By using a multichannel soundcard together with more than two loudspeakers or a 3D-headphone with more than one speaker per ear.
The same way as you do with ordinary audio tracks. In the box at the beginning of an Audacity audio track, move the “panorama” slider (the lower slider below the “Mute” and “Solo” buttons) from out of the middle to the left or right, then go to the Audacity “Tracks” menu and apply “Mix and Render”.
Depends on the earphone. Cheap earphones cannot reproduce high frequency signals very well. Earphones with reasonable quality should not have any problems to reproduce signals between 17500 and 22050 Hertz. Piezo speakers if used with high volume levels can cause ear damage, even if you don’t “hear” the signal. Please be careful.
I’m not sure what you mean here. The plugin produces a single-side-band modulated signal with a suppressed carrier, so if the output frequency “matches” the suppressed carrier (the carrier itself should not appear in the output signal) then it’s a bug in the plugin. But I think that this is not what you meant.
You can test the output signal yourself by first applying the “Subliminal” effect, then select a piece ot the subliminal audio track, and then go to the Audacity “Analyze” menu and apply the “Frequency Analysis”. In the analysis window there should only appear frequencies above 17500 Hertz.
See also the text box directly below how to convert the “Subliminal” signal back to normal speech again.
The “RFT” in edgar-rft is the german abbreviation for audio/video recoding equipment electrician. I only translated the electrical description in Lowry’s patent paper into Nyquist code. I cannot promise that the “Subliminal” plugin (or any other subliminal message machine) produces any useful result.
I generally try to be unbiased in answering this question, but I think that it is mainly matters if you believe in subliminal messages or not.
1. If I get up early in the morning and think “everything is bad” then probably the whole day long everything will appear as “bad” to me, mainly because I make myself think that everything is bad, even if the day is good. The same effect can also work the other way around. Strictly spoken, I do not necessarily need subliminal messages to make me feel good, it’s mainly my own thinking that infuences my perception, often much more than I am really aware of this. Maybe subliminal messages can help me to think “good”, so I have nothing against subliminal messages, but I cannot promise that it really works.
2. There had been a predecessor “ultrasonic” plugin in the german Audacity forum, that had originally been written for a dog training school. They had a 192kHz soundcard playing ultrasonic “dog commands” over a piezo speaker system. The dogs, who can hear ultrasonic sounds, then learned to do things according to the signals, where the humans hear nothing. Some time later I was notified via some posts in the german Audacity forum that people reported success by using the “ultrasonic” plugin to produce subliminal messages. To me it was instantly clear that the “ultrasonic” plugin couldn’t work on a 44100Hz soundcard because the signals produced by the plugin were above 30000Hz, which cannot be reproduced with 44100Hz sample frequency. In some subsequent discussions I prooved several times that the “ultrasonic” plugin with 44100Hz sample frequency only produced signals containing not more “message” than contained in dust-buster noise, but people were still continuing claiming “astonishing success” and similar nonsense, where the “subliminal” messages produced by the old “ultrasonic” plugin on standard 44100Hz soundcards contained nothing but pure audio garbage and no “message” at all. This is another proof that it’s our own wishing or thinking that mainly influences our perception. But at the same time this is another reason why it is very hard to decide if subliminal messages really work or are pure “placebo” effect mainly based on simple self-suggestion.
The current “Subliminal” plugin:
With the help of Karl J. Wargan and Steve’s link to Lowry’s US-patent it was possible to “translate” the description of the original Lowry machine, that used two slightly de-tuned radio transmitters to produce the subliminal audio signal, into Nyquist code that saves the up/down frequency transformation. Lowry didn’t have digital filters at that time, so it was “easier” first to produce a SSB-modulated shortwave signal and then transform it down to the audio range, but the output signal is exactly the same. I have to admit that I do not have an original Lowry machine to compare the signals, so it’s only “mathematically” identical, but the probability is very high that both signals are also physically identical. Please complain if you find problems.
I am still interested to test the “Subliminal” plugin in some medical context.