I recently spoke with an audio engineer (my Dad, who has worked in radio for many years) about something that's been bugging me for many years: Why do almost all computer speakers have some sort of annoying buzz or hum?
I know it has to do with voltage differences, power, RF emissions, etc... but I wanted to know more about what I could try to do to reduce the level of the noise. I've tried things like plugging everything into one outlet/power strip, using a filtered power adapter, using a ground loop reduction magnet, etc., with varying degrees of success.
60hz buzz in a speaker is typically induced in the power lead. If that is the case, the buzz will be in the speakers even if the audio connections are removed.
If the buzz is there with audio input to speakers is disconnected, the problem is the AC adapter, the actual power supply (from your mains), or the amplifier for the speakers (usually, for computer speakers, these are in one of the speakers or inside the subwoofer).
If the buzz starts when a wire is connected it can be a few things. One is a high level of energy in the surrounding air - like a MRI machine would do or possibly a wireless device. Another is a bad ground connection somewhere - like a bad audio cable. Change the cable. If you can't do that, wiggle it a lot and move it around and see if there is a difference.
(Note: At my current residence, I'm less than a mile from no less than three radio towers, with more than 15 radio stations' antenna broadcasting at thousands of watts each... many computer speakers are unable to cope with that amount of RF, as shielding on computer speaker cables is notoriously weak or not present at all).
The last thing to look at is the voltage difference between the audio output device (computer) and the input device (amplifier in the speakers). The first thing to try is rotate the power plug on just one of the devices. The second is to try and run a separate grounding wire between the two - finding a nice grounded spot on both. Third try is running a ground wire to each device from a good ground like a water pipe that goes to the outside.
Another simple test is to short the inputs on the speakers — if there is more than one short the one not in use.
The best solution is often to shell out a few more dollars for some better speakers. I've used more than 10 different speaker sets in the past 15 years, and I've settled on the Bose Companion 2 Series II speakers, as they are pretty compact, and put out great, almost noise-less sound, without a large footprint. For a long time, I suffered through a bunch of cheaper Creative, Altec-Lansing, etc. speakers, all with similar problems (one set of speakers tuned in quite clearly to 94.7 FM!).
I figure I have a 700W 5.1 sound system with some nice, big JBL and Sony speakers in my main room, and if I need some really pure sound, I'll work from the room with that setup instead :)
See related: Buzz or Hum with a Logitech USB Headset.