Hi, Let me apologize in advance for my lack of knowledge on this subject and if I’ve posted to the wrong area! I came to the Audacity program from a link talking about tinnitus (and making your own sound therapy). The instructions that I have say to select the Nyquist filter under “effect”. There isn’t a Nyquist option there, but there is a Notch Filter under ‘Effects’ where I can select a Hz to notch. Later, I did see a Nyquist Prompt under ‘Tools’ (also Nyquist installers).
So my questions are:
Is there a big difference between the Notch and the Nyquist filters?
Is there a way for me to use the Nyquist filter (I couldn’t download or install it). I’m on MAC OS Mojave
The Nyquist filter seems a bit complicated, so is there an easy way to select a Hz to essentially ‘notch’? I’ve always been technically challenged.
If all of this has been answered before, can someone link me to the information?
“Nyquist” is a simple programming language that is built into Audacity (it’s also available as a stand-alone programming language for audio https://www.cs.cmu.edu/~music/nyquist/).
In Audacity, Nyquist scripts (programs), which are written in plain ascii text, may be made into plug-ins, by adding a few special comments to the top of the text file, and naming the file with “.ny” at the end (rather than “.txt”).
The “Notch Filter” is a plug-in for Audacity that is written in Nyquist. If you looked inside the “notch.ny” file, you would see:
$nyquist plug-in
$version 4
$type process
$preview linear
$name (_ "Notch Filter")
$manpage "Notch_Filter"
$debugbutton false
$action (_ "Applying Notch Filter...")
$author (_ "Steve Daulton and Bill Wharrie")
$release 2.3.0
$copyright (_ "Released under terms of the GNU General Public License version 2")
;; notch.ny by Steve Daulton and Bill Wharrie
;; Released under terms of the GNU General Public License version 2:
;; http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
;;
;; For information about writing and modifying Nyquist plug-ins:
;; https://wiki.audacityteam.org/wiki/Nyquist_Plug-ins_Reference
$control frequency (_ "Frequency (Hz)") float-text "" 60 0 nil
$control q (_ "Q (higher value reduces width)") float-text "" 1 0.1 1000
(cond
((< frequency 0.1) (_ "Frequency must be at least 0.1 Hz."))
((>= frequency (/ *sound-srate* 2.0))
(format nil (_ "Error:~%~%Frequency (~a Hz) is too high for track sample rate.~%~%~
Track sample rate is ~a Hz.~%~
Frequency must be less than ~a Hz.")
frequency
*sound-srate*
(/ *sound-srate* 2.0)))
(T (notch2 *track* frequency q)))
The lines beginning with “$” are the special comments that turn the code into a plug-in.
The lines that begin with one or more semicolon are normal “code comments” and are ignored.
The actual Nyquist code is just this bit:
(cond
((< frequency 0.1) (_ "Frequency must be at least 0.1 Hz."))
((>= frequency (/ *sound-srate* 2.0))
(format nil (_ "Error:~%~%Frequency (~a Hz) is too high for track sample rate.~%~%~
Track sample rate is ~a Hz.~%~
Frequency must be less than ~a Hz.")
frequency
*sound-srate*
(/ *sound-srate* 2.0)))
(T (notch2 *track* frequency q)))
I’m guessing that they are referring to the “Nyquist Prompt”, which was listed in the Effect menu in old versions of Audacity, but is now in the Tools menu in the current version of Audacity.