High pitched buzzing sound trough speakers

[harkzep]

Hi wonder if anyone can help?
In my home studio I keep getting a high pitched buzzing noise coming from my speakers every five minutes or so, these noises come in 2 to 3 intervals at about 3 seconds long. I am using an external terratec sound card but was having the same problem when a sound blaster fatality xfi card was installed internally. When the external card is removed and plugged into my laptop in another room this problem doesn't occur? At first I thought it was the casing on the speaker cables not being thick enough and running close to power supply's, but I have the same problem when my Sehnisser Hd25-1 are plugged directly into the monitor output on the sound card. I also have this high pitched buzzing intervals on my 5.1 home cinema system in my living room. I know it's not much info to go on but any help would be very much appreciated.
Thanks in advance.

 

[MrWrenchey]

My initial thought (dunno what you mean by buzzing noise, perhaps post a recording of it if you could mic up your speakers?) would be that it's a cell phone that's nearby that's causing it.

 

[ecc83]

The fact that it is a high frequency noise would seem to rule out mobile phone in my view.
These tend to produce a very characteristic "gallop" pattern of noises and sometimes a quite low frequency buzz in the 250Hz region I would say. This is the RFI from the PHONE. i do not know what the transmitter sound like. I shall try to get a recording of my phone to compare.

The fact that the laptop is unaffected but other mains powered equipment is suggest the energy might be mains borne? You could try one of the so called mains "conditioners". I am not a fan as a rule but might be worth a try in this instance. Don't buy a really cheap "Walmart/Rockbottom device and make sure it includes "RFI" filters, not just "surge suppression" (which is rarely needed and generally doesn't work anyway!).

Here in UK we used to have an excellent band of engineers who were part of the then General Post Office and were tasked with tracking down and fixing (including confiscating equipment and prosecuting offenders where appropriate) all form of broadcast interference. Sadly those chaps have gone the way of the Dodo (i.e. hunted to extinction by rabid privatization!) and Ofcom now deal with such complaints and if they are as good at that as Regulators are at reducing "roaming charges" and sorting out greedy b'std energy companies/banks etc, GDE'LPUS!

Dave.