Possibly Solved? "Interference" buzzing sound coming from KRK monitors

[DaveElson]

Hello

I have a pair of KRK Rokit 5 speakers, a few years old and just recently they (both) have started to put out a slight buzzing sound every few minutes. This lasts about 10 seconds. It's similar to the kind of sound a demo vst may produce.
I believe it must be coming through from the power supply as it occurs with the computer switched off. I have 2 computers in the room and tried to isolate by switching items off one by one.
I have changed power cords and moved the cords to different sockets in my surge protector but to no avail.
I can't work out why it would be so random.
I contacted KRK and while they were sympathetic and helpful I had already tried their suggestions.
Has anyone any suggestions? It's only happened recently and the only change I made was to purchase another computer, mainly for music stuff. But again, it happens when this computer is turned off, although I suppose I could still blame Windows 8!
Appreciate any advice.

[Frantz]

I am thinking ground loop hum which can be very difficult to resolve. In my case, it was coming from the cable TV line. If you have a coaxial cable in the room, try completely disconnecting the wire. The cable box doesn't have to be on for the hum to occur.

The thing that puzzles me is that you say it only last for a few seconds rather than being constant.

[Bhan]

See if you get the same intermittent sound with the input cables pulled. That will let you know for sure if the issue is internal to the speakers. If it's occurring in both speakers simultaneously... that might suggest that it's in your audio interface.

[nofrets]

This is kinda weird - I just noticed my Rokit 8's doing the same thing this morning. In my case, turned out to be a bit of corrosion in the level controls on the back. Gave 'em a shot of contact cleaner and a bit of a wiggle, all's well. Hope yours is as easy to resolve.

[ionized]

Sounds like it might be an RF interference issue. Try turning off all RF producers (cell phones, wireless land line phones, wireless router, etc...) and see if it stops.

[DaveElson]

Thanks for the replies. I took the cables out but it's still happening. Will get some contact cleaner and try that.

Edit: I'll take the batteries out of the wireless phone in the room too.

[Tricky-Loops]

Maybe there is some radio mast or sender nearby? My speakers are sometimes briefly beeping because of mobile phone transmitters but I've never had any continuous buzzing...

[DaveElson]

Maybe there is some radio mast or sender nearby? My speakers are sometimes briefly beeping because of mobile phone transmitters but I've never had any continuous buzzing...

Actually, there is a house up the street where it looks like someone is a radio ham. Has a huge antenna in the yard.
The frustrating this is while I haven't timed it, it's sort of like clockwork. The sound seems to last the same each time, and it's every couple of minutes.
I do have a wireless router but can't switch off yet, the wife is looking at houses and kitchens

Edit: I do live in an older rambler (1950's) and I have one of those adapters that uses the electric supply as ethernet, feeding my ROKU box. Might have to look at that, although again, it comes and goes.
Appreciate the help.

Edit 2: Not too sure yet, but as I went from one place to another on the internet, I saw that someone complained that his subwoofer was creating a problem. I just turned mine off (it's in another room too)and I think it helped. I haven't heard the hum come back in a short while. May be too soon to say but it normally would have surfaced by now. Fingers Crossed.