a properly cared for gun that hasnt had someones brother's cousin's sister's boyfriend do a "trigger job" on it, will not go off unless someone sticks a body part in the trigger guard and yanks.
the mythbuster episode the stacked a bunch of sks in a circle that they modified to have super light triggers and set of some explosives near them. they got exactly ONE to go off by the shockwave of a powerful explosion.
for that to happen in a car stereo sound system it would turn anyone within 15yards to a red gooey paste. and you prolly still wouldnt set one off
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." — L. Neil Smith
The problem with being stupid is you cannot simply decide to stop doing dumb things...
"I crapped my pants to avoid the draft!!" -Ted Nugent