Butterworth filter python

Question

我想使用Butterworth带通过滤wav文件。我试图将wav文件转换为fft，然后应用带通滤波器，然后再应用ifft。从图形上看，它似乎经过了一些滤波，但是当我同时减少输入和输出wav时，音频没有差异，就像滤波器无法正常工作一样。有错吗

# 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

[以lfilter documentation为例，看来您不需要执行FFT，而是直接将data提供给滤波器。这样就更简单了

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)