谱减法降噪（python实现）

#!/usr/bin/env python
import numpy as np
import wave
import math

import ctypes as ct


class FloatBits(ct.Structure):
    _fields_ = [
        ('M', ct.c_uint, 23),
        ('E', ct.c_uint, 8),
        ('S', ct.c_uint, 1)
    ]


class Float(ct.Union):
    _anonymous_ = ('bits',)
    _fields_ = [
        ('value', ct.c_float),
        ('bits', FloatBits)
    ]


def nextpow2(x):
    if x < 0:
        x = -x
    if x == 0:
        return 0
    d = Float()
    d.value = x
    if d.M == 0:
        return d.E - 127
    return d.E - 127 + 1


# 打开WAV文档
f = wave.open("test.wav")
# 读取格式信息
# (nchannels, sampwidth, framerate, nframes, comptype, compname)
params = f.getparams()
nchannels, sampwidth, framerate, nframes = params[:4]
fs = framerate
# 读取波形数据
str_data = f.readframes(nframes)
f.close()
# 将波形数据转换为数组
x = np.fromstring(str_data, dtype=np.short)
# 计算参数
len_ = 20 * fs // 1000
PERC = 50
len1 = len_ * PERC // 100
len2 = len_ - len1
# 设置默认参数
Thres = 3
Expnt = 2.0
beta = 0.002
G = 0.9
# 初始化汉明窗
win = np.hamming(len_)
# normalization gain for overlap+add with 50% overlap
winGain = len2 / sum(win)

# Noise magnitude calculations - assuming that the first 5 frames is noise/silence
nFFT = 2 * 2 ** (nextpow2(len_))
noise_mean = np.zeros(nFFT)

j = 0
for k in range(1, 6):
    noise_mean = noise_mean + abs(np.fft.fft(win * x[j:j + len_], nFFT))
    j = j + len_
noise_mu = noise_mean / 5

# --- allocate memory and initialize various variables
k = 1
img = 1j
x_old = np.zeros(len1)
Nframes = len(x) // len2 - 1
xfinal = np.zeros(Nframes * len2)

# =========================    Start Processing   ===============================
for n in range(0, Nframes):
    # Windowing
    insign = win * x[k - 1:k + len_ - 1]
    # compute fourier transform of a frame
    spec = np.fft.fft(insign, nFFT)
    # compute the magnitude
    sig = abs(spec)

    # save the noisy phase information
    theta = np.angle(spec)
    SNRseg = 10 * np.log10(np.linalg.norm(sig, 2) ** 2 / np.linalg.norm(noise_mu, 2) ** 2)


    def berouti(SNR):
        if -5.0 <= SNR <= 20.0:
            a = 4 - SNR * 3 / 20
        else:
            if SNR < -5.0:
                a = 5
            if SNR > 20:
                a = 1
        return a


    def berouti1(SNR):
        if -5.0 <= SNR <= 20.0:
            a = 3 - SNR * 2 / 20
        else:
            if SNR < -5.0:
                a = 4
            if SNR > 20:
                a = 1
        return a


    if Expnt == 1.0:  # 幅度谱
        alpha = berouti1(SNRseg)
    else:  # 功率谱
        alpha = berouti(SNRseg)
    #############
    sub_speech = sig ** Expnt - alpha * noise_mu ** Expnt;
    # 当纯净信号小于噪声信号的功率时
    diffw = sub_speech - beta * noise_mu ** Expnt


    # beta negative components

    def find_index(x_list):
        index_list = []
        for i in range(len(x_list)):
            if x_list[i] < 0:
                index_list.append(i)
        return index_list


    z = find_index(diffw)
    if len(z) > 0:
        # 用估计出来的噪声信号表示下限值
        sub_speech[z] = beta * noise_mu[z] ** Expnt
        # --- implement a simple VAD detector --------------
        if SNRseg < Thres:  # Update noise spectrum
            noise_temp = G * noise_mu ** Expnt + (1 - G) * sig ** Expnt  # 平滑处理噪声功率谱
            noise_mu = noise_temp ** (1 / Expnt)  # 新的噪声幅度谱
        # flipud函数实现矩阵的上下翻转，是以矩阵的“水平中线”为对称轴
        # 交换上下对称元素
        sub_speech[nFFT // 2 + 1:nFFT] = np.flipud(sub_speech[1:nFFT // 2])
        x_phase = (sub_speech ** (1 / Expnt)) * (
                np.array([math.cos(x) for x in theta]) + img * (np.array([math.sin(x) for x in theta])))
        # take the IFFT

        xi = np.fft.ifft(x_phase).real
        # --- Overlap and add ---------------
        xfinal[k - 1:k + len2 - 1] = x_old + xi[0:len1]
        x_old = xi[0 + len1:len_]
        k = k + len2
# 保存文件
wf = wave.open('en_outfile.wav', 'wb')
# 设置参数
wf.setparams(params)
# 设置波形文件 .tostring()将array转换为data
wave_data = (winGain * xfinal).astype(np.short)
wf.writeframes(wave_data.tostring())
wf.close()

 

参考资料：

1.https://blog.csdn.net/itaacy/article/details/60141849

2.https://www.sohu.com/a/146988029_778200

3.https://www.audacityteam.org/