Harmonic masking by two data windows
John C. Burgess · The Journal of the Acoustical Society of America · 1979
Two practices sometimes used in digital spectrum analysis are (a) using a 1/10 cosine taper at each end of a data record and (b) augmenting a short data record with zeros. Each practice is equivalent to using a data window. The spectra of both a 1/10 cosine taper data window and of a rectangular data window with 10% contiguous zeros have significant side lobe structures at amplitude ratios below about −20 dB. The use of either procedure can lead to effective masking of low-level harmonic components in the spectral representation of a data record. When there are sufficient data to provide a required record length, leakage is most effectively reduced by using a data window designed for that purpose [see, e.g., J. C. Burgess, J. Acoust. Soc. Am. Suppl 1 65, S61(A) (1979)]. If a data record must be augmented with zeros. the undesirable effects of the rectangular window can be reduced considerably by both using a low-leakage window and placing the zeros equally at each end of the data record.