The two speakers at S1 and S2 are adjusted so that the observer at O hears an intensity of 6 W/m2 when either S1 or S2 is sounded alone. The speakers are driven in phase (at the speakers) with various frequencies of sound. The distance between the two speakers is L = 4 m and distance between S1 and the observer is also L = 4 m. Assume that the speed of sound is 335 m/s. Suppose both speakers are driven a frequency f = 30 Hz. Required:
What is I, the intensity of the combined wave at the observer?