Improvement in the Acoustic Characteristics of the Micro Speaker by Changing Thickness and Foaming Ratio of the Diaphragm

Abstract:

The typical speaker for cellular phone is composed of magnet, coil, base-film and diaphragm with a structure that laminated a foam sheet and aluminum sheets. A heterogeneous foam sheet which has an uneven elastic modulus was used for a conventional diaphragm, and it reduced an acoustic performance of a conventional speaker. Recently a homogeneous and thin foam sheet was newly developed. The purpose of this study is to improve the acoustic characteristics of the micro speaker by changing thickness and foaming ratio of the newly developed foam sheet. Frequency characteristics and sound pressure level (SPL) were measured by changing foaming ratio of the foam sheet from 2.5 to 5.0 and thickness of the foam sheet from 0.15 mm to 0.30 mm. To clarify the relationship between the design parameter of foam sheet and the frequency characteristics of the micro speaker, natural frequency analysis using finite element method (FEM) was performed. The result of FEM analysis was also compared with the experimental result using a laser doppler velocimetry sensor. It was found that the widest reproducible frequency range was obtained when the foam sheet was used 0.30 mm of thickness and 5.0 of foaming ratio. The reproducible frequency range spread out 15% in comparison with that of a conventional micro speaker.

• Periodical: Advanced Materials Research (Volumes 718-720)
• Pages: 1310-1315
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.718-720.1310
• Online since: July 2013
• Authors: Takeshi Nomoto, Takeru Moriuchi, Toru Fujii
• Keywords: Finite Element Method (FEM), Foam Sheet, Micro Speaker, Speaker Diaphragm

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