Audio Systems: Speaker issue, commercial radio stations, walkie talkies

Question
QUESTION: Hi, I am working on fixing an in-ceiling speaker system for a country club. The problem that they have run into is an incredible amount of noise/static coming from the speakers when they are turned on and the volume is brought up to an acceptable level. This occurs without having any audio running through. Just the master volume up at unity. Now the only thing I can think of is that the amps powering the speakers are either turned down too low or simply not powerful enough. Is there any other possible explanation?

Thanks

ANSWER: Hi Marc,

Noise can be especially difficult to troubleshoot because virtually EVERYTHING produces some noise.  So, rather than take a guess, I'll list everything I know of that could cause noise/static in a system of this type (I've listed it in order from most likely to least likely):
- Low quality speakers/wires/amplifier (a lot of cheaper equipment hisses simply because they didn't shield it properly when it was made)
- Unbalanced connections (a lot of systems use unbalanced connections; a balanced connection type will cancel out noise; see http://www.equitech.com/support/wiring.html)
- Noisy electrical components in the amplifier. A lot of older amplifiers hiss. A lot.  You can't really do much about it except replace the amplifier.
- The amps powering the speakers may be turned up too high relative to the main system power. If there is a "main system" of some sort that sends out a weak signal to speakers (and if those speakers have separate amplifiers), then the amplifiers in each speaker could be to blame. But, if you turn up the main volume, and turn down the volume of each speaker, the noise should decrease.
- Ground loop / improper grounding (make sure everything is attached to the same ground; see http://www.epanorama.net/documents/groundloop/index.html)
- EM or other interference (cell phones, walkie-talkies, commercial radio stations, HVAC systems)

Hope this helps!


---------- FOLLOW-UP ----------

QUESTION: Thank you very much. I forgot to add that they are using a pretty old wireless mic system. Could that also be one of the causes?

Answer
It very well could be... try unplugging it and see if the noise goes away.  In this case, noise caused by a wireless microphone system could fall into the category of unbalanced connections, noisy electrical interference, or EM interference.  

Also worth mentioning is that as soon as the transition to digital TV is complete, the radio spectrum currently allocated to older VHF microphone systems will be auctioned off, and VHF wireless microphones will not work reliably.  It might be worth it to them to consider upgrading their microphones to UHF at the least, and upgrading the entire system would be ideal.