Mac Mini making strange noises through external speakers

Question

I am experiencing a strange problem with my mac mini and my external speakers. I have two different sets of speakers and the problem occurs with both so I don't think its the speakers as I have never had any problems with them on my other computers. The Mini will make strange gurgling and hissing noises through the speakers at seemingly idle cpu times. Under heavy loads I get the gurgle occasionally but it seems more prevalent at idle times. After playing around with it I have noticed a direct correlation with my wireless connection and the noise. If the mini drops the network, which it does from time to time, I get the noises but if I disable airport then they stop. Have any other mini users experienced this? It's harmless but rather annoying because my mini is set up in my dorm room and we often have music playing and when I go to sleep I hear these weird noises.
Thanks for the feedback in advance.

Answer 1

The Airport sub-system in the mini is identical to any other Airport Extreme equipped Mac, with the addition of a riser board on which the AE card is mounted, and which no other Mac has.
If the mini suffered a design flaw in Airport implementation, then everyone would be hearing the same sound. Neither AE-eqipped minis I've got in my system exhibit any sign of it.
RF interference can get into an audio system in a number of ways - most commonly by direct injection (ie, something in the audio circuit such as a circuit board track or speaker wire) acting as an antenna and picking up an unwanted signal, or by FR breakthrough into the power circuit - usually through the transformer or rectifiers. In the first instance, a change in channel would change the transmission frequency and thus the sensitivity of the component to the signal (thus usually making it stop altogether) and in the second, would usually require a transmission power of significantly higher level than the few milliwatts used by Airport.
There are other possible causes too of course. Even a cordless phone in the same vicinity is capable of generating RF interference - but then stories of people listening to radio stations breaking through into phone lines, and even when opening oven doors are legion - and often true.
In the case of an Airport network, where the user has control over transmission power levels and frequency, a bit of tinkering with the two can resolve many FR interference issues. Incidentally, if you're interested (given your general technical background) a number of very informative sources on RFI (Radio Frequency Interference) are published for and by the amateur radio fraternity.