my TiBook gently purrs (Score 1)

Late at night when it's very very quiet, my TiBook makes a barely audible noise that sounds like a quiet cat purr, which I must admit is somewhat endearing. As I move windows the purr becomes slightly more granular, but still not unpleasant. I've come to think of it as an added "feature."

A very low tech ear-to-speaker auditory location test has revealed that the noise is indeed coming from my speakers