What could this strange vibration noise be?

Here is a sample you can listen online on Whyp.

Other recordings can be find on GitHub.

What I have confirmed are:

It is not ambient
It often has an area of effect with a radius less than 1 meter
It is distinct from some other normal vibration sources
The centres of occurrence can be ordinary things, sometimes right at my head
There can have multiple occurrences at the same time
Since the area of effect is small, the occurrences I noticed were around/at my head
It is faint most of the times, tend to be louder at night with the quietness of night considered
Sometimes a centre of occurrence seems to be able to move
Other properties such as pitch(frequency), volume(strength) and size can also change or vary

It has been a few months since the first time I noticed it around my head when I was sleeping.

What could it be?