Vibration and noise spectra from automotive planetary transmissions commonly exhibit components at distinct frequencies around the gear mesh (tooth passing) frequency and its higher harmonics, called modulation sidebands. They constitute a significant portion of the vibration and noise generated by the transmission. Sidebands have influence on noise quality measures as well as having great potential to provide valuable clues in regards to gear tooth combinations, phasing of planets, manufacturing errors like eccentricity, run out present in the gear set. First critical step in designing and controlling the sideband activity of a planetary transmission is to develop a comprehensive model to predict modulation sidebands as well as describing the mechanisms causing sidebands. The paper describes the investigation of side bands, correlation with theoretical, analytical and test results and solution to minimize the noise. The paper also describes the importance in selecting the number of planets and tooth numbers while designing the planetary system for NVH perspective.