Vector Averaging (Spectrum)

Vector averaging, also called coherent averaging, or time or angle synchronous averaging, can reduce the noise floor in an even-angle signal.

Vector averaging computes the complex quantity and averages the real and imaginary parts of the even-angle signal separately. Use vector averaging when you already have some knowledge of the signal and want to reduce the noise floor in the signal. The NI Sound and Vibration Measurement Suite computes vector averaging for order power spectra according to the following equation:

〈 x * 〉 ⋅ ⁢ 〈 x   〉  

where X is the complex FFT of the even-angle signal X, and X* is the complex conjugate of X.

When performing vector averaging, use a triggered even-angle signal. Otherwise, you might eliminate strong order components in the averaged spectrum.