Acoustics


 * Speed:** Distance travelled in unit time (m/s)

**Frequency:** Number of complete waves in one second (Hz)

**Wavelength:** Distance between matching points on the wave (m)

**Longitudinal:** Vibration parallel to direction of travel

**Transverse:** Vibration at right angle to direction of travel

Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations

Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. During propagation, waves can be reflected, refracted, or attenuated by the medium.

The behavior of sound propagation is generally affected by three things:


 * A relationship between density and pressure. This relationship, affected by temperature, determines the speed of sound within the medium.


 * The propagation is also affected by the motion of the medium itself. For example, sound moving through wind. Independent of the motion of sound through the medium, if the medium is moving, the sound is further transported.


 * The viscosity of the medium also affects the motion of sound waves. It determines the rate at which sound is attenuated. For many media, such as air or water, attenuation due to viscosity is negligible.

Room acoustics are about the way in which sound behaves in a room. Sound transmission, sound absorption, sound reflection and sound diffusion are all aspects that are important here. Room acoustics also include how we as humans perceive different acoustic phenomena. The field of building acoustics covers sound insulation too, where the route that the sound takes from the room to other areas is included

As regards acoustic design, it is an advantage if different designs and procedures can be evaluated objectively. For this purpose, a number of measurable room acoustic descriptors have been defined. These descriptors can be used to formulate room acoustic specifications and to check the effect of different procedures. It would, of course, have been an advantage to have only one descriptor that works in all rooms. But hearing is multidimensional, so several descriptors are required.