C

Ceiling Attenuation Class (CAC)
A laboratory derived rating for this sound attenuation of a suspended ceiling system over two adjacent rooms sharing a common plenum.

Clarity Factor (C80)
Expressed in decibels it is the ratio of the early acoustical evergy (0 to 80 ms) to the late reverberant energy (80 to 3,000 ms)

Coincidence dip
The effect produced by an incident sound on a panel when the wavelength of sound equals wavelength of the bending wave in the panel. The frequency at which this occurs is called coincidence frequency.

Colouration
The noticeable change in sound quality that occurs when a signal passes through an imperfect transmission system such as enclosed space or a sound reproduction system

Critical frequency
The lowest frequency at which the coincidence dip occurs