Physics of Sound 301
HOMEWORK ASSIGNMENT #3
Due Friday Feb 11, 2005
RMW refers to the textbook The Science of Sound, 3rd
Edition, by T.D. Rossing, F.R. Moore, & P.A. Wheeler
Use 343 m/s for the speed of sound.
- RMW, page 58, exercise 2.
- Suppose you listen to sound from two loudspeakers at a distance of
6 m from one and 4.8 m from the other. What are several wavelengths and the
corresponding frequencies for which you will experience constructive
interference? What are several wavelengths (and frequencies) for which the
interference is destructive?
- Speakers A and B are vibrating in phase. They are directly facing each
other, are 7.80 m apart, and are playing a 73.0 Hz tone. On the line between
the speakers there are three points where constructive interference occurs.
What are the distances of these three points from speaker A?
- A musician standing close beside a railroad track hears the whistle
blowing while a train passes her. She reports that the pitch dropped by
the musical interval called a major third. As we shall learn later, this means
the received frequency must have been about 12% higher as the train approached
(and 12% lower as it receded) than the frequency that would have been heard
with the train at rest. How fast was the train going?
- You wish to ensure that the diffraction angles for the mid and high
frequency cones on a loudspeaker are the same. Find two values for the
diameters of these cones that will satisfy this requirement. Assume that
the cones emit sound with frequencies of 500 Hz (mid frequency range) and
5000 Hz (high freq. range). (Note that there are many possible solutions
to this problem - try to find values that are reasonable.)