Post by reden on Jul 19, 2022 23:38:02 GMT
;nyquist plug-in
;version 1
;type process
;name "Subliminal..."
;action "Subliminal..."
;control carrier "Carrier" real "Hz" 17500 14000 20000
(setf *nyquist-srate* (/ *sound-srate* 2.0))
(setf carrier (max 14000 (min carrier (- *nyquist-srate* 3000))))
;; 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) (- *nyquist-srate* 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.")
(princ "Die Samplefrequenz der Tonspur muss mindestens 44100Hz sein.")
(multichan-expand #'subliminal s))
I tried changing the available carrier frequency range assuming that lower would mean it would be in the audible range.
However, even going down as far as 100 Hz does not yield audible sound.
Somehow, it seems it is making the waveform inaudible through some other means than ultrasound.
Of course I cannot know for sure because I don't understand half of this. But it could be a bug.
I think it's transporting the frequencies to the carrier range through a series of 10 lowpass and highpass filters.
