試題詳解

3. Two speakers both produce sound wave of power = 400πWatt, frequency = 170 Hz, and sound velocity = 340 m/s. They act as point sources and propogate in all directions. The output of the two speakers are synchronized and have the same phase. They are placed at different locations and the distances between the speakers and the observer P are d₁ = 10 m and d₂ = 5 m, respectively. What is the intensity of the sound wave detected by the observer? (The effect of interference should be considered.)
(A) 1 W/m²
(B) 2 W/m²
(C) 3 W/m²
(D) 5 W/m²
(E) 9 W/m²