如何用数字信号处理的方法祛除噪声？？

这里给出一个例子，你可以参考一下。

% Read in audio file, here extension of mp3.[wave_raw, fs] = audioread( '144.mp3' );dn = length(wave_raw);dt = 1 / fs;t = (0: 1: dn-1) * dt;% Do fft on raw audio data.f = (0: 1: dn-1) * fs / dn;fft_raw = abs(fft(wave_raw));% Band-pass filtering on raw data.f1 = 1e3; f2 = 2e3;[b,a] = butter(4, [2*f1/fs, 2*f2/fs],'bandpass');freqz(b, a);wave_filt = filter(b, a, wave_raw); % Do fft on filtered audio data.fft_filt = abs(fft(wave_filt));% Visualization.figure(1);subplot(2, 2, 1);plot(t, wave_raw);xlabel('Time (s)');ylabel('Amp.');title('Raw audio wave');set(gca, 'fontsize', 20);hold on;subplot(2, 2, 2);plot(f/1e3, fft_raw);xlim([0, 5])xlabel('Frequency (kHz)')ylabel('Amp.');title('Amp. Spectra of raw data');set(gca, 'fontsize', 20);hold on;subplot(2, 2, 3)plot(t, wave_filt);xlabel('Time (s)');ylabel('Amp.');title('Filtered audio wave');set(gca, 'fontsize', 20);subplot(2, 2, 4);plot(f/1e3, fft_filt);xlim([0, 5]);xlabel('Frequency (kHz)')ylabel('Amp.');title('Amp. Spectra of filtered data');set(gca, 'fontsize', 20);最后画图比较一下滤波前后的语音波形图及其振幅谱图，