Windowing

Definition
When an arbitrary chunk of a digital waveform is selected, the first and last samples in the segment will almost always not be zero, and will thus be aperiodic. The spectral analysis of these arbitrary chunks will then falsely include the spectrum of a transient signal. Windowing solves this problem by modifying the amplitudes of the waveform segment so that the samples nearer the edges are low in amplitude and samples in the middle of the segment are at full amplitude. Two types of windows are the Hamming window and the rectangular window. The Hamming window reduces the amplitudes of the samples near the edges of the waveform chunk, whereas the rectangular window does not change the waveform samples at all.

Links
Utrecht Lexicon of Linguistics