So much for basic picture/sound synchronising. What about the other associated background sounds? You will need to use another track for background traffic noises. It is not a precise effect — the roar is the same all the time, so it can be joined in level with the first frame of picture. So, wind back to the first frame of picture and take another look at the synchroniser. You have the cutting copy starting in the track nearest to you, the track of the car stopping in the next track and spacing in the other two tracks. You want the traffic roar to start where the scene starts, so wind back and, joining on the left of the synchroniser, peel the join of the spacing to the third of the leaders and join on the background traffic sound in place of the spacing. You can then wind on again and check your joins. You should find that the start of the picture, the start of Track 1 and the start of the background traffic sound are all parallel in the synchroniser. Spacing remains on the last track. You do not need any more sounds for the first shot so you can wind down.