# Is negative frequency important in calculating Spectral Moments

A follow on question form this one (What is meant by "spectral moment"?)

In answers to the above referenced question spectral moment is defined as:

$$m_k=\int_{-\infty}^{\infty} f^k|X(f)|^2\ df$$

The limits on the integral include negative frequency. So is the negative frequency really important?

If I filter out all negative frequencies before calculating the moments will they be wrong?

If $|X_f|^2$ is symmetrical about zero then does this not mean that $m_k=0$ for all odd values of $k$?

• Note that your equation is wrong. You need to take the magnitude squared of the spectrum. – MBaz Jun 11 '15 at 14:46
• Ok. Edited. Thanks. How about the point of negative frequency? – Ron Jun 11 '15 at 14:49