
Madrid, Spain · 2018-07-08 · from the WORLDHUMMAP archive
An account in Madrid, Spain
What they reported
First noticed: 2010
Pitch: Close to 90 Hz Sine.
Loudest: During the night
Where: Indoors
Symptoms: Ear discomfort (pain, fullness, throbbing);Sense of vibration;Anxiety
Changes with weather: No.
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This is a Hum report from Dr Glen MacPherson's World Hum Map, an open, worldwide record of people who hear an unexplained low-frequency hum. Reproduced with permission and with thanks; the project is at thehum.info. We remove anything on request. Location shown is approximate.