# Amplitude Modulation and Carrier Wave Addition

Hi,

I want to reconstruct what is described in this section of a paper and because I don’t want to buy a signal generator I want to use Audacity to test for feasibility. I have a mono track and used these two Nyquist Codes:
AM:

``````(mult s (hzosc 28000 *table* 90))
``````

f_c is then 28000Hz and n_1 is 1 (looks good to me, nothing gets cropped), right?
CWA:

``````(mult 0.5 (sum s (hzosc 28000 *table* 90)))
``````

f_c is then 28000Hz and n_2 is 2, right?

Somehow the resulting signal does not do what it is supposed to do.
Am I doing everything correct here? Some tutorials state you need to add 1 and multiply by 0.5 before applying AM.

Thank you! If you want 100% modulation, then the “message” needs to have a range of 0 to 1.

If this is about “Silent Subliminals”, then this topic may help: https://forum.audacityteam.org/t/silent-subliminals-solved/20100/1
Also, note that sound cards are designed for humanly audible sound, so they are often limited to a maximum analog in / out frequency of not much more than 20 kHz (even if they support sample rates of 192 kHz or more).

Ok, so the nyquist code should be:

``````(mult (mult 0.5 (sum 1 s)) (hzosc 28000 *table* 90))
``````

for a 0.5 modulation index?

With a 0 dB (full scale) “message” envelope, the modulation will be 100% By the way, in the current “version 4” syntax, that code could be written as:

``````(mult 0.5 (sum 1 *track*)(hzosc 28000))
``````