Optimal Implementation of Miniature Piezoelectric Panel Speakers Using the Taguchi Method and Genetic Algorithm

TLDR: In this paper, a thin and miniature piezoelectric panel speaker has been developed using the energy method in conjunction with the finite element method, where the electrical system, mechanical system and acoustic loading are considered in combined fashion.

Abstract: A thin and miniature piezoelectric panel speaker has been developed in this paper. The system is modeled using the energy method in conjunction with the finite element method. The electrical system, mechanical system and acoustic loading are considered in combined fashion. The genetic algorithm (GA) and the Taguchi method are employed to achieve optimal designs with low fundamental frequency and high acoustic output. The designs resulting from the optimization are then implemented and evaluated by experiments. These experiments were carried out on the basis of quantitative and subjective performance measures. The experimental results indicate that the piezoelectric panel speakers are capable of producing comparable acoustic output with significantly less electrical power than the conventional voice-coil panel speakers. @DOI: 10.1115/1.1759695# The 3C industry ~Computer, Communication, and Consumer! has recently emerged as one of the most rapidly growing industries of modern days. Commercial products such as personal data assistants ~PDAs!, mobile phones, MP3 players are currently making their way into the market and everyone’s life. From the design point of view, one of the chief concerns of 3C products is miniaturization. This is particularly true for the loudspeaker that is an important component of 3C products. Panel speakers provide a potential solution to meet the requirement of miniaturization @1#. Apart from small size, panel speakers also offer advantages of omni-directional radiation, linearity, insensitivity to room boundary condition and bi-polar radiation @2#. A detailed analysis of the panel speaker can be found in @1#. Despite all the advantages, panel speakers suffer from two drawbacks that limit their use in practical 3C applications. First, the exciter for a panel speaker is traditionally the voice-coil type and could reach only approximately 2 mm thickness, which is still too thick to apply in many 3C products such as mobile phones. Second, the electro-acoustic efficiency driven by the voice-coil exciters was found to be quite low @1#, which presents problem of power consumption to mobile electronic products. These physical limitations associated with the conventional voice-coil exciters hence motivate the present development of an alternative way of excitation for panel speakers. In this paper, panel speakers excited by piezoelectric ceramics are proposed, in an attempt to overcome the problems encountered in voice-coil exciters @3#. Relatively high efficiency of piezoelectric material makes the piezoelectric panel speaker an ideal device for many battery-powered products. Although the piezoelectric panel speakers have been around for some time, these devices mainly exist in the forms of narrowband acoustic radiators such as buzzers, sounders, sirens, etc., where sound quality is generally not of the major concern. By contrast, this work seeks to meet the requirements of quality loudspeakers for speech and music rendering. To this end, optimization techniques are utilized to achieve practical designs with minimum fundamental frequency and the maximum sound pressure output. This paper is organized as follows. First, the dynamic model of the piezoelectric speaker was derived using the energy method and the finite element method~FEM!. Unlike Ref. @1#, the electrical system, mechanical system and acoustic loading are considered as a coupled system during dynamic modeling. This is important for a light structure like a panel speaker, especially for low frequencies where acoustic mass loading is not negligible. Second, the Taguchi method and the genetic algorithm ~GA! are employed to optimize the speaker design. The Taguchi method is used for a preliminary search, whereas the GA is used to ‘‘fine tune’’ the design parameters. Designs resulting from the optimization are then implemented and evaluated experimentally. In order to evaluate the speaker performance, quantitative measures as well as subjective indices are measured and summarized.