# First moment of a spectrum (Al Bregman )

```Subject: First moment of a spectrum
From:    Al Bregman  <BREGMAN(at)HEBB.PSYCH.MCGILL.CA>
Date:    Sun, 11 Jun 2000 23:44:36 -0400

Dear List Members,

I wish I knew more math, but I don't.  So I have to ask this question.

In relation to a measure of the central point in a spectrum, somebody wrote
about the "first moment" of the spectrum.  From context, it seems that the
first moment is the frequency at which the sum of the positive deviations of
frequencies above it,  multiplied by their amplitudes, is equal to the sum
of the negative deviations in frequency, of the frequencies below it,
multiplied by their amplitudes.  In other words, if the spectrum were
inscribed on a piece of tin, and then cut out, the first moment would be the
frequency at which it balanced.

Is this a correct interpretation?

Thanks,

Al
---------------------------------------------------------
Albert S. Bregman, Emeritus Professor
Dept of Psychology, McGill University
1205 Docteur Penfield Avenue