Hi! I just got this sound sensor (version 1.1) of the groove platform.
Differently from what it has been said in an answer, the silence value is around 0 and not 512.
This means that a sinusoidal waveform (for example, a sinusoidal waveform of 1 kHz) has an average value of 0, which means that negative values are sampled as 0. This fact avoid me to compute the power of a signal.
Tuning the potentiometer only change the gain, but not the offset.