[stylin19a]

kinda like mosquitoes.
It's the female of the species that bites but doesn't buzz.
The male doesn't bite but makes a buzzing sound trying to attract the female.

So, if you are almost asleep and hear a buzzing in your ear, don't worry about.
But...
If you are almost asleep and hear nothing...

[samtheman]

Or, as they saying in the Marshall Islands regarding taking a shade break under a palm tree, “A falling coconut makes no sound.”