Why does my PC speakers pop when light switches are used ?

July 4, 2007 11:54 PM

Why does my PC speakers pop when light switches are used ?

I recently moved my office at home to a different room.
Since then, I hear a loud pop from my pc speakers when a light switch or power outlet is switched.

I have a tumble dryer in the laundry below, it's new, and when it runs I get a pop every time it switches direction.

It's driving my wife crazy when she works from home.

It is annoying, and turning the volume dow does nothing.
My pc and speakers go through an APC ups, though he speakers are only on the surge protect, not the battery.

Why does it pop ?
Is it going to do any damage to other equipment ?
Can I stop it ?

Thanks

posted by matholio to home & garden (8 answers total)

You might have an electrician have a look at it, as it might be a sign of some kind of wiring fault.

You might try putting the speakers on the UPS, but I doubt that will help since you're running on the AC when the AC is available.

You can probably solve it by upgrading to a line-interactive UPS, in which the computer constantly runs off the battery which is charged continuously from the AC, rather than quickly switching to battery when the AC goes out, but they are expensive.
posted by kindall at 12:12 AM on July 5, 2007

The pop is caused by electrical arcing. Which often means a poorly designed or failing electrical switch. What to do about it depends on how faulty the switch(es) are. An electrical arc creates a lot of electromagnetic noise and lots of things can pick it up. If the arc is small it is probably being transmitted along the wires. You can buy a filter at your local electronics store, but they don't work well with spikes of noise. (Or at all really.) Best bet is connecting something to a different circuit.

If the arc is big and close its conceivable your speakers is picking the noise up from the air, not the wires. The only two options there are fix the switches (not a bad idea) or moving them further away.

Have you tried plugging the speakers through a battery powered plug?
posted by Ookseer at 12:41 AM on July 5, 2007

It's almost certainly a wiring fault somewhere in your home. Do you have a modern fuse box? I'm guessing not because otherwise each "pop" would throw the circuit breaker. I'm guessing your fuses are literally wire fuses.

The good news is that any electrician will be able to diagnose a fault like this in a matter of minutes. Getting it fixed might be expensive, however.
posted by humblepigeon at 12:56 AM on July 5, 2007

I've actually asked this very question before. You might find some of the answers I got helpful.
posted by epimorph at 3:20 AM on July 5, 2007

Put your ear close to the switch in question. Move it slowly from "Off" to "On". If you hear a tiny, barely audible "Bzzt" (or see a blue flash) you need to replace the switch. Hell, replace it anyway, most contractors use the cheapest switches money can buy. This is a trivial exercise for normal single-pole switches (turn of fuse, verify with $2 tester that electricity is off, unscrew wires from switch, replace wires in new switch, all screws back where they came from). If this $10 fix doesn't solve it, call an electrician.
posted by Skorgu at 10:13 AM on July 5, 2007

This same thing happens in my college dorm. Nthing crappy wiring.
posted by fvox13 at 2:30 PM on July 5, 2007

Thanks all.


My fuse box relatively new, the fuses are small rectangle modules with either a push/pop button or a flick lever.

I will replace the light switch which causes the most pops, as it's kinda tardy.

But I really want to know why, when the clothes dryer is operating I get a pop each time it reverses direction.
My thoughts are the dryer (cheapish) just switches polarity on a dc motor or something similar.

I'm concerned that the arcing that was mentioned may one day become house-burning-down.

I guess I'll note which switches make the 'pop', and contact an electrician.

Oh, the 'pop' I hear is because speakers convert electicity into sounds right ?
Presumable all devices on the circuit get the spike too, is it going to damage anything ?

Are PC PSUs design to deal with this ?
posted by matholio at 6:01 PM on July 5, 2007

Switchmode PSUs in general (and PC's specifically) are stupidly, idiotically robust, I wouldn't worry about those pops hurting one. A good ("Line-interactive" at least, "dual-conversion" or "on-line" if possible, see dansdata for more info.) UPS will solve any potential problems (including the dreaded heavy-wallet issue).
posted by Skorgu at 9:06 AM on July 6, 2007