Unexplained hum from PC

[Temuka]

Hi all,I have some kind of strange problem here. There is some strong hum noise coming from pc case for like 10 seconds,than silence for 5 seconds and than again 10 seconds hum. I turned off all the fans with the fan controller and I don't understand what it can be ?
It's not coil whine or some high pitched noise,it's like you hear transistor working from a long distance (but noise goes and comes back under no load)
PSU is EVGA G2 750 on silent profile also..
What can I do to resolve the problem ?
Thanks in advance.

 

[Ken g6]

Is there something in the DVD drive?

Can you visually verify that the fans are not spinning? Including the PSU and GPU fans?

Try running the computer with just the SSD, no HDDs?

 

[Temuka]

Is there something in the DVD drive?

Can you visually verify that the fans are not spinning? Including the PSU and GPU fans?

Try running the computer with just the SSD, no HDDs?

Comes out it was my 8 year old hdd As soon I tested without it,the sound was gone... In SpeedFan it says it has:

1) High Fly Writes attribute current value (1) is below the normal range (72 - 100)
2) hard disk has 165 reallocated sectors

Also it was making some weird noises during operation and turning pc on/off

I guess I have to say goodbye to old friend or is there anything can be done ?

 

[VirtualLarry]

Sounds like it could be on the way out. (8 years old? Wow, time to celebrate. Not a bad lifespan for a HDD.)

Seriously, back up what you can (or if you already have other backups), and then destroy the drive.