What is the function of a reed in a woodwind instrument

Without the reed on the woodwind instruments no sound would come out. This si because i may be wrong but I am in band so i believe this is correct. That the reed vibrates against the head joint and that makes the music comes out at the end, like I said i may be wrong because I am a brass player, but I hope this helps!

H=   2(area/a+b)h= 2(144/a+b)h= 2(144/18+18)h= 2(144/36)h= 2(4)h=8