weird pop noise from computer

The past month or so my computer has been making a weird popping noise that is relatively soft and with a bit of a splurt, for lack of a better word, noise also. It's a really short noise that sounds similar to the Facebook chat noise, but not as poppy as that.

I've noticed it seems to happen when my computer hasn't made any noise for a while (because I've been doing something that doesn't require noise) and then when it needs to make noise, the weird pop noise happens first before the desired noise. For example, if I sit here and don't do anything but type this post for about a minute, then hit the volume up key, there is the quiet popping/weird noise then the normal chirp noise. It also seems to happen at random times...??

This actually happened on my friend's brand new macbook first, then it started happening on my computer (MacBook Pro from March).

Does anyone know anything that might explain this/anything I could do to stop it?

Thanks

 

I got it in March '08 with Leopard on it. It's a 2.4 Ghz, got it right before the Multi Touch trackpads came with them (sadly)...

If I plug in earphones it doesn't make the sound, but I can hear a background kind of static sound when the computer need to make noise, and then that stops after about 30 seconds. When that stops and I hit volume up or something there is a bit of a delay where the pop noise would be and then the chirp, and then background static for 30 seconds.

It also happened on the new MacBook too though... ?

 

So I finally got around to doing a SMC and PRAM reset and it still makes the noise. Even after doing the PRAM reset (second), when the computer made the second startup noise there was the little pop noise right before the startup noise.

So the "pop" noise is still happening, even when I turn the computer on and after any amount of time I've been on it...

hmm.

 

Ok, thank you very much for the info! I'll pass it onto my friend...