檢測揚聲器優劣之分析與實驗方法

Abstract

本文目的在於提出非接觸的揚聲器檢測裝置，在一個中空的箱體下方裝載待測揚聲器、上方裝載一個平板，並且給予待測揚聲器正弦波激振力，聲壓經由箱體內空氣傳遞到上方平板。當檢測上方平板的時間-響應圖為非正弦波，或是頻率-響應圖在除了激振頻率及倍數頻率之外出現峰值，即可判斷揚聲器含有雜音，並且透過有限元素軟體ANSYS來預測實驗結果。另外，此檢測裝置亦可驗證 待測物的材料常數，經由頻率-響應圖得到實驗值，與理論值比較後可以判斷待測物是否變質。

The purpose of the thesis is to study the behavior of imperfect panel-form speakers. A nondestructive detection device is developed for the study of speaker imperfections. The device consists of two parts, namely, upper and lower parts, which are connected by an empty box. The lower part houses the speaker for testing while the upper part a plate suspended by a surround. The speaker is excited by a harmonic load and the sound radiated from the speaker will propagate through the empty box and excite the upper plate. The response of the upper plate is measured via an accelerometer or a laser vibro-meter. Speakers with imperfections are detected from the measured frequency response functions and time response functions of the upper plate. If the measured time response function of the upper plate is not a sine wave or the frequency response function has additional frequencies except the excitation frequency, then the speaker has some kind of imperfections. The finite element software ANSYS is also used to predict the response of the upper plate to validate the suitability of the detection device. Besides, based on frequency response function, we demonstrate that the material constants can also be determined from the measured data using the proposed device.