Um , actually it 's better to use sixty - four milliseconds because , um , if you use thirty milliseconds , then , uh , because of the  this short windowing and at low pitch , uh , sounds ,  the harmonics are not , wha uh , correctly separated.
Mm - hmm.
So if you take these minima , it  b  they will overestimate the noise a lot.
So you take sixty - four millisecond F F Ts and then you average them  over five hundred ? Or  ? Uh , what do you do over five hundred ?