ering , ▁not ▁segment ation , ▁is ▁the ▁main ▁purpose ▁of ▁window ▁functions . ▁ ▁The ▁reasons ▁for ▁exam ining ▁segments ▁of ▁a ▁longer ▁function ▁include ▁detection ▁of ▁trans ient ▁events ▁and ▁time - aver aging ▁of ▁frequency ▁spect ra . ▁ ▁The ▁duration ▁of ▁the ▁segments ▁is ▁determined ▁in ▁each ▁application ▁by ▁requirements ▁like ▁time ▁and ▁frequency ▁resolution . ▁ ▁But ▁that ▁method ▁also ▁changes ▁the ▁frequency ▁content ▁of ▁the ▁signal ▁by ▁an ▁effect ▁called ▁spectral ▁leak age . ▁ ▁Window ▁functions ▁allow ▁us ▁to ▁dist ribute ▁the ▁leak age ▁spect r ally ▁in ▁different ▁ways , ▁according ▁to ▁the ▁needs ▁of ▁the ▁particular ▁application . ▁ ▁There ▁are ▁many ▁choices ▁detailed ▁in ▁this ▁article , ▁but ▁many ▁of ▁the ▁differences ▁are ▁so ▁subt le ▁as ▁to ▁be ▁ins ign ific ant ▁in ▁practice . ▁ ▁In ▁typical ▁applications , ▁the ▁window ▁functions ▁used ▁are ▁non - negative , ▁smooth , ▁" bell - sh aped " ▁curves . ▁Rect angle , ▁triangle , ▁and ▁other ▁functions ▁can ▁also ▁be ▁used . ▁ ▁A ▁rect angular ▁window ▁does ▁not ▁modify ▁the ▁data ▁segment ▁at ▁all . ▁ ▁It ' s ▁only ▁for ▁mod elling ▁purposes ▁that ▁we ▁say ▁it ▁multip lies ▁by ▁ 1 ▁inside ▁the ▁window ▁and ▁by ▁ 0 ▁outside . ▁ ▁A ▁more ▁general ▁definition ▁of ▁window ▁functions ▁does ▁not ▁require ▁them ▁to ▁be ▁ident ically ▁zero ▁outside ▁an ▁interval , ▁as ▁long ▁as ▁the ▁product ▁of ▁the ▁window ▁multip lied ▁by ▁its ▁argument ▁is ▁square ▁integra ble ,