import scipy.io.wavfile as wav
import scipy.signal as signal
import matplotlib.pyplot as plt
from PIL import Image

# Считываем файл
fs, data = wav.read('Arecibo.wav')

def butter_bandpass(lowcut, highcut, fs, order=5):
    nyq = 0.5 * fs
    low = lowcut / nyq
    high = highcut / nyq
    b, a = signal.butter(order, [low, high], btype='band')
    return b, a

def butter_bandpass_filter(data, lowcut, highcut, fs, order=5):
    b, a = butter_bandpass(lowcut, highcut, fs, order=order)
    y = signal.lfilter(b, a, data)
    return y

f1, f2 = 3000, 4000
data_f2 = butter_bandpass_filter(data, f2 - 200, f2 + 200, fs, order=3)