MATLAB: Can I not use findpeaks with this audio signal

errorfrequencyMATLABpeaksSignal Processing Toolbox

Honestly not used the software much at all I understand this may be a very simple problem. My aim is to spectrally analyse an audio signal and extract its modes (frequency peaks) to spectrally model in max msp. Also if anyone knows a better way to find out the frequencies and amplitudes of peaks of an audio signal please let me know. Below is the code that will not work, I have also attached the audio sample I would like to analyze:

clear;
clc;
close all;
[audio_file, Fs] = audioread("honours_gun.wav");
findpeaks(audio_file);

Below is the error it returns:

Error using findpeaks

Expected Y to be a vector.

Error in findpeaks>parse_inputs (line 199)

validateattributes(Yin,{'double','single'},{'nonempty','real','vector'},…

Error in findpeaks (line 136)

= parse_inputs(isInMATLAB,Yin,varargin{:});

Error in Test (line 5)

findpeaks(audio_file);

Best Answer

The findpeaks function takes a vector input for the first argument. Note that ‘audio_file’ is a (8447 x 2) (stereophonic) matrix.

Use:

findpeaks(audio_file(:,1));

findpeaks(audio_file(:,2));

instead.

I doubt that you will get any useful information from using findpeaks as you are, with no additional arguments.

Related Solutions

MATLAB: How to use findpeaks in the frequency domain

I would do something like this:

[audio_file, Fs] = audioread("honours_gun.wav");
L = size(audio_file,1);
Ts = 1/Fs;                                                      % Sampling Interval
Fn = Fs/2;                                                      % Nyquist Frequency
FT_af = fft(audio_file)/L;                                      % Fourier Transform
Fv = linspace(0, 1, fix(L/2)+1)*Fn;                             % Frequency Vector
Iv = 1:numel(Fv);                                               % Index Vector
[PksL,LocsL] = findpeaks(abs(FT_af(Iv,1))*2, 'MinPeakHeight',4E-3);
[PksR,LocsR] = findpeaks(abs(FT_af(Iv,2))*2, 'MinPeakHeight',4E-3);
figure
subplot(2,1,1)
plot(Fv, abs(FT_af(Iv,1))*2)
hold on
plot(Fv(LocsL), PksL, '^r', 'MarkerFaceColor','r')
hold off
ylabel('Amplitude')
title('Left Channel')
subplot(2,1,2)
plot(Fv, abs(FT_af(Iv,2))*2)
hold on
plot(Fv(LocsR), PksR, '^r', 'MarkerFaceColor','r')
hold off
xlabel('Frequency (Hz)')
ylabel('Amplitude')
title('Left Channel')

The frequency peaks are in ‘Fv(LocsL)’ and ‘Fv(LocsR)’ respectively. The peak values for each correspond to those.

Experiment (especially with the findpeaks name-value pairs) to get the result you want.

MATLAB: What do I need to add to the code when using loglog to plot

Hi Taylor Grey,

the mistake is in the line when you call the loglog function.

loglog(Fv, 20*log10(abs(FT_af(Iv,2))*2)), xlabel('Frequency, Hz', ylabel('Amplitude, dB'));

you are using the function ylabel as an argument for xlabel, while instead you should separate those commands.

loglog(Fv, 20*log10(abs(FT_af(Iv,2))*2)); xlabel('Frequency, Hz'); ylabel('Amplitude, dB');

Given the fact that you also call xlabel and ylabel later in the script, i would suggest you to just keep the last xlabel and ylabel calls in the following way:


[audio_file, Fs] = audioread("Handgun.wav");
L = size(audio_file,1);
Ts = 1/Fs;                                                      % Sampling Interval
Fn = Fs/2;                                                      % Nyquist Frequency
FT_af = fft(audio_file)/L;                                      % Fourier Transform
Fv = linspace(0, 1, fix(L/2)+1)*Fn;                             % Frequency Vector
Iv = 1:numel(Fv);                                               % Index Vector
[PksL,LocsL] = findpeaks(20*log10(abs(FT_af(Iv,2))*2), 'MinPeakHeight',-90, 'MinPeakDistance',50);
[PksR,LocsR] = findpeaks(20*log10(abs(FT_af(Iv,2))*2), 'MinPeakHeight',-90, 'MinPeakDistance',50);
figure(1);
loglog(Fv, 20*log10(abs(FT_af(Iv,2))*2));
hold on
loglog(Fv(LocsR), PksR, '^r', 'MarkerFaceColor','r')
hold off
xlabel('Frequency (Hz)')
ylabel('Amplitude (dB)')
title('Handgun')

Best Answer

Related Solutions

MATLAB: How to use findpeaks in the frequency domain

MATLAB: What do I need to add to the code when using loglog to plot

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