A HELMHOLTZ RESONATOR MODEL FOR AN ELECTROSTATIC ULTRASONIC AIR TRANSDUCER WITH A V-GROOVED BACKPLATE

A model for the resonance frequency of an electrostatic ultrasonic air transducer with a uniformly grooved backplate is described based on the Helmholtz resonator theory. The resonance frequency of the transducer can be determined from the shape and dimensions of the backplate's grooves and the membrane's characteristics. In the case of a V-grooved backplate, the depth of the groove and the mass per unit area of the membrane are the parameters that determinate the resonance frequency. Experimental results suggest that the tension of the membrane seems to have only a very weak influence on the resonance frequency.