Speaker is the converting device which change electric energy to sound energy, and we can easily see the speaker. They are widely used to home and car audio unit, home and industrial alarm device. Sometimes, the alarm sounds cause the environmental noise. Therefore it is important to design the appropriate speaker according to the installed device and position. In order to study the vibration and sound characteristics, the curvature of the cone paper is changed. Finite element method is used to compute the vibration characteristics and mode. Indoor and Vehicle teats are carried out to investigate the non-linear characteristics and the sound characteristics for some car speakers.

Most of speakers, the con-paper (con shape) or vibration plate generate the sound by reciprocating motion which is received vibrating signal from voice coil. On the other hand, the vibration speaker that reproduces sound by attaching a vibration head to some materials such as wood, plastic, glass plate, etc. instead of cone paper or vibration plate generates different sound timbres depending on the attached materials with vibration head. so we can hear a variety of timbres than ordinary speakers. In this study, the characteristics of vibration and sound propagation according to various materials attached to the vibration head of the vibration speaker were experimentally investigated and this sound propagation characteristics were compare with woofer speaker and micro speaker. As a result of sound propagation characteristics of vibration speaker, the reproduction ability of low frequency band wes inferior to compared than woofer speaker and micro speaker. This is judged to be due to the material characteristics of glass and wood which are source of the sound propagation. As compare with 1kHz sine tone, the woofer speaker has not generated the high order harmonic component, but the glass plate and wood plate used with the vibration speaker head have generated the high order harmonic component at a level that can not be ignored. According to above results, the vibration speaker will be had a low articulation of sound because the higher volume to generate the high distortion.

The loudspeaker is the directly radiated speaker which generates the sound by the vibration of cone paper. Therefore the shape and the vibration characteristics of th cone paper is important factors affecting the performance of speaker. The vibration mode of cone paper is piston mode that vibrates to the up-down direction, and we can see the divided vibration in the higher mode. Because the loudspeaker has a damper, the vibration mode is different to the mode of the only cone paper. In this study, the vibration mode of cone paper which considering the damper and the effects of the damper diameter were investigated by finite element method

Micro speakers are used to reproduce sound in small electric and information and communications devices, such as cellular phones, PMPs, and MP3 players. The acoustical properties and sound quality, which are changed due to the decreased size of the speaker, are often adjusted varying the type and thickness of the diaphragm. The most widely used diaphragm material is thin polymer. It was previously reported by the author of this paper that the resonance frequency of a micro speaker is changed by the type and thickness of a polymer diaphragm. In this paper, the frequency response near the resonance frequency of a micro speaker was studied as functions of the type and thickness of the polymer diaphragm. While Rmax and RDC were affected by the type and thickness, an analysis of the electrical impedance curve revealed that Ro(= Rmax/RDC) and δf were not changed. Thus, QTS which was function of Ro, δf, and the resonance frequency, is only related to the resonance frequency. The increase of the resonance frequency led to a proportional rise of QTS. The change of the frequency response near the resonance frequency was not dependent on the type or thickness of the polymer diaphragm, but was affected by the resonance frequency.

Information technology devices, such as cellular phones, MP3s and so on, due to restrictions of space, require thin and small micro-speakers to generate sound. The reduction of the size of micro-speakers has resulted in the decrease of sound quality, due to such factors as frequency range and sound pressure level. In this study, the acoustical properties of oval microspeakers has been studied as a function of pattern shape on the diaphragm. The other conditions of micro-speakers, except for the pattern, was not changed. When the pattern is present on the diaphragm and the shape of pattern was a whirlwind, the resonance frequency was reduced due to the decrease of tensile strength of diaphragm. The patterns presented in the semi-minor axis of diaphragm did not effect a change of resonance frequency. However, increasing the number of patterns in the semimajor axis of diaphragm became a reason for the decrease of resonance frequency on edge side. When the depth of pattern on edge side was increased, the resonance frequency was decreased due to reduction of geometrical stiffness. If the height of edge and dome were increased, the resonance frequency and geometrical stiffness rapidly increased. After reaching the maximum values, they began to decrease with the continuous increase of height.