Serway & Jewett — Superposition and Standing Waves: Problem 4

Why is the following situation impossible? Two identical loudspeakers are driven by the same oscillator at frequency 200 Hz. They are located on the ground a distance \( d = 4.00 \text{ m} \) from each other. Starting far from the speakers, a man walks straight toward the right-hand speaker as shown in Figure P17.4. After passing through three minima in sound intensity, he walks to the next maximum and stops. Ignore any sound reflection from the ground.