latrobe,
There's lots of blood flow to the brain passing right by the ear's sensory organs. Sometimes we are more sensitive to it especially in the quiet or with any blockage to the "outside world" perhaps even with higher blood pressure or flow.
Once we concentrate on it, human nature being human nature it's effect seems louder and louder.
It will probably pass as mysteriously as it came.
Now for the joke: Try not to think about it....yeah, right?
Is your blood pressure higher than normal since the whooshing started?
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