In the Nyquist plugins to perform A-Weighted measurements I've seen this code.

; A-weighted version of sound - by Edgar (thanks!)

(setq sa (lp (lp (hp (hp (hp (hp s-in 20.6) 20.6) 107.7) 737.9) 12200) 12200))

1) Is this the order in which the data will pass, which makes sense but I just want to be sure.

2) 20.6 and 1200 are used twice in a row. Should I take this to mean this is the equivalent of a 2nd order filter and all other reference are 1st order?

3) What would be the simplest, not the most elegant way to calculate LEQ?

hp 20.6

hp 20.6

hp 107.7

hp 737.9

lp 1200

lp 1200

Thank you,

W.