since you drive an '01 celica this noise can likely be your rotors.
if your brake pads have worn off, you are probably stopping yourself with your rotors (not good) and this will make a crunching noise. if it has been going on for a while, you will need to replace both your pads and your rotors.
This has happened to me in my 2000 Celica. My rear rotors and pads were shot. I had an initial crunching sound and then later a more severe terrible grinding and squealing noise. I replaced the back rotors and pads first and later the front rotor and pads because they were on their way out too. I believe the front rotors were around $180-220 and pads $40-60. Similar for the rear. Install is easy and could be done yourself with some tools and a little bit of mechanical aptitude. I wish I did them myself. I think install for the fronts was $60-80 and more for the rear because I made the mistake in having Toyota do it.