I have been using Audacity to make subliminal tracks for about 2 months now. And previously everything seemed fine. After applying subliminal there was not only, an oscillating graph for the result, but there was also volume levels showing activity. But now when I apply subliminal on both Windows and Ubuntu, it shows a graph initially but no volume activity exists when I play the subliminal track alone. Also afterwards if I import the .wav audio into audacity again to check things, it shows a complete flatline - no oscillation.
Here is the cntents of the Nyquist Command window that I have pasted there:
;nyquist plug-in
;version 1
;type process
;name "Subliminal..."
;action "Subliminal..."
;control carrier "Carrier" real "Hz" 17500 14000 20000
(setf carrier (max 14000 (min carrier 20000)))
;; We have two Nyquist frequencies, carrier/2 and *sound-srate*/2.
;; The CUTOFF is the maximum allowed frequency in the modulator.
;; It must not be greater than carrier/2, but also not greater than
;; the difference between the carrier and *sound-srate*/2, because
;; otherwise the modulated carrier aliases.
(setf cutoff (min (/ carrier 2.0) (- (/ *sound-srate* 2.0) carrier)))
(defun cut (function sound frequency)
(dotimes (ignore 10 sound)
(setf sound (funcall function sound frequency))))
(defun subliminal (sound)
(let ((result (mult 2 (cut #'lowpass8 (hp sound 80) cutoff)
(hzosc carrier))))
(cut #'highpass8 result carrier)))
(if (< *sound-srate* 44100)
(princ "The track sample frequency must be minimum 44100Hz.")
(multichan-expand #'subliminal s))
Like I said, everything used to be fine.
When I import my audio clip it’s 24000 Hz, but I always resample it to 44100 Hz. Actually if I don’t do that Nyquist Prompt won’t function and will throw an error.
If you generate a “Chirp” with the settings set at their defaults (shown below) and then apply the Nyquist “subliminal” effect, does that work as expected?
Yes, I see the wave. But if I export it and then re-import it, the wave disappears too. Debug results are completely blank. Audacity doesn’t report any errors whatsoever.
What format are you exporting as?
It’s very likely that compressed format such as MP3 will remove the very high frequency content as they are designed to remove inaudible parts of the audio so as to create a smaller file while retaining as much of the audible sound as possible.
I have tried both .wav and MP3 formats. They both produce flat lines. Even if it were because of a format issue, when I play the subliminalized track in Audacity, the volume indicator should show something - like it used to previously -, even though we don’t actually hear the chirp any longer.