How do I...?

I have a mono video camera, and I shoot some video of trains passing by, I would like to “synthesize” the mono track into stereo, and make it sound like the audio is “panning” with the train, say from left to right.
In other words make the sound follow the train.
I shot one the other day, as the locomotive(s) pass by, the audio, as I am hearing it, goes into doppler shift but there is still audio in both ears as the cars pass, so as the locomotive passes, I would like to pan the locomotive audio while maintaining a
a decent level on both channels as the cars pass, of course timing is critical, any ideas?, does anyone else understand my question, I am not sure I do LOL. Of course the easy answer is to record the audio in stereo but I do not have that capability…yet.

You will need 2 mono tracks, so select the track and make a duplicate copy with Ctrl+D

Set the man position of one of the tracks all the way to the left, and the pan position of the other all the way to the right.

Since you recorded this from a fixed point, you do not have to worry about the sound getting louder as it approaches and quieter as it goes away, and the Doppler effect is taken care of as well. This makes it much easier.

Listen to the recording and try to identify the exact moment where the train is right in front of you. It may be worth adding a label at this point (Ctrl+B)
Now use the “Envlope” tool to adjust the volume of each track to create the pan effect.

Click on picture to view full size

That’s what I call service, I knew it could be done, but I haven’t used audacity in a while and forgot what to do, thanks so much! I will give it a try.

Just out of curiosity I’ve made a fully synthesized example - a weird kind of futuristic space train going past.

Since this was synthesized from scratch, I had to also synthesize the Doppler shift (using the time track in Audacity 1.3.5), and also added some reverb (freeverb) and progressively filtered it so that the high frequencies were attenuated when the “train” was at "distance.

The sound was entirely created in Audacity 1.3.5 (with the aid of a few plug-ins from the plug-in pack available from the main Audacity web site).
The forum does not allow attachments of mp3’s, so the attached file is the mp3 zipped. (153 KB)

That was an interesting proof of concept. In the videos I have shot after I process them in my video editor (Magix MEP14 trial) I save them as a mpeg this allows me to strip the audio out of the video, (ungroup objects)then I can open the mp3 in another program (Audacity) edit it to my liking then regroup it with the visual object.
When I get that done on the latest video I will post a you tube link here, of course that is assuming everything works.
Thanks again!