How to create realistic AM bandwith radio effect

Hi. I was looking for some realistic effect of an older MW station receiption on a recorded audio. I know the effect can be done with the equalizer filter, but first of all, that creates an effect of a recording of a radio from an outer microphone, not the actual signal that comes to the radio; and second, it sounds cheap and fake.

Is there some way to create like a more realistic effect using just Audacity? Because if you listen to the MW during evening, you get like interferring stations in distance, there is fading (ionosphere propagation isn’t constant, it’s kind of pulsing), and of course the radio static in the atmosphere kind of spoils the signal, so the sound is constantly popping. Simulate weather conditions (lightning storm really breaks the MW receiption down, rain wets the air and the conductivity of the air changes, so the signal propagation is different while rainy, cloudy or sunny), that would be nice, too.

Audacity is great tool and lots of effects can be done using the standard effects library. However, I do not know whether there is some plugin that would be able to simulate those kinds of stuff. There is narrow-band noise generator, and it can be used to simulate morse-code radio station receiption (however, it will still sound fake, because it lacks that popping effect). Could I somehow generate the popping in the audio track? Or do I have to create it manually? And how could I create that fading effect? I was unable to find a plugin that would be capable of doing that.

How the fading effect actually looks like in spectrogram:

The red vertical line is the carrier of the signal, blue horizontal line is the upper side band and yellow one is lower side band. The diagonal green lines is actually the fading effect (portions where the signal is weaker). How it sounds in the demodulated audio? It’s kind of like fire ball passing by (kind of like doppler effect). Where the signal grows weaker, the static grows stronger, that’s just how it works. So missing portions of the spectrogram will have static instead, where the signal is weaker in spectrogram, there will be stronger static.

I hope I have explained it well enough for you to understand what I am looking for.
Courtesy of Wide-band WebSDR in Netherlands for this demosntrative picture: http://websdr.ewi.utwente.nl:8901

I don’t know of any plugin or filter which can do that.

I’m prompted to ask why we’re doing this. That post reads like an encyclopedic description of every distortion in the history of broadcast radio. Theater effects are normally carried with two or three noises all run through a 5KHz low pass filter. Maybe, depending on the script, a further equalization to simulate a wooden radio (you left that one out).

Fading is never used unless it’s a plot point. I remember a TV show (in black and white) which did that.

If you pile all the effects in the sound at once, the transmission wouldn’t be intelligible and if you shifted them over the course of a show, you run the risk of losing the audience who wouldn’t be able to follow you.

Koz

Okay, I may see where you’re trying to aim. Well, I’ll try to do something…

I can think of more evil reasons to want that. You’re trying to fool someone into thinking there’s a radio broadcast where none existed.

Finding background on questions like that is not the worst idea. Sometimes the poster will go down a rabbit hole with odd assumptions when we may know far simpler solutions if we just knew what the job was.

Koz

I certainly don’t want to fool anybody. I was just looking for a way to simulate the captured broadcast signal on audio of my choice. The result could as easily be used in a video game, motion picture, or just as is to demonstrate free software power. Don’t take me bad. Audacity can be used for a wide variety of purposes. It can enhance, transform and also even create audio. I can make anyone sound robotic, with just simple transform effects.

If I take Audacity, it is capable of restoring damaged audio (yep, even portions that got lost by quality wear down). It can remove crackles, popping, static noise. It’s also possible to restore lost frequency range, in case of damaged tape recording. The key is to use other references as base and try to figure out what the lost data look like.

Moving to off-topic (but still free and open-source software), Blender is capable of astonishing real-life looking renders. If you didn’t tell anybody, nobody would ever guess that thing is actually CGI. With RTX video card, the render time is almost instant.

The software is moving rapidly forward and maybe we can expect more abilities of that software to show up. For Audacity, I believe that more plugins could be produced one day, more complex ones, timing based, etc. That’s my view.

I was just looking for a way to simulate the captured broadcast signal on audio of my choice. The result could as easily be used in a video game, motion picture, or just as is to demonstrate free software power.

So you want the simulation in case a job comes up.

Koz

Audacity can do that: cyclically cross-fade signal with noise with this plugin …
https ://wiki.audacityteam.org/wiki/Nyquist_Effect_Plug-ins#Stereo_Butterfly_.28LFO.29
Use a stereo-pair with pure noise on one track, & only signal on the other.
Apply the butterfly-effect filter, then split stereo-tracks to mono & delete one of the tracks.

Alternatively could AutoDuck signal-only track with noise-only track which has varying volume.

Well, there is a software called “Reaper”, that is capable of quite realistic effect on-the-fly (see https://forum.cockos.com/showthread.php?t=86181)

I was wondering if very similar effect could be done within Audacity, too. Though not so on-the-fly but rather baked into the sound and more progressive than that Reaper project the guy made (yes, Reaper standalone doesn’t have a built-in effect for this, you have to build it on your own, or download a template), I was wondering if Audacity can produce similar results. I’ve tried it myself and I must say that the results are really great. One issue though: It doesn’t allow me to program the signal strenght over time, only one fixed value, and another issue: that program isn’t actually free and unfortunately my free 30-day trial ended a loong time ago. The on-the-fly aspect is very good, but I can manage as well without that aspect, just apply an effect and go.