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 Waves. The speed of a wave depends on the elastic and inertia properties of the medium through which it travels. When a wave encounters different medium where the wave speed is different, the wave will change directions.
The study of sound properties (especially reflections) is called acoustics. Waves â Sound and Light Slide 5 Refraction The change of speed in different mediums can bend a sound wave if it hits the different medium at a non-90Â° angle. This is called refraction. The wave bends toward a slower medium or away from a faster medium.