巴特沃斯濾波器 python

Question

我想用巴特沃斯帶通過濾一個wav文件。 我嘗試將wav文件轉換為fft然后應用帶通濾波器，然后應用ifft 。 從圖形上看，它似乎被過濾了一點，但是當我減少輸入和 output wav時，音頻沒有區別，就像過濾器一樣，它不起作用。 有錯誤嗎？

# FFT - Fast Fourier Transform
frequency,data = wavfile.read('Input_sound.wav')
signalFFT = fft(data)
def butter_bandpass_filter(data, lowcut, highcut, frequency, order):
    nyq = 0.5 * frequency
    low = lowcut / nyq
    high = highcut / nyq

    b, a = butter(order, [low, high], btype='bandpass')
    y = lfilter(b, a, data)
    return y 
funct=butter_bandpass_filter(signalFFT,2100,3400,44100,4)

filtered_sound=ifft(funct)
filtered_sound=sp.real(filtered_sound)
filtered_sound=sp.int16(filtered_sound/sp.absolute(filtered_sound).max()*32767)
wavfile.write('Filtered_ouput.wav',frequency,filtered_sound)

Answer 1

看lfilter 文檔的example，好像不需要進行FFT，直接把data提供給filter。 然后就簡單多了

frequency,data = wavfile.read('Input_sound.wav')

def butter_bandpass_filter(data, lowcut, highcut, frequency, order):
    nyq = 0.5 * frequency
    low = lowcut / nyq
    high = highcut / nyq

    b, a = butter(order, [low, high], btype='bandpass')
    y = lfilter(b, a, data)
    return y 

filtered_sound=butter_bandpass_filter(data,2100,3400,44100,4)
wavfile.write('Filtered_ouput.wav',frequency,filtered_sound)