非線性係數及非線性特性在稍早之研究中均以頻域分析方法為主導，本研究以時頻域分析方法，探討此非線性係數及特性，在不同分析方法下之適用性。傳統訊號分析法不外乎是快速傅立葉轉換，但要處理的訊號是非平穩訊號時，需使用時頻分析的方法，以同時得知訊號時間和頻率的資訊。因此本文中使用小波轉換來分析聲波之非線性訊號，並比較各方法分析之結果及適用性。本研究之目的在於希望以各種時頻域分析方法去對聲波的非線性現象作分析，探討在各種訊號分析方法下，多少週期之聲音脈衝發射波( tone burst ) ，才能準確的預估非線性係數及非線性特性。

We applied the frequency analysis for nonlinear coefficient and properties early in the study. The time – frequency analysis is applied for nonlinear coefficient and properties in this study. We will discuss the results for different time – frequency analysis methods. The fast Fourier transform is a traditional way to analyze the signal. But when we handle the nonstationary signal, we need the time – frequency analysis for obtaining the time information and frequency information from the signal simultaneously. We use the wavelet transform to analyze the nonlinear signal of the tone burst. We then compare the results with different time – frequency analyses. The purpose of the study is to analyze the acoustics nonlinear properties by different time – frequency analyses. We will use several signal processing to provide examples of how many cycles tone burst can exactly predict the nonlinear coefficient and properties.

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