Matlab1/3 Octave analysis different with ArtemiS

Hi All:

I am new in signal processing and I am trying to do a work in noise control and I would like get the same result with ArtemiS did.

My matlab code is:

clear;

fs = 48000.0;

x = load('x.txt');

data = load('data.txt');

result = load('result.txt');

L = 16384; % ???

nfft=8192; % ???

noverlap = 50;

window = hanning(L);

[pxx,f]=pwelch(data, window, noverlap, nfft, fs, 'centered','power');

p = poctave(pxx, fs, f, 'power', 'BandsPerOctave',3, 'FrequencyLimits',[20 20000]);

figure;

plot(x, result, 'r', x, p, 'b');

xlim([-1000 21000])

ylim([-0.1 1.6])

legend('ArtemiS','Matlab')

ArtemiS config is :

This is the result:

Does anyone know why the output are different?

The function poctave has a paramter : FilterOrder — Order of bandpass filters(6 default | positive even integer), may be cause the data difference, anyone who know how to disable it?

[Walter Roberson]

What is the difference between this and https://www.mathworks.com/matlabcentral/answers/2038221-output-of-1-3-octave-analysis-different-with-artemis?s_tid=srchtitle ?

[yingbo]

No difference actually. New one add the data file and updated code.

Answer 1

[yingbo]

clear;

fs = 48000.0;

x = load('x1.txt');

y = load('data04.txt');

result_ArtemiS = load('result04.txt');

win_length = 8192;

NFFT = 8192;

overlap = 0.50;

window = hanning(win_length);

[S, F] = spectrogram(y, window, overlap * NFFT, NFFT, fs);

frequencies = [20,25,31.5,40,50,63,80,100,125,160,200,250,315,...

400,500,630,800,1000,1250,1600,2000,2500,3150,...

4000,5000,6300,8000,10000,12500,16000,20000];

result_Matlab = zeros(length(frequencies), 1);

for i = 1:length(frequencies)

f_low = frequencies(i) / 2^(1/6);

f_high = frequencies(i) * 2^(1/6);

[~,f_low_idx] = min(abs(F - f_low));

[~,f_high_idx] = min(abs(F - f_high));

temp = S(f_low_idx:f_high_idx, :);

temp = temp(:);

temp = temp';

temp = abs(temp);

result_Matlab(i) = sqrt(sum(temp.^2));

end

result_Matlab(4) = result_Matlab(4) / 2;

result_Matlab = result_Matlab / 26933;

figure;

plot(x, result_ArtemiS, 'r-o', x, result_Matlab, 'b-o');

Answer 2

[yingbo]

x changed from Frequency Bands to 1...31

Answer 3

[yingbo]

The function poctave has a paramter : FilterOrder — Order of bandpass filters(6 default | positive even integer), may be cause the data difference, anyone who know how to disable it?