Issues in calibration. Primary reference standards. A reference standard for a unit of measurement is an artifact that embodies the quantity of interest in a way that ties its value to the reference base. At the highest level, a primary reference standard is assigned a value by direct comparison with the reference base.
Refraction of Sound. Refraction is the bending of waves when they enter a medium where their speed is different. Refraction is not so important a phenomenon with sound as it is with light where it is responsible for image formation by lenses, the eye, cameras, etc. But bending of sound waves does occur and is an interesting phenomena in sound.
Noun. 1. refraction-the change in direction of a propagating wave (light or sound) when passing from one medium to another. physical phenomenon-a natural phenomenon involving the physical properties of matter and energy. birefringence, double refraction-splitting a ray into two parallel rays polarized perpendicularly.