Plumbing trap type?

i need what i think is a u-trap or p-trap. it should be equal length on both sides and pvc material. not using it for plumbing but to assist my students with their pitch matching when singing in class. one end is held at the mouth and the other held up to the ear. it sounds crazy but really works. i purchased... show more i need what i think is a u-trap or p-trap. it should be equal length on both sides and pvc material. not using it for plumbing but to assist my students with their pitch matching when singing in class.

one end is held at the mouth and the other held up to the ear. it sounds crazy but really works. i purchased these once before at a hardware store but don't remember exactly what they are called. can someone who knows plumbing materials tell me what it is called and where i can buy them about 30 or them?
Update: where can i purchase them online? didn't see them at the home depot website when i entered p-trap.
Update 2: i looked up s-trap and that's not it. the shape is like the letter c (a semi-circle maybe)
8 answers 8