Strange random sound-does anyone recognize this?

Vocaroo | Voice message

I am getting this sound randomly on my computer, but very infrequently. I have all windows sounds disabled, and system sounds completely muted. I even downloaded Process Monitor and followed this (How to Find Which Program Is Making Sounds in the Background?) , and couldn't seem to find anything there either.

The only things I see in sound mixer are google chrome and steam, I highly doubt the sound is coming from either of these. Please help!

Alright I tested it by running with firefox instead for a couple weeks...lo and behold the sound pops up again. Volume mixer doesn't seem to help. I'm truly clueless, this is driving me mad. It happens maybe every few days, and it seems to only happen when I'm playing a video online (browser makes no difference).

Bump. I cannot for the life of me figure out what this sound is, and its' very loud and distracting. Happens maybe once every 2-3 days, it seems to happen when I'm watching something like youtube/twitch, but it happens whether I use chrome or firefox. Anyone know where this sound might be from?

Hemimax said:

It sounds mechanical to me, or it is a virus. Check all moving parts, fans & HDD's and scan for malware.

I don't think it's mechanical, it's coming out of the actual speakers. Virus scan is a good idea. It's a new computer I have no idea how there'd be any viruses but I'll try. Do you recommend any virus scanner besides windows defender?

AddRAM said:

Maybe it comes from something else on that same webpage when you watch a video, a commercial or add.

As you say it only happens when you visit those sites.

A good idea but a week ago he wrote "Volume mixer doesn't seem to help" by which I understand that even if the volume control for Chrome of Firefox is set to 0 (while playing video online) this strange sound appears nonetheless.
The sound coming from a webpage (be it a video, a commercial or ad) is directed to the sound card as one single stream of bits, isn't it?

theridon said:

I don't think it's mechanical, it's coming out of the actual speakers. Virus scan is a good idea. It's a new computer I have no idea how there'd be any viruses but I'll try. Do you recommend any virus scanner besides windows defender?

As for viruses I would recommend Kaspersky Rescue Disk (running from a USB flash drive).

What kind of sound card do you use? 5.1? 7.1? Or just the built-in, onboard one?