Transducer research at bell laboratories under manfred schroeder

Abstract

In this chapter, the work on electroacoustic transducers and the corresponding materials research in Manfred Schroeder’s Department at Bell Laboratories is reviewed, together with ensuing work at other laboratories. The emphasis is on studies of electret-type transducers and materials. This includes the description of the first polymer electret microphone, the first use of fluorocarbon electrets of high thermal stability soon thereafter, and the introduction of directional electret microphones. Other electret transducers designed during this period, such as microphone arrays, headphones, and touch actuators, are also discussed. Next, early materials research on polymer electrets at Bell Labs, utilizing isothermal and thermally stimulated methods as well as electron radiation experiments, is reviewed. Finally, the later studies in a number of other laboratories, based on the early work under Schroeder, are outlined. This includes, among others, research on digital electret headphones, two-dimensional arrays, silicon (MEMS) condenser microphones, and, extending into the present time, transducers based on piezoelectric cellular polymers.