How to find the decay rate of a decaying signal ?

I have a sinusoidal sognal which decays exponentially in time. I would like to find the decay rate of the signal.

Answer 1

[Star Strider]

If it’s a simple exponential, this works:

t = linspace(0, 1, 250);
y = exp(-2*t) .* sin(50*pi*t);

env = abs(hilbert(y));                                  % Calculate Envelope
b = polyfit(t, log(env), 1);                            % Linear Regresson On Log-Transformed Data

figure(1)
plot(t, y)
hold on
plot(t, env, '-r')
hold off
grid
text(0.5, 0.75, sprintf('Decay Rate = %.3f', b(1)))