MEASUREMENT OF THE REVERBERATION TIME IN ROOM ACOUSTICS USING AN OMNIDIRECTIONAL PARAMETRIC LOUDSPEAKER AND EXPONENTIAL SINE SWEEPS

An omnidirectional parametric loudspeaker (OPL) is a sound source that relies on the parametric acoustic array (PAA) phenomenon to generate an omnidirectional sound field. It consists of hundreds of ultrasound transducers set on a sphere surface, each one emitting an ultrasonic collimated beam consisting of an audible signal modulated in amplitude. The air itself demodulates this signal thanks to the PAA phenomenon, bringing it back to the audible range. This results in hundreds of sound beams emitted in all directions. The OPL was designed for room acoustic measurements, but its performance in this field has not been examined yet. The aim of this work is to take the first steps in this direction by developing a methodology for measuring the reverberation time of rooms using the OPL. Exponential sine sweeps (ESS) will be used for this purpose, since they allow the OPL to focus all the emitted power in a single frequency as compared to broadband excitation signals such as white noise. This results in higher ultrasonic power levels and thus in higher audible sound pressure levels, increasing in this way the signal to noise ratio. The OPL measured reverberation times are compared with those obtained with a commercial dodecahedron loudspeaker.