Every once in a while the Sony VAIO speakers on my generic PC (Abit NF7-S V2.0 motherboard) make a weird sound when nothing is playing through them. The sound is a bu-bup bu-bup bu-bup bu-bup, not high pitched and not low just weird.
I also get this when I have my iPod attached to my Jimmy's cassete player. That sound appears randomly and over songs that are currently playing.
Maybe the sounds aren't really the same but they sure seem the same when I hear them, any guesses?
Is the 'fridge, a/c, furnace fan, etc. running? Look for sources of RF interference when it happens.
Hmmm, my PC is less than 5 feet from the furnace, and it did notice the sound again tonight less than a minute after adjusting the thermostat. I'll continue observations...
That doesn't explain the iPod though.
It's your cell phone
Genius.
After years of holding out I finally caved and got a cell phone. As I hate them with a passion I tend to keep mine set to silent with no virbration alert so if it's going off in my bag under my desk I don't know. Last time the sound appeared my cell phone was on my desk and I got a call shortly after the sound, very shortly.
More observations to make.
It took me about three months to figure out that it was the cell phone that was making that sound in my office... and in my car... and at home...
(Sometimes I'm about as sharp as a sack of wet mice)
Anyway, why do it do dat?
I've noticed that my cell phone does weird things to my speakerphone at work too...even when I'm not actually on the phone at all.
It does the sound thing because quite simply it's GSM. GSM makes a small signal to the tower a few seconds before you get a call, to alert the phone that a call will be coming in. CDMA phones (Verizon and the like) do not do this because they are in constant communications with the tower.
My phone is CDMA and it does it all the time. PCS phones do it much worse though.