# What's This Sound Musically? (Included Matlab, Requires Musical Knowledge)

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#### Batuhan88

##### Newbie level 2
Hello I found a Matlab code here and modified it a bit.
It simply takes three signals with different frequencies (nots C G and E) and inputs these three signals into one signal at a 4th frequency.

Code:
  %% configure signal settings
duration = 3;                % duration in seconds
amplitude = 0.8;               % amplitude
f1 = 523;                     % frequency in Hertz
f2 = 659;
f3 = 783;
phi = 2*pi*0.5;                % phase offset, e.g.: 2*pi*0.25 = 1/4 cycle
%% configure output settings
fs = 1760;                    % sampling rate
T = 1/fs;                      % sampling period
t = 0:T:duration;              % time vector
%% create the signal
omega1 = 2*pi*f1;              % angular frequency in radians
omega2 = 2*pi*f2;
omega3 = 2*pi*f3;
partial1 = cos(omega1*t + phi)*amplitude;      % sinusoidal partial 1
partial2 = cos(omega2*t + phi)*amplitude;      % sinusoidal partial 2
partial3 = cos(omega3*t + phi)*amplitude;      % sinusoidal partial 3
signal = (partial1 + partial2 + partial3)/3;
%signal = (partial1 );
%% plot the signal
plot(t, signal);
xlabel('Time (seconds)');
ylabel('Amplitude');
title('Complex Signal');
%% play the signal
sound(signal, fs);
%% save signal as stereo wave file
stereo_signal = [x1; x1]';
wavwrite(stereo_signal, fs, 'test.wav');

If i didn't get it wrong, this code envelopes f1 f2 f3 signals (that are C G & E notes respectively) at a frequency of 440 Hz which is the A note.

So what's that i am hearing? A note? C major chord? anything like that?

Also, fs value can't take anything lower than around 1000 Hz. Why is that?

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Yes, C major chord.

fs = 1760; % sampling rate

You may hear musical tones at this low a sample rate. However sample rates for audio are normally much greater than this. I heard the figure 8kHz for video streaming. CD quality is 44.1 kHz.

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