Abstract
In this work, a polyvinylidene fluoride (PVDF) loudspeaker is developed for mobile devices, where thickness and efficiency is of chief concern. The membrane is slightly curved to convert in-plane strains to transverse motions. To facilitate the design optimization, a simulation platform is established by using a hybrid analogous circuit. While the circuit is primarily lumped-parameter in nature, the mechanical impedance is derived from finite-element analysis. This enables the prediction of the high order modes of the loudspeaker. Simulation result indicates that a reduced radius of curvature leads to increased sound pressure level and a higher resonance frequency. To identify the lumped parameters, a special procedure is developed. Based on the measurement of electrical impedance, the electrical capacitance is estimated. Mechanical parameters and coupling factor are identified from the measurement of diaphragm velocity with a laser vibrometer inside a vacuum chamber. To optimize the design parameters of the loudspeaker, the simulated annealing (SA) algorithm is used under practical constraints. The results have shown that, with the optimal configuration, the sound pressure level is increased by 15 dB and the resonance frequency is increased by 700 Hz, as compared with a non-optimal design. Copyright© (2013) by Austrian Noise Abatement Association (OAL).