Audacity Forum

As a new user of Audicity really appreciate the Tips, Tutorials and Forum comments especially concerning 1.3.13 Alpha.

Recently read Reducing Subsonic Noise http://wiki.audacityteam.org/wiki/Reducing_noise and agree with writer (did not see name) "While removing hi-band noise might be considered optional, removing subsonic noise seems mandatory to the writer. In contrast to hi-band noise you can apply subsonic reduction as a step in the mastering process, on the mixed and processed material, before a final Normalize."

"To remove subsonics from your track you may filter it with:

* Audacity's built in Equalizer under the Effect menu
* Audacity's built-in High Pass Filter under the same menu - set the cutoff frequency to around 25 Hz. You can repeat this same effect a couple of times if a sharper cutoff slope is desired.
* This Nyquist plug-in subsonic filter. Right-click or control-click over this link, and save it as "subsonic.ny". Then drop it into the "Plug-Ins" folder in your Audacity installation folder and restart Audacity."

Did and got this:
;nyquist plug-in
;version 1
;type process
;name "Subsonic Filter"
;action ""
;info ""
;control frequency "Frequenz" real "" 20 10 100
;control steepness "Steilheit" int "" 1 1 4

(cond
((= steepness 1) (if (arrayp s)
(vector (highpass2 (aref s 0) frequency) (highpass2 (aref s 1) frequency))
(highpass2 s frequency)))
((= steepness 2) (if (arrayp s)
(vector (highpass4 (aref s 0) frequency) (highpass4 (aref s 1) frequency))
(highpass4 s frequency)))
((= steepness 3) (if (arrayp s)
(vector (highpass6 (aref s 0) frequency) (highpass6 (aref s 1) frequency))
(highpass6 s frequency)))
((= steepness 4) (if (arrayp s)
(vector (highpass8 (aref s 0) frequency) (highpass8 (aref s 1) frequency))
(highpass8 s frequency))))

As a beginner am confused as how to save? Do I save it in NotePad

Did a Forum Search using "Subsonic Filter" but got "No suitable matches were found."

Also appreciate any tips and suggestions using the Subsonic Filter?

Thanks

Ken

To save the plug-in to your computer and install it in Audacity:
Right-click or control-click over this link, and save it as "subsonic.ny". Then drop it into the "Plug-Ins" folder in your Audacity installation folder and restart Audacity.
(as it says on the "Reducing noise" wiki page).
If you clicked with the left mouse button the plug-in will usually open in the web browser and just display the text in the file rather than offering the option to save the file.

However, if you are using Audacity 1.3.12 you do not need to install this plug-in as there is already a "high pass filter" included in Audacity that can do the same job.
A "high pass filter" allows high frequencies (above the filter frequency) to pass through the filter virtually unaltered, but will increasingly reduce the level of frequencies below the filter frequency. For example, if the filter frequency is 20 Hz, then frequencies above 20 Hz will be virtually unaltered, sub-sonic sounds in the range of 10 to 20 Hz will be reduced a bit, sub-sonic sounds in the range 5 to 10 Hz will be reduced more, and frequencies below 5 Hz will be reduced a lot - the lower the frequency of the sound below the filter frequency, the more it will be cut.

"Sub-sonic" usually means sounds below 20 Hz, though in some cases you may want to start to reduce the level with a higher filter frequency, for example, if there is a lot of audible "rumble" in a recording, you may want to set a filter frequency of, say, 100 Hz.

The "steepness" of the filter (how rapidly below the filter frequency sounds are cut) is usually measured in "dB per octave". The higher the "dB per octave", the more rapidly the low frequencies will be cut.

In the "high-pass filter" effect I would recommend leaving the "filter quality" setting at the default value.