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🔋college physics i – introduction review

Acoustic Wave

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

An acoustic wave is a mechanical disturbance that propagates through a medium, such as air, water, or a solid material, by the vibration of particles within that medium. These waves carry energy and can be used for various applications, including hearing, sonar, and ultrasound imaging.

5 Must Know Facts For Your Next Test

  1. Acoustic waves can be classified as either longitudinal or transverse, depending on the direction of particle vibration relative to the wave propagation.
  2. The speed of an acoustic wave in a medium is determined by the properties of the medium, such as density and elasticity.
  3. Acoustic waves can be reflected, refracted, and diffracted when they encounter boundaries or obstacles in their path.
  4. The intensity of an acoustic wave decreases with distance due to absorption and spreading, following an inverse square law.
  5. Acoustic waves can be used to measure properties of a medium, such as temperature, density, and composition, through techniques like ultrasound imaging and sonar.

Review Questions

  • Explain how the properties of a medium affect the propagation of an acoustic wave.
    • The properties of the medium, such as density and elasticity, directly influence the speed at which an acoustic wave propagates. A medium with higher density and stiffness will generally allow the acoustic wave to travel faster. Additionally, the impedance of the medium, which is the resistance to the flow of the wave, depends on the medium's properties and can affect the reflection, refraction, and absorption of the acoustic wave as it travels through the medium.
  • Describe the differences between longitudinal and transverse acoustic waves, and provide examples of each.
    • Longitudinal acoustic waves are characterized by the particles in the medium vibrating parallel to the direction of wave propagation, while transverse acoustic waves have the particles vibrating perpendicular to the direction of propagation. Longitudinal waves are commonly observed in sound waves traveling through air or water, where the particles oscillate back and forth in the same direction as the wave. Transverse waves, on the other hand, are more commonly associated with waves traveling through solid materials, such as the shear waves generated by earthquakes.
  • Discuss the role of acoustic waves in the process of hearing, and explain how the properties of these waves contribute to our ability to perceive sound.
    • Acoustic waves play a crucial role in the process of hearing. When sound waves, which are a type of acoustic wave, enter the ear, they cause the eardrum (tympanic membrane) to vibrate. These vibrations are then transmitted through the middle ear bones (ossicles) and into the fluid-filled inner ear, where they stimulate the hair cells in the cochlea. The hair cells then convert the mechanical vibrations into electrical signals that are sent to the brain, allowing us to perceive and interpret the sound. The properties of the acoustic waves, such as their frequency and amplitude, directly influence the way we perceive the characteristics of the sound, such as pitch and volume. The ability of the ear to detect and process a wide range of acoustic wave frequencies is a remarkable feat of human physiology.