Conceptual Questions Chap. 14

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Conceptual Questions Chap. 14

• A crude model of the human throat is that of a
  pipe open at both ends with a vibrating source to
  introduce the sound into the pipe at one end.
  Assuming the vibrating source produces a range of
  frequencies, discuss the effect of changing the
  pipes length.
• Explain how the distance to a lightning bolt can
  be determined by counting the seconds between the
  flash and the sound of thunder.
• By listening to a band or orchestra, how can you
  determine that the speed of sound is the same for
  all frequencies?
• A soft-drink bottle resonates as air is blown
  across its top. What happens to the resonant
  frequency as the level of fluid in the bottle
  decreases?

The resonant frequency depends on the length of
the pipe. Thus, changing the length of the pipe
will cause different frequencies to be emphasized
in the resulting sound.
The speed of light is so high that the arrival of
the flash is practically simultaneous with the
lightning discharge. Thus the time delay between
the flash and the arrival of the sound of thunder
is the time sound takes to travel the distance
between the lightning bolt and you. Knowing the
speed of sound in air, this information gives you
an estimate of the distance to the lightning
bolt.
If the speed of sound depended on frequency, then
the sounds with different frequency could reach
your ear at different times, creating a jumble of
noise instead of well-timed music.
As the length of the air column increases (fluid
level decreases), the resonant frequency
decreases.