Case makes morse code noise when idling?

[kn1012]

It's high-pitched, though low volume. However, if I pay attention, it's there. It's an intermittent whining- literally sounds like morse code. It's pattern (not pitch) reminds me of the sound I'd hear coming from a mechanical hard-drive when working. However, I have a SSD and the noise is only apparent when the computer is idle (if click on my home button w/mouse's middle button constantly, to load new tabs -- 5 or 10 just to reproduce the issue -- the noise stops. Soon as all the instances of my home page are loaded and PC idle, the morse code resumes).

Anyone have any idea of what the cause might be? Not coming from speaker. If I shut it off and unplug, the noise still there. Not coming from CPU or case fan-- I pressed my finger on both to stop them and listen, and sound was still there.

I can't really pinpoint the source by listening, I just know it's there.

My PSU does have a bottom fan.. but why would virtual activity affect that?

Which leaves (I guess) either the motherboard, memory, CPU, or video card. (Funny, I just loaded a youtube video fulls-creen and shut off speaker- the noise went away. Don't know if that helps rule out video card..?)

I am running an old Athlon X4 760, GTX 750, on a BIOSTAR Hi-Fi A85S3 board. 2 sATA3 SSDs, 2 sticks of DDR3 1600MHZ memory. Old 450w antec PSU.

 

[The_Man12]

I'd say MAYBE it's coil whine?

 

[kn1012]

I'd say MAYBE it's coil whine?

What component would a coil whine originate from generally?

I searched youtube and found a demonstration of coil whine-- the whine/experiment starts at about 1:45 ( https://www.youtube.com/watch?v=HP73edpQwgc ) -- it doesn't quite sound like that, I think it's quieter (you can gauge it's loudness by comparing it to the loudness of the guy in the video's mouse clicks as the whining goes on) and a bit higher pitched. Though, I guess coil whines (if that is the case for me) would sound differently in different setups?

Not sure. Your input, and anyone elses?

Thanks.

Edit: by the way, in the video I linked, it occurs *during* activity. Mine is most (or only?) noticeable during idling.

 

[RaDiKaL_]

When its during idle its usually a capacitor in your mobo,if so it should hold on for a good while, afterwards (months) you'll have some trouble booting up (will take like 2+ attempts for the capacitor to get properly charged to boot up).