Chapter 132 Sound Intensity and Resonance

1
Chapter 13-2 Sound Intensity and Resonance

• Objectives
• The student will
• Calculate the intensity of sound waves.
• Relate intensity, decibel level, and perceived
  loudness.
• Explain why resonance occurs.

2
Sound Intensity

• Intensity is the rate at which energy flows
  through a unit area perpendicular to the
  direction of wave motion.

3
Sound Intensity

• What is the intensity of the sound waves produced
  by a trumpet at a distance of 3.2 m when the
  power output of the trumpet is 0.20 W? Assume
  that the sound waves are spherical.

4
Sound Intensity

• Given
• P 0.20 W
• r 3.2 m
• Unknown
• Intensity ?

5
Sound Intensity
Intensity and frequency determine which sounds
are audible.
6
Sound Intensity
Relative intensity is measured in decibels.
7
Sound Intensity
8
Forced Vibrations and Resonance

• Vibration at the natural frequency produces
  resonance.
• Resonance is a condition that exists when the
  frequency of a force applied to a system matches
  the natural frequency of vibration of the system.

9
Forced Vibrations and Resonance

• The human ear transmits vibrations that cause
  nerve impulses.