Mini 2018 emitting a tone..?

[HeavyMantra]

I've had this machine since late 2018. Yesterday I noticed that it has started to emit a pure tone. It's not the coil whine that has been there from the start, this is something new. The sound is loud enough to bother me. Has anyone experienced this?

If I load a page in my browser, the sound stops while the page is loading

 

[Fishrrman]

Record the sound and post a link here.

 

[HeavyMantra]

Record the sound and post a link here.

I'm currently not at home because of the virus, so I can't. It's just a sine tone.

 

[chrfr]

I'm currently not at home because of the virus, so I can't. It's just a sine tone.

Are you sure it's not just the fan?

 

[HeavyMantra]

Are you sure it's not just the fan?

If it's malfunctioning, it could be the fan. It's like a sine tone that's interrupted by the usual coil whine whenever that occurs