Time-Frequency analysis using WAV file

Hello Team,

As a part of project I need to plot frequency- time plot of WAV file. Anyway I have figured out plotting the graph using some external code (Examples) and now I have a issue how do I get the plot in milliseconds as time on x-axis since my wav file is of 60 seconds and I have to do deep analysis of graph by give limits to time and clear graph. Here I attach the code that i'm using and the graphs..

clear, clc, close all

[x, fs] = audioread('test.wav');   
x = x(:, 1);                        


xlen = length(x);                   
t = (0:length(x)-1)/fs;
plot(t*1E+3, x);

wlen = 1024;                        
nfft = 4*wlen;                      
hop = wlen/4;                      

TimeRes = wlen/fs;                  
FreqRes = 2*fs/wlen;               


TimeResGrid = hop/fs;               
FreqResGrid = fs/nfft;              


w1 = hanning(wlen, 'periodic');
[~, fS, tS, PSD] = spectrogram(x, w1, wlen-hop, nfft, fs);
Samp = 20*log10(sqrt(PSD.*enbw(w1, fs))*sqrt(2));


w2 = hanning(xlen, 'periodic');
[PS, fX] = periodogram(x, w2, nfft, fs, 'power');
Xamp = 20*log10(sqrt(PS)*sqrt(2));


figure(1)
subplot(3, 3, [2 3])
plot(t, x)
grid on
xlim([0 max(t)])
ylim([-1.1*max(abs(x)) 1.1*max(abs(x))])
set(gca, 'FontName', 'Times New Roman', 'FontSize', 12)
xlabel('Time, s')
ylabel('Amplitude')
title('The signal in the time domain')


subplot(3, 3, [4 7])
plot(fX, Xamp)
grid on
xlim([0 max(fX)])
ylim([min(Xamp)-10 max(Xamp)+10])
view(-90, 90)
set(gca, 'FontName', 'Times New Roman', 'FontSize', 12)
xlabel('Frequency, Hz')
ylabel('Magnitude, dB')
title('Amplitude spectrum of the signal')

subplot(3, 3, [5 6 8 9])
surf(tS, fS, Samp)
shading interp
axis tight
box on
set(gca, 'FontName', 'Times New Roman', 'FontSize', 12)
xlabel('Time, s')
ylabel('Frequency, Hz')
title('Amplitude spectrogram of the signal')
view(0, 90)

hcol = colorbar('East');
set(hcol, 'FontName', 'Times New Roman', 'FontSize', 12)
ylabel(hcol, 'Magnitude, dB')

disp(['Frequency resolution of the analysis: ' num2str(FreqRes) ' Hz'])
disp(['Time resolution of the analysis: ' num2str(TimeRes) ' s'])
disp(['Resolution of the frequency grid: ' num2str(FreqResGrid) ' Hz'])
disp(['Resolution of the time grid: ' num2str(TimeResGrid) ' s'])
view(-45,65)
colormap bone

[John Marriott]

Hi Venkata,

Im not sure I understand your problem - do you wish to plot all 60 seconds of the time series but with the x axies displaying milliseconds in which case you would just need to use the set the xtick properties e.g set( gca, 'Xtick', [0 20 40 60]/1000) and then set the xlabel to 'Time ms' or do you wish to plot just a snippet of the data with each point on the x axis indicating 1 milliecond?

[Venkata Naga Rohith Tinnanuru]

Hi John,

Thanks for your reply and I want each point on x-axis indicating milliseconds anyway by zooming graph we will get into milliseconds and i'm thinking is there any syntax so that I get into milliseconds without zooming the graph.

[John Marriott]

Hi Venkata

for you figure subplot(3,3,[2 3])

we can plot easily the time as milliseconds e.g plot(t*1E+3, x);

this has been shown on a previous post https://uk.mathworks.com/matlabcentral/answers/369037-plot-time-of-audio-file-in-milliseconds

but in order to include a xtick or point of x axis for every 1 millisecond we would need to set the xtick propteris e.g using set(gca, 'XTick',[0:60000])

note however that this would be almost impossible to see on a normal sized screen - with this resolution on the x axis, plotting my own audio data i was only able to accurately read 100 milliseconds of data at any one time.

[Venkata Naga Rohith Tinnanuru]

Hello John, thanks for your advice and i'll look into it and if I have any questions i'll post in community.

[Nega Ejjigu]

Can somebody help on to edit the above code so it would accept 2 .wav files then to plot in one graph?

Only I need Amplitude spectrum figure (freq Vs magnitude)

Appreciated in advance for help

Answer 1

[Nega Ejjigu]

wondering if some one able to rewrite the above code to accept 2 wav files input then two plot just frequency domain in one plot

Thanks for help in advance

[Walter Roberson]

This is not an Answer to the Question that was asked, and you need to create completely different plots than are used here.

I outlined what you need to do in your Question https://www.mathworks.com/matlabcentral/answers/1446844-i-have-two-wav-input-files-recorded-for-30-seconds-with-fs-44-100-need-to-plot-frequency-domain-in?s_tid=srchtitle