Arrays have incompatible sizes for this operation.

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Hi everyone, I'm just getting started in audio signal processing and I have some trouble trying an example of the function splMeter.
Acording to the documentation I should be able to monitor sound pressure level for octave and fractional-octave bands but I get the mesagge
''Arrays have incompatible sizes for this operation.'' . Any idea how to fix this?
DOCUMENTATION SITE: https://la.mathworks.com/help/audio/ref/splmeter-system-object.html
%% Octave SPL Metering
% The |splMeter| enables you to monitor sound pressure level for octave and
% fractional-octave bands. In this example, you monitor the
% equivalent-continuous sound pressure level of 1/3-octave bands.
%%
% Create a |dsp.AudioFileReader| object to read in an audio file frame by
% frame. Create an |audioDeviceWriter| object so you can listen to the
% audio signal. Create an |splMeter| to measure
% the octave sound pressure level of the audio file. Use the default
% calibration factor of 1. Create a |dsp.ArrayPlot| object to visualize the
% equivalent-continuous SPL for each octave band.
source = dsp.AudioFileReader('/Users/noam/Desktop/whole.mp3');
fs = source.SampleRate;
player = audioDeviceWriter('SampleRate',fs);
SPL = splMeter( ...
'Bandwidth','1/3 octave', ...
'SampleRate',fs);
centerFrequencies = getCenterFrequencies(SPL);
scope = dsp.ArrayPlot(...
'XDataMode','Custom', ...
'CustomXData',centerFrequencies, ...
'XLabel','Octave Band Center Frequencies (Hz)', ...
'YLabel','Equivalent-Continuous Sound Level (dB)', ...
'YLimits',[20 90], ...
'ShowGrid',true, ...
'Name','Sound Pressure Level Meter');
%%
% In an audio stream loop:
%
% # Read in the audio signal frame.
% # Play the audio signal to your output device.
% # Call the SPL meter to return the equivalent-continuous sound pressure
% level in dB.
% # Display the sound levels using the scope. Update the scope only when
% the equivalent-continuous sound pressure level has changed.
%
% As a best practice, release your objects once complete.
%
LeqPrevious = zeros(size(centerFrequencies));
while ~isDone(source)
x = source();
player(x);
[~,Leq] = SPL(x);
for i = 1:size(Leq,1)
if LeqPrevious ~= Leq(i,:)
scope(Leq(i,:)')
LeqPrevious = Leq(i,:);
end
end
end
release(source)
release(player)
release(SPL)
release(scope)

Answers (1)

VBBV
VBBV on 1 Aug 2022
Edited: VBBV on 1 Aug 2022
LeqPrevious = zeros(1,30,2); % array preallocation is not the sme size of Leq
LeqPrevious = Leq(i,:,:); % inside the loop Leq is of size 1024x30x2
Array assignment inside the if - loop is not of same size. Change the size of preallocatied array to that of Leqprevious

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