Radar based loudspeaker measurements

In this paper a new approach to loudspeaker analysis and measurements is introduced. The theory on which it's based is called radar micro-Doppler analysis; it offers some potential benefits over traditional test methods to characterise the mechanical motion of a transducer, and it is well suited to identify design issues while in the research phase, or to deploy efficient end-of-line tests. This because, compared to acoustic based approaches, the use of a radar allows reliable sensing in an acoustically impaired environment, such as a production line. In addition, when compared with a laser vibrometric method the use of radar micro-Doppler reduces the number of measurements required and provides direct access to the information of the metallic components of the loudspeaker. After a brief summary of the theory, this article will show promising experimental results and analysis of the micro-Doppler signatures of a woofer achieved using a low cost radar system. Based on Thiele&Small parameters, the voice coil displacement is modelled and micro-Doppler signatures for a single tone and a sine sweep stimulus are presented. Furthermore, in order to characterise the speaker with a single radar measurement, a methodology to gather the mechanical frequency response of loudspeakers is also shown.