"DIMENSION

DIME represents 10. Remove the middle letter 'N' and the first 3 letters, and read backwards and you have NOISE, a kind of sound. Space is usually in 3 dimensions. Others include Time, the 'Fourth Dimension', as a dimension of space. There is also the 5th Dimension, a 60's music group."

I went ahead and accepted DIMENSIONS as well, since the "there are 3 of me, 4 if you include time" part really only works in the plural. This problem was way too easy for you puzzle nuts, as you'll see from the statistics below.

Winner: gorky

Contest Statistics: Newsletter sent to 298369 subscribers, 79 answers submitted, 78 answers correct, 98.73% accuracy. Chance of a correct answer winning: 1.28%.