A MEMS apparatus is provided for scanning an optical beam which comprises: a. at least one mirror operative to perform am oscillation motion to a pre-defined rotation angle around a mirror rotation axis; b. a sound sensing means; and c. a conversion means operative to convert sound vibrations detected by the sound sensing means into one or more electrical signals, and wherein the sound sensing means is located at the vicinity of the at least one mirror whereby the movement of the at least one mirror is sensed by the sound sensing means and converted by the conversion means into the one or more electrical signals characterizing the oscillating motion of the at least one mirror.