如何在python上对录音进行低通滤波？

import scipy.signal as signal
import numpy as np
import soundfile as sf

audio, sample_rate = sf.read('录音文件路径')

cutoff_freq = 4000  # 截止频率，可根据实际需求进行调整
nyquist_freq = 0.5 * sample_rate
normalized_cutoff_freq = cutoff_freq / nyquist_freq
b, a = signal.butter(4, normalized_cutoff_freq, btype='low', analog=False)

filtered_audio = signal.lfilter(b, a, audio)

sf.write('滤波后的录音文件路径', filtered_audio, sample_rate)