I have two xxx.wav input files recorded for 30 seconds in noise lab at different conditions with fs 44,100 need to plot normalized frequency Vs dB in one plot

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Nega Ejjigu 2021-9-4

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评论： Nega Ejjigu 2021-9-5

I have two .wav input files recorded for 30 seconds with fs 44,100 each . I want a matlab code for frequency analysis plot in one panel to compare two wav file inputs

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Walter Roberson 2021-9-4

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Read the files. Isolate a single channel on each. If they are different frequencies, resample to a common frequency. If one is shorter than the other, truncate the longer. Subtract the mean of each signal from the signal.

Now fft each signal. plot() the real() or imag() or abs() of the first result. Use "hold on" . plot() the real() or imag() or abs() of the second result. Label the plot.

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Nega Ejjigu 2021-9-5

编辑：Walter Roberson 2021-9-5

在 MATLAB Online 中打开

The record was done using sound meter app. My goal is I have one shielding cage built so to compare two records of sound waves in noisy lab. One record inside the cage and the second outside the cage for 30 seconds record for each then to see frequency domain plot in one panel. Iam not sure here if they are different frequencies. So I would be very glad if I can get a code that reads two input .wav files and executes normalized frequency againist dB plot for both inputs in one plot.

I got one matlab code from the forum randomly :

clear, clc, close all
[x,fs] =audioread('recordUnshield16bit.wav');  
x = x(:, 1); %Create Vector                       
xlen = length(x);
t = (0:length(x)-1)/fs;
wlen = 1024;                        
nfft = 4*wlen;                      
hop = wlen/4;      
TimeRes = wlen/fs;                  
FreqRes = 2*fs/wlen;               
TimeResGrid = hop/fs;               
FreqResGrid = fs/nfft;   
w1 = hann(wlen, 'periodic');
[~, fS, tS, PSD] = spectrogram(x, w1, wlen-hop, nfft, fs);
Samp = 20*log10(sqrt(PSD.*enbw(w1, fs))*sqrt(2));
w2 = hann(xlen, 'periodic');
[PS, fX] = periodogram(x, w2, nfft, fs, 'power');
Xamp = 20*log10(sqrt(PS)*sqrt(2));
grid on
subplot(3, 3, [4 7])
plot(fX, Xamp)
%grid on
xlim([0 max(fX)])
%ylim([min(Xamp)-10 max(Xamp)+10])
view(0, 90)
set(gca, 'FontName', 'Times New Roman', 'FontSize', 12)
xlabel('Frequency, Hz')
ylabel('Magnitude, dB')
colormap bone

Can anybody customize this code for my case? ( to read two wav inputs then to plot in one panel normalized frequency vs dB)

Thanks in advance for help

Walter Roberson 2021-9-5

在 MATLAB Online 中打开

[sig1, Fs] = audioread('s.wav');
[sig2, Fs2] = audioread('u.wav');
assert(Fs == Fs2);                                %sample rate must be same
assert(size(sig1,2) == 1 && size(sig2,2) == 1);   %single channel only supported
minlen = min(length(sig1), length(sig2));
sig1 = sig1(1:minlen);
sig2 = sig2(1:minlen);
sig1 = sig1 - mean(sig1);
sig2 = sig2 - mean(sig2);
ff1 = fftshift(fft(sig1));
ff2 = fftshift(fft(sig2));
db1 = mag2db(ff1);
db2 = mag2db(ff2);
x = linspace(-Fs/2, Fs/2, length(db1));
bnd = 1000*floor(Fs/2000);
plot(x, real(db1), 'displayname', 's');
hold on
plot(x, real(db2), 'displayname', 'u');
hold off
xticks(-bnd:1000:bnd);
xlabel('Hz'); ylabel('dB')
legend show