What acoustic impedance is
Acoustic impedance describes how much a medium resists the passage of sound. It depends only on the medium’s density and the speed of sound within it, and it determines how much sound is reflected versus transmitted when crossing a boundary between two materials (important in ultrasound imaging, sonar, and audio engineering).
The formula
Acoustic impedance is Z = ρ × c, where ρ is density and c is the speed of sound in that medium. At a boundary between two media, the intensity reflection coefficient is R = ((Z2 – Z1) / (Z2 + Z1))², and the transmission coefficient is T = 1 – R.
This calculator is for general physics reference and educational use.
Last reviewed August 2026