There is a microphone, but only at turn 5, and only on the passenger side of the vehicle.
Laguna Seca is more than a racetrack, its a "natural" area that has hiking trails, camp grounds, etc.
There are a couple effective ways people have worked around this constraint. You can either just let out of the throttle in Turn 5, or you can "fashion" some exhaust extensions that turn your tail pipes towards the drivers side of the car. Obviously the first option is the easiest, but I saw some creative, temporary exhaust mods on some cars when I tracked there years ago.