To achieve a radio communication effect in Audacity is fairly easy. First record your line from your script, normally you’d then clear up the sound with the noise removal effect and perform low and high end passes and a little light compression. But why bother, you want the recording to sound a bit rough right? Once you have recorded your line, highlight it by pressing the Ctrl key and the A key together. Then go to the menu option > Effect. From that drop down menu select > Equalization. You will then see the following screen:
Make sure acoustic is selected in the Predefined box on this screen. The blue line in the middle of the graphic equalizer is movable. Click and drag it with the mouse so that it is touching the bottom line of the area, like this:
Where you clicked on the line as you dragged and it down to the bottom edge of the box, you will see a little white marker. Everytime you click on this thick blue line you will make a new marker. You can click on these markers and move/bend the thick blue line at those points where you made the markers. So move the first marker you made so it is on the 1000 hz mark on the bottom scale line as per the picture above. Now make more markers by clicking on the line with the mouse and bend that line so it looks like the one in the picture below:
Once you have the right curve click on OK and you return to the main Audacity screen. You can listen to the line now and you will here that there is no bass, only treble. But it still needs something else to make it sound like radio communication, and that is a sound like background radio static. Now go to the menu option > Project and from that drop down menu select > New Audio Track. Your screen will now have a second separate audio track under your first one. For future reference you can layer several audio tracks like this one above the other and combine all sorts of separate sounds. On the new audio track but the mouse pointer directly below the end of the audio track 1, like this:
You will see a thin black line, this indicates the duration of the White Noise we are about to create in the next step. Now go to the menu option > Generate and from the drop down menu select > White Noise. You ll see a little pop up window that shows you the length in seconds of your original recording, (this is because we just clicked on audio track 2 as per the last step so we will only generate the same time length of White Noise as our original audio track).
Click the Generate button, this fills the second audio track with White Noise, perfect for Radio static. But it is too loud, so look on the left of the second audio track you will see a slider in the gray area with a Volume – & +. Move the slider practically all the way to the left, I set mine to Gain -33db. This makes the White Noise more of a background static and it doesn’t drown out the original voice line you recorded on audio track 1. You can play around with the volume slider on the second audio track to decrease/increase the white noise to obtain the effect you need ie, low volume for good radio reception, loud volume of white noise for poor radio reception.
Now go to the menu option > File > Export As > and select your choice of export type. Audacity will combine both of the audio tracks into one recording using the separate volume values you chose for the two audio tracks. You will now have one sound file with the voice line with a Radio Transmission effect.
Thanks to MindGame and Rolz for their input on this effect.