Help... my turntable is alive!

Group,
Thanks for all the suggestions. I was playing records last night and again, the noise was gone. I'm now thinking the noise is record specific, or at least some records are a catalyst to the noise occurring. Either way I should point out that the noise is coming from my subwoofers, as I think my main speakers would not produce the noise at any detectable level. So it comes and goes with different records, and I have more work to do in my investigation. Since it doesn't happen on every LP then maybe the problem isn't even with the turntable setup? Lastly I want to say that the noise is very faint and most people would not hear it unless it was pointed out at each occurrence. I'm still trying to get to the bottom of this... will keep you posted.

Dear Cleeds,
Yes you're quite right. It's unlikely the OPs problems would be compounded by this but it's a possibility.
If fact you've inspired me to acquire a spare for my own turntable even though it's not too old.

Back when I had a Linn the oldest belt was about 20 years old! Regular updates meant previous ones would be only 2-5 years old but were routinely discarded by the dealer even though they were fine.
Thanks for that anyway ;)
Bill

If you think that your turntable is dangerous then disarm it!

@koestner 
Just a thought, but have you checked whether the records on which you hear this noise are properly centred? I believe that the cause of your noise could be the eccentric motion of the arm as it navigates an off-centre record.