曲面壓電薄膜揚聲器之頻域響應 與低頻探討

Abstract

本研究目的為探討曲面壓電薄膜PVDF在可聽頻段之適用頻寬與將頻寬往低頻延伸之可行性。研究主要透過數值模擬觀察PVDF薄膜之頻率響應。確立數值模擬結果之準確性後，以數值模型做參數分析，包括曲率、振動面積、厚度、幾何形狀、薄膜多曲率、彎曲方向以及積層薄膜。曲率因素能使基本共振頻率改變，藉以調整PVDF揚聲器適用頻寬。加大振動面積或減少厚度可以使其音量增大。而幾何形狀並不影響基本共振頻率與聲壓位準值。同時我們也發現PVDF有曲率敏感之特性，稍有一點不同曲率在PVDF薄膜上，便會有不同的頻域特性。此外彎曲方向須一致，若不一致會使發聲效果下降。改變積層數目也能使音量增大，但會使SPL曲線不平坦。綜合以上參數分析便可設計出適合不同需求之曲面壓電薄膜揚聲器。

This study aims to investigate the bandwidth of PVDF in the audible frequency and the feasibility of fine acoustic performance at low frequency. The frequency response of PVDF film was observed by numerical simulation. After determining the accuracy of the numerical simulation results, the numerical model is used to the parametric analysis, including curvature, vibration area, thickness, geometry, multi-curvature, bending direction and multi-layers. Curvature can make the fundamental resonant frequency change, in order to adjust the PVDF speaker bandwidth. Increasing the vibration area or reducing the thickness can increase the volume. And the geometric shape does not affect the fundamental resonance frequency and sound pressure level value. At the same time we also found that PVDF has a curvature-sensitive characteristics, slightly different curvature in the PVDF film, there will be different frequency domain characteristics. In addition, bending direction should be the same, or make the acoustic radiation effect down. Changing the number of layers also increases the volume, but makes the SPL curve uneven. According to the above parametric analysis, we can design different curved piezoelectric film speaker for our needs.