Sit it in the seat! Tomtoms have the LOUDEST speakers on any gps (used almost every brand out there and have owned over 30 gps....with most being tomtoms and garmins) out there. Don't really need to look at it, but if I do, just peak down at your lap or over in the seat where it sits. Rarely use it though as my garmins handle my dirty work! But if this is your first gps, you should have one that mounts on the windshield in front of you as you wouldn't be used to how they work, etc.
V.