One sound source is at the origin and the other is at 9.0m}. They emit sound of the same frequency in phase. "When an observer starts at the origin and walks in the positive xdirection they encounter four locations where they experience constructive interference of sound waves. The rst one is at I = 0.521m. 18. The speed of sound in air is 340%. What is the frequency of the emitted waves? {a} 15211:: (b) *** 162Hz (c) 1T2Hz (d) ISZHZ (e) 192Hz 19. If the observer instead walks from the origin to 9.01mi how many times will they encounter destructive interference (a) [1 times {b} 1 times {c} *** 2 times {d} 3 times (e) 4 times