Reaction effects in piezoelectric plastic film transducers for earphones

Abstract

The author has recently reported a theory of a domed piezoelectric plastic film which can be used as a combined diaphragm and transducer element in an earphone (see ibid., vol.13, p.201, 1980). This paper describes some modifications to the theory which may be necessary when the diaphragm is actually used in the device. In practical earphones the diaphragm displacement may be influenced by reaction effects of the sound pressure generated. At sufficiently low frequencies the reaction effect is easily incorporated into the earlier theory and criteria are derived for when it becomes important. The sound pressure is then calculated for the limiting cases where the reaction effect is either dominant or negligible.