Repeated notch filters at 1KHz intervals gets rid of most of it …
Copy and paste the code below into something called “Nyquist Prompt”, which is in the Audacity “Effects” menu.
(setq mysound s)
(setq q 10) ; set the base Q for the filter
(setq iter 15) ; set the number of iterations
(setq freq 1000) ; set base frequency
; start the DO loop
(dotimes (i iter mysound)
(setf mysound (notch2 mysound (* freq (1+ i)) (* q (1+ i))))
) ;end of loop
[ code originally from here … https://forum.audacityteam.org/t/multiple-notches-with-nyquist-prompt/7583/3 ]