Question

6. An airhorn is essentially a tube of air that vibrates at certain resonant frequencies, just like many musical instruments. The following questions refer to two airhorns, each 85.0 cm long, operating in the same still air (no winds, same temperature, etc.), where the speed of sound is 340 m/s. Horn 1 is a tube that is open at both ends. Horn 2 is a tube that is open at one end but closed at the other. a. Evaluate (T/F/N) the following statement, and explain your reasoning fully. When horn 1 produces a standing sound wave that has 3 pressure antinodes, that sound is one octave higher in pitch (frequency) than when horn 2 produces a standing sound wave with 2 pressure antinodes. b. Suppose that horn 1 is located at the origin (0, 0), horn 2 is at (100, 0), and you’re standing at (75, 0). All coordinates here are given in meters. You are holding a sound meter, and when each horn is sounded by itself, you get these readings: Horn 1: 76.0 dB Horn 2: 92.0 dB Find the ratio of the two horns’ power outputs. That is, calculate P1/P2. (For this portion, assume no echoes or other complications.) c. Now suppose you discard horn 2. Then you hold horn 1 and walk at a steady speed of 2 m/s directly toward a tall vertical wall that echoes readily. Calculate the beat frequency you will hear if horn 1 is sounding its fundamental frequency.

Answer 1