Physics A: Problem Set 12: The nature of sound

homework

1. What range of sound wavelengths in air at standard temperature and pressure (0 °C and 1 atm) are audible to a human with ideal hearing?
   1. What is the wavelength near the lower limit where f ~ 20 Hz?
   2. What is the wavelength near the upper limit where f ~ 20 kHz?
2. The pitch used by orchestras for tuning is a concert A with a frequency of 440 Hz (listen if you wish).
   1. What is the period of this note?
   2. What is the speed of sound in air if the wavelength of this note is 78 cm?
3. To the nearest second, how many seconds elapse between when a flash of lightning is seen and when the clap of thunder is heard if the lightning is…
   1. 1 kilometer away?
   2. 1 mile away (1.6 km away)?

classwork

4. A measurement, a calculation, and a set of related questions.
   1. Measure the horizontal distance between your ears. (This is not easy to do. You will probably be off by a couple of centimeters, but that is OK. An approximate value is sufficient.)
   2. Approximately how long does it take a sound wave coming from a source on one side of your head to travel the distance between your ears? (This is known by audiologists as the interaural time difference or ITD.)
   3. What would happen to the value calculated in part b. if the source of sound was moved forward a bit (not closer to your ear, but in the direction you call forward — anterior, as they say in the medical professions)?
   4. What would happen to the value calculated in part b. if the source of sound was directly in front of you instead of off to one side?
   5. Your brain can actually perceive the interaural time difference (as long as you have two working ears). What does your brain use this information for?