1. A sound wave with frequency f = 2300Hz is sent into a circular tube of radius R=160cm through an opening at some point A. A receiver lies at point B, separated from A by an angle α=130°. The speed of sound in air is v=330 m/s. Sound propagates from A to B in both directions along the tube. (a) What level of interference do you observe at B? (b) What happens if the frequency is lowered to f1=230 Hz? (c) And to f2= 23Hz? 2. I guess, I have to calculate the periphery of the circle with given R, and hence divide Δx with λ, which would give me n. If its closer to a whole number, it would result in a constructive interference. With questions (b) and (c), my guess is, that it does not change the level of interference, since 230 and 23 are multiple integers of 2300 (factor 10).