Speech signal processing-drawing sine wave and white noise signal with MATLAB

Experiment 1 Use MATLAB to draw sine wave and white noise signals

1. Experimental requirements

(1) Use MATLAB to generate sine wave signals and white noise signals, and display their respective time-domain waveforms; (
2) Perform FFT transformation to display their respective frequency spectrums;
(3) Make the root mean square spectrum and power spectrum of the two signals , and logarithmic root-mean-square spectrum;
(4) use IFFT inverse Fourier transform to restore the signal and display the time-domain waveform.

2. Experiment source program

1. Generate a sine wave signal

%用MATLAB产生正弦波信号
fs =500;      %设定采样频率
N =180;      %计算向量的N点傅里叶变换
n =0:N-1;    %可以看成采样
t = n/fs; 
f0 = 18;      %设定正弦信号频率
 
%生成正弦信号
x = sin(2*pi*f0*t);
figure(1);
subplot(221);
plot(t,x);     %作正弦信号的时域波形
xlabel('时间/ s');
ylabel('幅值');
title('时域波形','color','red');
grid;

%进行FFT 变换并做频谱图
y = fft(x,N);   %进行FFT 变换
mag = abs(y); %求幅值
%进行对应的频率转换,即频率点（x轴的值或说是点的x坐标）
f = (0:length(y) -1)'*fs/ length(y);        
subplot(222);
plot(f,mag);   %作频谱图
axis([0,100,0,80]);
xlabel('频率/ Hz');
ylabel('幅值');
title('幅频谱图','color','red');
grid;

%求均方根谱
sq = abs(y);          
subplot(223);
plot(f,sq);
xlabel('频率/ Hz');
ylabel('均方根谱');
title('均方根谱','color','red');
grid;
 
%用IFFT 恢复原始信号
xifft = ifft(y);
magx = real(xifft);
ti = [0:length(xifft)-1] / fs;
subplot(224);
plot(ti,magx);
xlabel('时间/ s');
ylabel('幅值');
title('IFFT 后的信号波形','color','red');
grid;
sgtitle('产生正弦波信号','color','black')

2. Generate white noise signal

%****************2.白噪声****************%
fs=35;				 %设定采样频率
t = -5:0.1:5;
x = rand(1,100);
figure(2);
subplot(221);
plot(t(1:100),x);    %作白噪声的时域波形
xlabel('时间(s)');
ylabel('幅值');
title('时域波形','color','red');
grid;
 
%进行FFT 变换并做频谱图
y = fft(x);           %进行FFT 变换
mag = abs(y);         %求幅值
%进行对应的频率转换
f = (0:length(y) -1)'*fs/ length(y);            
subplot(222);
plot(f,mag);         %作频谱图
xlabel('频率/ Hz');
ylabel('幅值');
title('幅频谱图','color','red');
grid;
 
%求均方根谱
sq = abs(y);
subplot(223);
plot(f,sq);
xlabel('频率/ Hz');
ylabel('均方根谱');
title('均方根谱','color','red');
grid;
 
%用IFFT 恢复原始信号
xifft = ifft(y);
magx = real(xifft);
ti = [0:length(xifft)-1] / fs;
subplot(224);
plot(ti,magx);
xlabel('时间/ s');
ylabel('幅值');
title('IFFT 后的信号波形','color','red');
grid;
sgtitle('产生白噪声信号')

3. Running results

1. Generate a sine wave signal

2. Generate white noise