A
Rayl,
rayl or
Rayleigh is one of two units of
specific acoustic impedance or, equivalently,
characteristic acoustic impedance; one an
MKS unit, and the other a
CGS unit. The units are named after
John William Strutt, 3rd Baron Rayleigh, and not to be confused with the
rayleigh unit of
photon flux, used to measure
airglow, and named after his son,
Robert John Strutt, 4th Baron Rayleigh. It has the same dimensions as momentum per volume.