The acoustic field in a standing wave tube is given by aexp(ia-ikx)+bexp(iar tikx) where the incident wave has an amplitude of a=10 pa. the fluid in the tube is air and at the end of the tube there is an interface with a fluid that has a characteristic impedance of pc-560 rayls. what is the magnitude of the reflected wave b, and what is the difference in level between the reflected wave and the incident wave in db?