# How to find the Zero Crossing Rate of a signal?

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Kwaku Owusu on 19 Jan 2021
Answered: Frantz Bouchereau on 13 Oct 2021
Please, I want to determine the Zero Crossing Rate of an Acoustic Signal. I would be glad if someone could provide me with a code in Matlab to carry out such exercise,

Star Strider on 29 Jan 2021
Try this:
t = linspace(0, 5, 500).^3; % Time Vector
s = sin(2*pi*t*0.2); % 10 Hz Sine Curve
zx = find(diff(sign(s))); % Zero-Crossing Indices To ‘t’
for k = 1:numel(zx)
idx_rng = max(zx(k)-1, 1):min(zx(k)+1,numel(t));
tzro(k) = interp1(s(idx_rng), t(idx_rng), 0); % Exact Zero Crossings
end
zx_rate = gradient(tzro); % Calculate Rate
figure
yyaxis left
plot(t, s, '-b')
hold on
plot(tzro, zeros(size(tzro)), 'xr')
hold off
yyaxis right
plot(tzro, zx_rate, 'LineWidth',2)
grid
legend('Signal','Zero-Crossings','Zero-Crossing Rate')
axis('tight')
Once you have the zero-crossings, you can do whatever processing on them that you want.
.

Frantz Bouchereau on 13 Oct 2021
Signal Processing Toolbox in MATLAB R2021b ships a new zerocrossrate function that you can use to find zero crossing rates of a signal.

Mathieu NOE on 19 Jan 2021
hello
i am not sure what a "rate" can be about zero crossing, but at least maybe this code will give you access to zero or whatever threshold value crossing detection
positive slope and negative slope are detected separatly
hope it helps !
Kwaku Owusu on 29 Jan 2021
Please, I cannot see the code provided. Thank you.

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