posted by elizabeth .
A student sets up two speakers spaced 2.5 meters apart, each playing the same tone of a single frequency. She stands at point P, at an equal distance from each speaker and hears the tone playing loudly. She walks towards point Q, directly opposite one speaker, and when she gets there she find the tone to be extremely hard to hear (unlike the rest of the area between P and Q). She knows that the speakers emit the sound waves in phase (so that the compressions of the waves are emitted simultaneously from each speaker), and that the speed of sound in the room is 340 m/s. What is the frequency of the sound emitted from the speakers?