Another complication to note is that pitch != frequency. Pitch is how we perceive the thing. The same frequency at different volumes can be perceived as diffe

Another complication to note is that pitch != frequency. Pitch is how we perceive the thing. The same frequency at different volumes can be perceived as different pitches. So you really can't ever find perfect without knowing some exact context. See wikipedia entry on pitch perception for more examples: http://en.wikipedia.org/wiki/Pitch_(music)#Perception_of_pitch