The easiest way is to press shift+8 for the "free train view" while in the cab. This view uses the exterior sounds without the interior muffling, but it'll be more shaky because the camera will be anchored to the unsprung loco centre point instead of the body. The sound samples themselves are also muffled and of somewhat poor quality, but sadly improving them is beyond my audio editing skills.
You'll need to hold down B and E simultaneously to exit the shutdown position. The instructions or the on-screen helper don't seem to indicate this well enough since you're not the only one to have had difficulties with the brakes. I'll need to figure out a way to make it simpler.