Distributed Transducer
Martin Greenspan, Raymond M. Wilmotte · The Journal of the Acoustical Society of America · 1958
The distributed transducer is an array of transducers separated by inactive material having their common characteristic impedance, Z0, and terminated in Z0 at one (the absorber) end. The other end radiates into a load. The input voltages at the successive inputs are delayed so that the speed of the electrical wave, traveling in the direction absorber to load, equals the speed of sound in the transducer material. The elements may or may not be identical and they may or may not be operated near resonance; the acoustic waves arrive at the load in phase in any case. A great variety of frequency-response characteristics is readily synthesized; particular attention is paid to a flat response over a very broad range. At the same time, the response at the absorber is subject to some control so that the power there dissipated can be minimized.