In order to optimize turbocharger control, this work presents a methodology that allows extracting information about turbocharger operating conditions through a proper processing of the signal coming from one accelerometer mounted on the compressor diffuser or a microphone facing the turbocharger. In particular, the developed methodology is suitable for the estimation of both turbocharger rotational speed (mean value)and the amplitude of its instantaneous oscillations. Then, such oscillations can be used as an indicator of power delivered by the turbine. The whole methodology has been developed for a 4-cylinder Common-Rail light-duty Diesel engine installed in a test cell at the University of Bologna. Many works, carried out over the past years, demonstrate that turbocharger speed can be estimated through a proper processing of vibration [4] or acoustic emission signals [5].