New methods for parameterization of Distributed Mode Loudspeakers

Distributed Mode Loudspeakers (DMLs) operate by bending oscillations of a plate with specifically designed dimensions and stiffness. They exhibit specific transfer functions, which need to be described with a series of amplitude-frequency characteristics measured at points located across a measurement hemisphere. The measurement results of the same transducer, taken at closely spaced points, can significantly differ from each other. The aim of this work was to develop numerical parameters that qualitatively describe the amplitude-frequency characteristics of a DML measured at individual points. These parameters, plotted in a way showing their relation to directions, are intended to identify the directions where the radiation of a DML exhibits properties closest to desired ones. The formulated quantities are based on a parameterization model developed for conventional pistonic loudspeakers, specifically relating to the flatness of amplitude responses, for which the correlation with listener preferences has been observed.