positive zero crossing of a speech signal

hello. I want to find locations of positive zero crossing of a speech signal . for example how in this picture how can I locate the places that signal is zero and before that was negative?

Answer 1

[Star Strider]

Try this:

t = linspace(0, 1, 150);                            % Create Data
s = sin(2*pi*t*5);                                  % Create Data

zci = @(y) find(diff(sign(y)));                     % Find Approximate Zero Crossing Indices
szx = zci(s);                                       % Approximate Zero Crossing Indices

for k = 1:numel(szx)
    idx = szx(k) + [0 1];
    tzx(k) = interp1(s(idx), t(idx),0);             % Interpolate To More Precise Zero-Crossings
    dsdt(k) = diff(s(idx))./diff(t(idx));           % Derivative
end

figure
plot(t, s)
hold on
pzx = tzx(dsdt>0);                                  % Derivative Greater Than 0
plot(pzx, zeros(size(pzx)),'^r')
hold off
grid
legend('Signal', 'Positive Zero Crossings')

Use your own time vector for ‘t’ and signal vector for ‘s’.

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