Analyzing Pass-By Noise Using the FFT

Dividing a vehicle pass-by test into a series of short analysis intervals and calculating a spectra for each of these intervals can provide meaningful information to help identify individual noise sources throughout the pass-by test. Due to the continuously changing instantaneous frequency and amplitude of each of the tonal components in pass-by noise data inaccuracies can occur in the spectra calculated in this manner. The questions which are addressed in this report are the selection of the frequency resolution and block size for FFT processing of pass-by test data to provide a power spectrum with acceptable accuracy for noise source identification.