Flat and cuverd parametric acoustic loudspeakers measured with exponential sine sweeps

Abstract

Parametric Acoustic Loudspeakers (PALs) utilise ultrasounds to generate an audible field thanks to a non-linear effect in air. This phenomenon is difficult to simulate, so an alternative is to rely on prototyping devices and test them experimentally. Several options exist to manufacture a PAL, the flat surface being the most common. However, transducers can also be set on curved surfaces to attain specific effects. In this paper, a set of four prototypes with different transducer dispositions on flat and convex surfaces are constructed and tested in free-field conditions at several distances. A methodology based on the Exponential Sine Sweep is used for this aim, which allows us to obtain their ultrasonic and audible frequency responses simultaneously. The results were compared with those of a single transducer, revealing significant differences between flat and curved PALs attributed to constructive and destructive interference patterns that vary with transducer arrangement.