Two automobiles are equipped with the same single-frequency horn. When one is at rest and the other is moving toward an observer at 13 m/s, a beat frequency of 5.8 Hz is heard. What is the frequency the horns emit? Assume T = 20°C. I understand that this is related somehow to the doplar effect. I thought to use the equation to find the heard velocity when a sound is moving towards a listener which is... Frequency Heard = Frequency Sound (Velocity of Sound/(Velocity of sound- velocity of moving sound) This formula should work, but i am wondering if i can assume beat frequency is the actual frequency of the sound. I feel as though it is not. I need to know how to use this beat frequency to find the actual frequency of the sound. HELP!