Even the body components of a microphone can create obstacles to high frequency sound waves. When waves that are odd fractions of a wavelength out of phase meet, the actual shape of the sound wave is altered. This results in one kind of distortion. When sound meets with a large surface the sound may be absorbed or reflected depending on the nature of the surface. Refraction is the change of direction of a wave as it passes from a medium of one density to a medium of another density.
Different temperatures can cause layers of air to have different densities.
This often happens out of doors at sunset. The result is that sounds travel farther. This is why sounds do not travel so far on a hot summer's day. Noise may be defined as an unwanted sound. A sound engineer is concerned with two sorts of noise system noise , introduced by microphones, amplifiers, tape recorders, etc.