Parametric loudspeaker: From theory to applications

A review of the current state of parametric loudspeaker from the aspects of modelling, measurement, signal processing, implementation and applications is presented in this paper. A variety of well-established and emerging numerical methods to predict the propagation of finite amplitude sound beams are discussed and compared. The accurate measurement of the difference-frequency sound is another research interest related to parametric loudspeaker. The measurement methods using an acoustic filter are outlined, and the approaches by taking advantage of condenser microphone sensitivity characteristics or phase cancelling technique are also shown. The signal processing algorithm to reduce the harmful effects of the harmonic distortion also has constantly attracted the attention of researchers. The processing method based on Berktay's solution together with the new approaches using psychoacoustic phenomenon or Volterra filter modelling are given. Furthermore, the detailed implementation of parametric loudspeaker is summarized and its potential application is listed. This paper will focus on the recent advance in the parametric loudspeaker field from theoretical perspective as well as engineering perspective to promote the theoretical and practical development of the parametric loudspeaker.