My guess is that your UPS has AVR, or Automatic Voltage Regulation. This kicks in when the voltage coming through your mains is lower or higher than a certain amount. When this occurs, you will hear a buzzing noise created by a relay switching off and on. Now, about the fan, I don't know. As far as ...

I agree with what sthayashi said. Also, flouresecent lights can cause hum. And, you might try moving your subwoofer away from the back wall a bit. That might help. Most of the built-in amplifiers in these subwoofers are PWM, or pulse width modulating, amplifiers. That is essentially what computers d...

Logitech dinNovo cordless desktop is the model that might do the trick for you.

Regards,

Rusk

I agree with hvengel that the subwoofer might be interacting with your house wiring and could be picking up AM signals that are in the wiring. Glad to hear that it has gotten a lot better and hope that you resolve the remainder of the noise coming out of your speakers.

Regards,

As I was reading through this I was wondering if it might be the subwoofer. Finally, I got to your post where you said it was the subwoofer. I believe that what is happening is that the power supply and the amplifier in your subwoofer are working together to pick up the radio signals. These subwoofe...