[charles1948]

What I'm seeking is an explanation of how it does it.

It has a large, rapidly varying current running through it, and a magnet wrapped round it.
Since it's not infinitely rigid, it will vibrate.

 Thanks BC.  At least you seem to share my disparagement of the ridiculous notion that the loud noise given out by a microwave oven comes from its fan.  I mean, who could believe that?

Obviously, the source of the noise is the magnetron. 

Yet, I sense there is some sensitive territory involved here.  Possibly involving government-induced magnetron-denial, owing to fears of the magnetron's weapons-potential.  If disclosed to the public.

Therefore I won't pursue this any further. I don't want get arrested.
So let's just agree that the noise from a microwave oven is caused entirely by its fan. And leave it at that.

Phew! 









Can't the vibrations be damped out?  To  get rid of the

[evan_au]

the ridiculous notion that the loud noise given out by a microwave oven comes from its fan.

Even the quiet fans in laptops can get a worn bearing, and start making a loud(er) noise.
- Fans don't cool so well when the fan doesn't rotate freely

Maybe it's time to replace your microwave?

[Colin2B]

Thanks BC.  At least you seem to share my disparagement of the ridiculous notion that the loud noise given out by a microwave oven comes from its fan.  I mean, who could believe that?

Me for one - and @Bored chemist  didn’t say it couldn’t come from the fan.
As has been said, fans in microwaves are not expected to be quiet so customers don’t complain, but none of us like noisy computers. Hence fans in microwaves can have lower spec sound reduction eg less balanced, lighter weight supports.
Same is true of the turntable motor and stirrer and their drive systems, all of these make significant noise. As @evan says,  bearings (often cheap ones) do wear.
The transformer can also be a source of buzz or hum.
There is some value in having a microwave that makes noise , it sounds as though it’s doing something.

Obviously, the source of the noise is the magnetron. 

All the magnetrons I’ve worked with are silent, except when getting to end of life when they can get noisy.  How long have you had it, was it always this noisy?

Yet, I sense there is some sensitive territory involved here.  Possibly involving government-induced magnetron-denial, owing to fears of the magnetron's weapons-potential.  If disclosed to the public.

You sense wrongly.
I would be wary of starting any form of conspiracy theory as they are unscientific, may be harmful, and we are taking action against those who spread them.

[charles1948]

 When you say: "we are taking action against those who spread them [ ie false conspiracy theories],  will your  "action"  take the form of the traditional night-time arrest, followed by incarceration and torture in the rumoured Naked Scientist interrogation cells?  In order to beat me into confessing to an entirely false conception of microwave-oven noise.

When you do it, can you let me be naked in the cell.  And get beaten by completely naked guards.

This would really turn me on.  As it might the guards.  Also perhaps some Moderators,  who would of course be overseeing it all?

[Colin2B]

When you do it, can you let me be naked in the cell.  And get beaten by completely naked guards.

Payment in advance please, this isn’t free on the NHS.

[evan_au]

the rumoured Naked Scientist interrogation cells?  In order to beat me into confessing to an entirely false conception of microwave-oven noise.

No. You are just locked in a cell with the sound of a loud microwave oven.
And no tinfoil from which to fashion a skullcap.