The equivalent fluctuating area for modelling harmonic acoustic pneumatic sources (HAPS)

Abstract

This paper presents a physical model of a new type of electropneumatic sound source, the harmonic acoustic pneumatic source (HAPS). This theory allows to model an HAPS, more complex than classical electropneumatic sources and to determine in details the characteristics of the generated pressure wave, including its phase. To that end, an electropneumatic sound source, composed of a fixed area in line with a fluctuating area, is reduced to its equivalent time varying area. It can then be considered as a pressure source with an internal impedance embedded in a classical transmission line model. Amplitudes and phases are predicted using this analytical model and compared to those obtained using numerical simulations. Each of the parameters having an influence on the source characteristics is varied over a wide range to determine their impact on the acoustic wave. An experimental investigation is then performed on an existing HAPS prototype. The comparison between numerical, analytical and experimental results shows that an electropneumatic sound source no longer has to be limited to a unique fluctuating area to be accurately modeled. Such a simple model is foreseen to be a tool to design new electropneumatic sound sources.