A Mechanism for Obtaining Damping Material with a Uniform, Prescribed Acoustic Impedance

One of the problems involved in controlling the response of a transducer is that of obtaining damping material with a given acoustic impedance. In the past, the difficulty encountered has not only been that of procuring material with certain desired acoustic properties, but also that of obtaining quantities of material with these properties. A mechanism has been devised which can calender a thermo-plastic material such as Nylon, Orlon, etc., to obtain a wide range of acoustic impedances. This mechanism has three variables: heat, pressure, and speed. These variables are manipulated until the acoustic impedance of the cloth, as measured with a calibrated detector, falls within the calculated limits necessary to obtain the desired response of the transducer. The mechanism combines the processes of calendering and acoustic-impedance measurement and the result is a damping material with a uniform, prescribed acoustic impedance.