Non-stationary Signals, Wavelet Analysis And Fitting

With the development of modern science and technology, the ability of human to understand itself is increasingly improved. From 1980's, the techniques of non-stationary signal analysis and processing, which combine with computer signal processing, image analysis and processing, computer graphics and virtual reality, has been a hot topic research and application issue. The processing and analysis of medical data using computer technique has become a new cross subject and got more and more fast noticeable development speed. Among all the investigative branches of medical data, lung sounds analysis is an important research domain. Its research results would undoubtedly promote the application of clinic diagnosis, medical teaching, and so on. At the same time, the significance of the practical application of lung sounds analysis is far beyond medical category.The time-frequency transform plays an important role in sound analysis field. It makes us process sound signal from time domain and frequency domain synchronously. These traditional Fourier transform methods are very useful in studying the character and component of sounds. But as for the non-stationary signal, this tool is not useful because it is a fully time domain or fully frequency domain transform, it cannot provide the frequency information at any local time segment. Contrarily, when analyze a signal using a 8 function, its frequency resolving power is very poor although it has very high time discernment power. It is important to know what the time information corresponding to some frequencies information. For the time change signals, we need these information, but Fourier transform can not satisfy our requirement. So in this dissertation, we'll discuss how to use wavelet and wavelet packet technique, which has been developed recently, to analyze the non-stationary signals in detail.We choose wavelet and wavelet packet because wavelet transform (WT) itself has the character of multiresolution. This character makes it more fit for mankind physiological acoustics model. At the mention of wavelet packet, it is better than those fixed resolution transform such as STFT(Short Time Fourier Transform), for example.