[RESOLVED] Random Speaker Noise

[MartinLiss]

Fairly frequently I hear random noise from my computer's speakers which sounds like several tapping sounds followed by a trill. The sound does not increase in volume when I turn the volume up. The noise has persisted through two sound systems and now two completely different computers, one a PC and one an iMAC. Any ideas as to what could cause the noise?

[Nightwalker83]

Do those computers share speakers?

[MartinLiss]

The only computer I have now is the iMAC, but as I said, when I used this sound system with my PC (and at the time it was the only computer I had) it had the same problem.

[baja_yu]

You could get static when turnning on/off high consumption devices if their not grounded properly.

[TheBigB]

Are they external speakers or internal?

If they are external it is probably interference on the powerline generated by the computer systems.
Try putting the speakers on a different electrical group and see if it disappears.

[MartinLiss]

No everything is grounded and there's no connection between the noise and my turning anything off or on, but I currently have my modem and Ethernet adapter sitting on top of the main sound/base unit. I'll move them off and see if I hear the noise any more.

Oh, and if by "static" you mean a crackling sound, it doesn't sound like that.

[MartinLiss]

Are they external speakers or internal?

If they are external it is probably interference on the powerline generated by the computer systems.
Try putting the speakers on a different electrical group and see if it disappears.

They're external so I'll try that too.

[MartinLiss]

Some more info about my setup.

My PC is plugged into a UPS device and my speakers were plugged into the 'Switched' side of a surge protection power strip which eventually is plugged into the same wall outlet as the UPS. I've now moved the plug for the speakers to a different outlet (which probably still shares the same circuit as the computer) and I'll see if there's any more noise. I sometimes don't hear it for a few days but I'll let you know.

[MartinLiss]

Just heard the noise

[CVMichael]

Try posting here: http://forum.allaboutcircuits.com/

Maybe they can help ?

If you record the sound, post it so we can hear it, it will probably help diagnose the problem.

[dbasnett]

"The sound does not increase in volume when I turn the volume up." Do the speakers have a volume control, or are you speaking of the PC's volume control?

Remove the UPS from the mix and see if that helps.(turn it off and take it to another room.)

I have a speaker system that doesn't like cell phones

[MartinLiss]

"The sound does not increase in volume when I turn the volume up." Do the speakers have a volume control, or are you speaking of the PC's volume control?

Remove the UPS from the mix and see if that helps.(turn it off and take it to another room.)

I have a speaker system that doesn't like cell phones

Yes the speakers have a volume control (take a look) and I don't know if the noise responds to the iMAC's volume control since I pretty much always use the speaker system's volume control.

[dbasnett]

Yes the speakers have a volume control (take a look) and I don't know if the noise responds to the iMAC's volume control since I pretty much always use the speaker system's volume control.

You would think if the "noise" is being induced into the speaker system it would get louder if the speaker volume control is increased.

[MartinLiss]

Yes, I agree, but since this has also been a problem with different speakers and a different computer, what coiuld cause it?

[FireXtol]

So the problem seems independent of your PC and speakers.

Seems you used the UPS with both? I'd guess it's your UPS. Those often make noises(described as "clicking" or "tapping"). Call it an aural illusion?

[MartinLiss]

I think the start of the noise predated the UPS but I'm not sure.

[Lord Orwell]

do you hear the sound when your cell phone is off? I've experienced a noise just like yours when someone nearby is getting a call. This may be verison or att only as my sprint phones don't do it.

[dbasnett]

do you hear the sound when your cell phone is off? I've experienced a noise just like yours when someone nearby is getting a call. This may be verison or att only as my sprint phones don't do it.

I think I alluded to the fact that my speakers make noise when near my cell.

[MarMan]

If the volume doesn't increase when you turn the volume up then it seems to me that stray EMF is causing it, entering the circuit post volume control (POT). Just like a CB can come over your TV. The source can be anywhere, an appliance, a neighbor. Next time you hear it disconnect anything you can to see if something you have is causing it. If you're not causing it you may have to shield them somehow or live with it.

[CVMichael]

You all assume that if you change the volume and the noise is the same then it's something "outside" the sound card.

A sound card is basically an amplifier, and an analog to digital converter.

The sound is converted from analog to digital, processed (change in volume, equalizer, etc), then changed back to analog and finally amplified a little bit more with the final power amplifier.

Here is a simple diagram I made in MS Paint:


The volume changing happens in the "DSP", after that you have a DAC, and then "Power Amplifier", that means that those always have the volume at MAX, therefore if there is any problem/damage in one of those, it will have the same sound intensity regardless of how the volume is set.

That's why I was saying to post in an electronics forum, because those guys can explain you this much better than me.

[TheBigB]

You all assume that if you change the volume and the noise is the same then it's something "outside" the sound card.

Well it does happen on two entirely different systems, so may I say it is a fair assumption that it is outside the soundcard.
I'm not excluding that though.

[CVMichael]

OK, I guess I did not read the entire thread...

I took a look at the speakers, and if you click on "In the box" tab, then you can see that it has an "AC power cord", this means that the speakers have their own power amplifier.

So the same idea of what I explained before it could happen here. The volume changes before the final power amplifier, and probably the noise is IN the power amplifier, therefore the same noise intensity regardless of the volume.

[MartinLiss]

OK, I guess I did not read the entire thread...

I took a look at the speakers, and if you click on "In the box" tab, then you can see that it has an "AC power cord", this means that the speakers have their own power amplifier.

So the same idea of what I explained before it could happen here. The volume changes before the final power amplifier, and probably the noise is IN the power amplifier, therefore the same noise intensity regardless of the volume.

Thanks but this has happened not only over two different computers, but two different speaker systems.

[CVMichael]

but two different speaker systems.

The same sound ??

Were they plugged in the same power outlet ?

If different power outlets, then that would be really weird, because I cannot imagine some other electronical device powerful enough to induce the sound in the speakers. It must be something with a huge power consumption, like a welder maybe?

But... again... can you record the sound, and post it here? that will help a lot in diagnosing the problem.

[MartinLiss]

No, it's the same power outlet and I don't have much choice about that unless I want to run some wire in the crawl space under the room. We don't have any huge power-consuming devices. I'd guess that the biggest ones are an upright freezer, the pool filter pump and the TV. I'll see what I can do about recording the sound.

[MarMan]

You don't need a lot of power if you have the right frequency. Could even be a refrigerator. You can use a UPS (unplugged) to determine if the source is the line. If its not the line it most likely is another electrical device, which you can find by trial and error or an EMF detector.

[Lord Orwell]

even a ups plugged in should work. The power circuit is isolated from the wall.

[namrekka]

Most UPS don't produce a nice sine wave. This can cause some interference. Try to bypass the UPS with the speakerset AND the PC. If the speakerset is NOT connected to the PC you hear any noise? Perhaps try with a MP3 player or so on batteries. I'm thinking of a groundloop problem.

[MartinLiss]

Thank but as I said befor the noise predates the UPS.

[Lord Orwell]

you near any cell towers? Any other source of high-frequency such as a cb antenna? Shortwave? Speakers are notorious for picking up stray signals. I had a set that would sometimes pick up a radio station and play it at a very low volume, even when the computer was off. The speakers did not contain a tuner by the way.

[MartinLiss]

you near any cell towers? Any other source of high-frequency such as a cb antenna? Shortwave? Speakers are notorious for picking up stray signals. I had a set that would sometimes pick up a radio station and play it at a very low volume, even when the computer was off. The speakers did not contain a tuner by the way.

Sorry but I don't know the answers to any of those questions.

[Lord Orwell]

i'm still voting for the cell phone. It goes tap-tap tap-tap tap-tap buzzzzz

[MartinLiss]

I just checked and the nearest tower is .39 miles away and there are several antennas starting at .44 miles away.

[Lord Orwell]

i am suggesting it's picking up your cell phone, not the tower, although the tower is a possibility.

[MartinLiss]

If you really mean my cellphone then that's not it because my wife and I use them very infrequently.

[Lord Orwell]

its just the pattern you listed. it never makes the noise on an outgoing call but we would always walk to our cell phone or reach for it when we heard a nearby speaker making that noise because invariably it was about to ring. Our truck speaker, pc speaker, it didnt matter. It's a common thing with verison/att. You haven't mentioned who you use, but sometimes we heard it when going in/out of signal. It was some kind of carrier sent to the phone. note that it doesnt have to be your phone. Are you across a wall from a neighbor maybe?

[MartinLiss]

I have an iPhone so of course I use AT&T however it only rings maybe twice a month

[Nightwalker83]

i'm still voting for the cell phone. It goes tap-tap tap-tap tap-tap buzzzzz

Yeah, I agree! The speakers on my tv make that buzzing noise whenever we use a cell phone in range of them.

[MartinLiss]

Maybe it's a neighbor's cellphone.

[TheBigB]

Do you have a dataplan with that iPhone?