When sound waves contact a room surface such as a ceiling, wall or floor, a portion of the sound energy is reflected back into the room, and the rest is considered to be absorbed primarily by conversion into heat due to friction within a porous material, or by vibration of a solid material.

Acoustical Material

 Any material that affects the sound level or direction of travel of a sound wave. Some acoustical materials are specifically characterized as sound absorbers, or sound reflectors, or as barriers to sound passage.

Ambient Noise

The lowest background noise level in a space.

Ceiling Attenuation Class (CAC)

 A measure for rating the performance of a ceiling system as a barrier to airborne sound transmission through a common plenum between adjacent closed spaces such as offices. A ceiling system with a CAC < 25 is consider low performance, whereas one with CAC > 35 is high performance.

Frequency

The repetition rate of a sound wave measured in cycles per second, which is usually expressed in Hertz (Hz). The audible frequency range for normal hearing individual spans from 20Hz to 20 kHz. Frequency is that characteristic of a sound which is perceived by a listener as the “pitch”.

Leed

It is a green building certification system that was developed by the U.S. Green Building Council (USGBC) in March 2000. LEED provides building owners and operators with a framework for identifying and implementing practical and measurable green building design, construction, operations and maintenance solutions.

NRC

Average sound absorption coefficient measured at four frequencies: 250, 500, 1,000, and 2,000 Hz Rates the ability of a ceiling or wall panel or other construction to absorb sound. NRC is the fraction of sound energy, averaged over all angles of direction and from low to high sound frequencies, that is absorbed and not reflected. NRC ranges from 0 (concrete floor) to 1.00.