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.
So there you have it sound does travel faster in warm air BUT it may appear to travel farther in cold air. This is how that worksâ¦. â¦if the air close to the ground is colder than the air above it then sound waves travelling upwards will be bent downwards. This is called Refraction.