2 [pt] An omni-directional speaker sits in the middle of a room, playing a 440 Hz tone (this is the reference 'a' often used for tuning instruments). The speaker emits 10W of power. a) Write down an equation for the pressure amplitude in the air as a function of time and distance from the speaker 1". (Remember that the energ}r spreads out as the wave travels away, so A will depend on Ag the amplitude at distance 1 away, r). The speed of sound in air is around 300 m/s. b) A musician sits 3m away from the speaker. What is the sound intensity at this distance? c) Estimate the size of the sound-collecting surface of the musician's two ears. Use this to find the power the musician hears. d) Active noise cancelling headphones play sound to cancel out incoming waves. i) Explain how this works with the principle of superposition. ii) If our musician put on noise cancelling headphones, what would the pressure wave it crates have to look like to cancel the sound from the speaker? Write down an equation for pressure as a function of time generated by the head- phones