How to get the sum of the Mean absolute amplitudes of a signal ?

I truly appreciate if someone answer me. I need to measure RMS of a seismic signal and I done it with the simple rms code, but my professor asked me to measure RMS of mean absolute amplitude sum(abs(a))/N). Thank you!

signal = ...;

y = rms(signal);

Answer 1

[Théophane Dimier]

Try sqrt(mean(a.^2)), it should work in a simpler way.

Answer 2

[Théophane Dimier]

Hi!

Have you tried:

y=mean(abs(A));

?

[Maria Amr]

Théophane Dimier Thank you!

Then, how to meaure rms? rms=signal/N?

[Théophane Dimier]

sum(abs(a)/N) will give the integral of the absolute value, like mean(abs(a)).

sum(sqrt(a.^2/N)) will give the root mean square value (RMS).

But mean absolute amplitude is to me a scalar, so taking its RMS value does not make sense to me. Could it be that you have a signal in multiple direction and that you have to get the mean of the rms of the signals?

Could you describe mathematically the calculation you want to perform, please?

[Maria Amr]

Thank you again Théophane Dimier,

Actually, I have aseismic signal and I have measure the amplitude spectra in different sampling rate (fine and coarse sampling rate). Was asked me to masure RMS that I anly used a simple code:

signal = ...;

y = rms(signal);

but again was asked me to: don't use N in the square root. Try mean absolute amplitude sum(abs(a))/N. I am confused!

[Théophane Dimier]

maybe something like sqrt(mean(a.^2)) ?

But are you doing the calculation in time domain or in frequency domain?

[Maria Amr]

Théophane Dimier

Exactly. Thank you!

it seems, this code "sqrt(mean(a.^2))" gives a reasonable answer.

[Théophane Dimier]

I have copied that solution to a formal answer so you can close the question