Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Acoustic impedance is a measure of how much resistance an acoustic wave encounters as it travels through a medium. It is defined as the product of the density of the medium and the speed of sound in that medium.
5 Must Know Facts For Your Next Test
Acoustic impedance ($Z$) is given by $ Z = \rho c $, where $\rho$ is the density of the medium and $c$ is the speed of sound in that medium.
It plays a crucial role in determining how much ultrasound is reflected or transmitted at the boundary between two different media.
The unit for acoustic impedance is Rayl (kg/(m^2·s)).
A large difference in acoustic impedance between two media results in a higher reflection coefficient, meaning more sound waves are reflected rather than transmitted.
Matching layers are often used in ultrasound transducers to minimize impedance mismatch and maximize energy transfer.
The ratio of the reflected wave amplitude to the incident wave amplitude at a boundary between two different media.
Transmission Coefficient: The ratio of the transmitted wave amplitude to the incident wave amplitude when an acoustic wave passes from one medium into another.