Acoustic Impedance⚠ unverified
Physics / Acoustics · Compute the specific acoustic impedance
Parameters
| Input | Symbol | Unit | Default | Description |
|---|---|---|---|---|
| rho | ρ | kg/m**3 | 1.0 | Medium density |
| c | c | m/s | 1.0 | Speed of sound |
| Output | Symbol | Unit | Description |
|---|---|---|---|
| result | Z | Pa*s/m | Specific acoustic impedance, in pascal-seconds per metre (Pa*s/m) |
The science & history
Understanding the Parameters
-
$\rho$, $c$ — stiffer/denser media have higher $Z$ (water ≫ air), causing strong reflections at interfaces (e.g. air–water).
-
$Z$ — also appears in $I = p_{\mathrm{rms}}^{2}/Z$ (Sound Intensity).
Derivation (Approaching a Proof)
From the 1-D wave equation / linear acoustics, plane progressive waves satisfy $p = \rho c\, u$ for the appropriate sign of travel direction. The ratio $Z_0 = \rho c$ is the characteristic impedance. (Mechanical acoustic impedance of a surface is $p/U$ with volume velocity $U$ — related but not identical.)
History
Characteristic impedance is standard in wave acoustics and underwater sound; the rayl unit honours Lord Rayleigh.
Related Concepts: Sound Intensity, Speed of Sound in Air, Speed Of Sound, Sound Pressure Level
Notes: Registry calculator acoustic-impedance (unverified). Characteristic $Z=\rho c$ only.