9 . ▁These ▁exact ▁values ▁place ▁zeros ▁at ▁the ▁third ▁and ▁fourth ▁s idel ob es , ▁but ▁result ▁in ▁a ▁dis continu ity ▁at ▁the ▁edges ▁and ▁a ▁ 6   d B / oct ▁fall - off . ▁ ▁The ▁trunc ated ▁coefficients ▁do ▁not ▁null ▁the ▁s idel ob es ▁as ▁well , ▁but ▁have ▁an ▁improved ▁ 1 8   d B / oct ▁fall - off . ▁ ▁N utt all ▁window , ▁continuous ▁first ▁derivative ▁▁ ▁The ▁continuous ▁form ▁of ▁N utt all ▁window , ▁ ▁and ▁its ▁first ▁derivative ▁are ▁continuous ▁everywhere , ▁like ▁the ▁Hann ▁function . ▁That ▁is , ▁the ▁function ▁goes ▁to ▁ 0 ▁at ▁ ▁unlike ▁the ▁Black man – N utt all , ▁Black man – H arr is , ▁and ▁Ham ming ▁windows . ▁ ▁The ▁Black man ▁window ▁() ▁is ▁also ▁continuous ▁with ▁continuous ▁derivative ▁at ▁the ▁edge , ▁but ▁the ▁" ex act ▁Black man ▁window " ▁is ▁not . ▁ ▁Black man – N utt all ▁window ▁ ▁Black man – H arr is ▁window ▁▁ ▁A ▁general ization ▁of ▁the ▁Ham ming ▁family , ▁produced ▁by ▁adding ▁more ▁shift ed ▁s inc ▁functions , ▁meant ▁to ▁minim ize ▁side - lo be ▁levels ▁ ▁Fl at ▁top ▁window ▁▁ ▁A ▁flat ▁top ▁window ▁is ▁a ▁partially ▁negative - valu ed ▁window ▁that ▁has ▁minimal ▁scal lop ing ▁loss ▁in ▁the ▁frequency ▁domain . ▁That ▁property ▁is ▁des irable ▁for ▁the ▁measurement ▁of ▁amplit udes ▁of ▁sin