WarpMyMind

On the audacity forum there are two different ways listed to produce a silent subliminal.

The first way, or the manual way (https://forum.audacityteam.org/viewtopi ... 13&t=53615)
This method produces a track with audible "tweets" and sounds, though no words are discernible.


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The second way, involves use of a plug-in (https://forum.audacityteam.org/viewtopi ... 42&t=58548).
This method produces a track that is truly silent.

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My question is, which method of encoding produces the best results?
I have experimented with both and have seen mixed results/limited success using both methods.

I Want to see if anyone else has experimented with these, or other encoding methods - And what success they have seen.

I have always had the best luck with a second audio track (or seperate left right tracks) about -32db below the main audio. Conscious audible to some listeners but very effective.

After experimentation, I have found that using the first method(that produces the tweets)- to be more effective.
I have simply been turning the volume down to a point where the "tweets" are less obvious.

Both listed "methods" are essentially the same, but fed slightly different parameters. You can achieve the same results with each.
Note that there are other "true" methods, such as level control, masking, etc... Also note that these are not mutually exclusive - you can use multiple methods of encoding on the same source, and overlay them into the same result file.

I have been searching Audacity for a function which does the following. I know there is hardware to do this but I was hoping for software.

Assume a stereo track with music. Also a track with speech to be used as a subliminal.

The resulting track would be such that the audio track would always be some lower volume (perhaps -20db) from the values in the music track.

This means that during quiet parts of the music, the speech would still be the same -20db below the quiet music level.

@Maleko7: You're looking for an envelope follower. From audacity forum searching (mostly Steve's posts), I pieced together a rudimentary nyquist plugin for this as follows:

Code: Select all

;nyquist plug-in
;version 1
;type process
;name "Envelope Follower"
;action "Envelope Follower..."
;control blksz "Block Size (default 1000)" int "samples" 1000 100 2000
;control stpsz "Step Size" int "must be less than or equal to block size" 1000 100 2000
;control flr "Floor (default 0.001)" real "seconds" 0.001 0.0 1.0
;control rstm "Rise time (default 0.1)" real "seconds" 0.1 0.0 1.0
;control fltm "Fall time (default 0.2)" real "seconds" 0.2 0.0 1.0
;control lkahd "Look Ahead (default 2)" int "samples" 2 1 2000

(setf R-CHAN (aref s 1))

(setf LOW-R-SOUND
(let*
((blocksize blksz)
(stepsize stpsz))
(snd-avg R-CHAN blocksize stepsize OP-PEAK)))

(setf ENVELOPE
(let
((floor 0.001)
(risetime rstm)
(falltime fltm)
(lookahead lkahd))
(snd-follow LOW-R-SOUND floor risetime falltime lookahead)))

(mult (aref s 0) ENVELOPE)


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For finer following of the envelope, I changed the code to this:

Code: Select all

;nyquist plug-in
;version 1
;type process
;name "Envelope Follower 100"
;action "Envelope Follower 100..."
;control blksz "Block Size (default 100)" int "samples" 100 100 500
;control stpsz "Step Size" int "must be less than or equal to block size" 100 100 500
;control flr "Floor (default 0.001)" real "seconds" 0.001 0.0 1.0
;control rstm "Rise time (default 0.1)" real "seconds" 0.1 0.0 1.0
;control fltm "Fall time (default 0.2)" real "seconds" 0.2 0.0 1.0
;control lkahd "Look Ahead (default 2)" int "samples" 2 1 500

(setf R-CHAN (aref s 1))

(setf LOW-R-SOUND
(let*
((blocksize blksz)
(stepsize stpsz))
(snd-avg R-CHAN blocksize stepsize OP-PEAK)))

(setf ENVELOPE
(let
((floor 0.001)
(risetime rstm)
(falltime fltm)
(lookahead lkahd))
(snd-follow LOW-R-SOUND floor risetime falltime lookahead)))

(mult (aref s 0) ENVELOPE)


These plugins are used in the same way that the vocoder plugins are used; make stereo track from voice on top (left channel) and music on bottom (right channel), run plugin, then stereo track to mono. Must be done twice, once for left channel of music, once for right channel of music. Experiment, learn and have fun.

Hope that helps.

Envelope following is usually unnecessary for subliminals, just put it at -35db and add a noise track at -32db to cover it... adds a teeny bit of background noise but makes the subliminal inaudible during the quiet parts (if you care, slightly supraliminal suggestions can be just as effective as true subliminals)

Thank you or You, JackDrago. This was useful advice!

Regards
Z