A multidimensional overview for ultrasonic motor driven loudspeaker development

Twelve years of history for the development activity of the ultrasonic motor driven loudspeaker show a multidimensional aspect. Three main axes are geography, frequency, and mechanical impedance. Geography came first since initial conception was in the UK, yet the prototyping was in Japan. The origin was an idea for a stepping motor driven digital loudspeaker that was to address improving abnormalities coming from the fundamental resonant frequency, the so-called ‘‘F0.’’ Consultation revealed the idea was weak but unexpectedly ‘‘ultrasonic motor’’ was recommended. This led the prototyping to be in Japan, where the invention and development of the motor took place. The second is frequency. For audible sound reproduction, inaudible ultrasonic frequency is employed. Although combination of these two regions in frequency is not new for sound reproduction, a couple between the bottom end of the audible sound reproduction and the ultrasonic motor is completely new for this arena. The third is mechanical impedance since convention is low whereas this one is high. Actually, this is the core of the attempt as most abnormalities around ‘‘F0’’ stem from weak mechanical impedance. Other axes also exhibit contrast against conventions such as linearity, controlling, driving, and lifetime of the motor itself, as well as configuration of the sounding mechanism.