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.
Refracting is the phenomena that takes place when sound waves are  reflected from a surface along parallel lines. During this  phenomena the phase velocity of the wave chang â¦ es but the frequency  of the wave stays the same. 4 people found this useful.