4. Two in-phase loudspeakers are some distance apart. They emit sound with a frequency of 536 Hz. A microphone is moved between the speakers along the line joining the two speakers with a constant speed of 1.60 m/s. What beat frequency is observed? The speed of sound in air is 343 m/s. Could anyone help me? I have no idea at all to solve this question since I am quite blur with the concept of beat and beat frequency also. So, could anyone explain about beat and beat frequency to me as well? Thanks.