Acoustics_Vocablourary

Classification of sound absorbers into Sound Absorption Classes A-E, according to EN ISO 11654, including frequencies 200-5000 Hz.
 * Absorption Class **

A classification of suspended ceilings according to their ability to contribute to the acoustic privacy between work stations. AC is calculated from the Interzone Attenuation according to ASTM E-1110.
 * Articulation Class (AC) **

One method of objectively measuring speech intelligibility is Articulation Loss of CONSonants (%-Alcons), showing the number of consonants being missed as a percentage. Consonants play a much more significant role in speech intelligibility than vowels. If the consonants are heard clearly, the speech can be understood more easily.
 * Articulation Loss of CONSonants (%-Alcons) **

Single value for the laboratory sound attenuation of a suspended ceiling between two rooms according to ASTM E 1414. This measurement takes only into account the sound transmission through the suspended ceiling.
 * Ceiling Attenuation Class (CAC) **

Single value for sound absorption according to ASTM C 423, derived as the mean value of 4 frequencies in the range 250-2000 Hz.
 * Noise Reduction Coefficient (NRC) **

RASTI is an objective way of measuring speech intelligibility. It is measured at two frequencies, 500 and 2000 Hz, by placing a loudspeaker, which transmits sound from the location of the person speaking, and a microphone where the listeners are situated. (See also STI).
 * Rapid Speech Transmission Index (RASTI) **

The physicist Wallace Clement Sabine (1869-1919) created in Riverbank, west of Chicago, the well known Sabine formula (T=0,16V/A), showing the relationship between reverberation time (T s), room volume (V m³) and the amount of absorption (A m²).
 * Sabine **

The ability of a building element or building structure to reduce the sound transmission through it. The sound insulation is measured at different frequencies, normally 100-3150 Hz. Airborne sound insulation is expressed by a single value, //D//n,c,w, //R//w or //R'//w. Impact sound insulation is expressed by a single value //L//n,w or //L'// n,w.
 * Sound insulation **

Similar to the RASTI method but a more complete form of measuring speech intelligibility by measuring all octave bands in the frequency range 125-8000 Hz.
 * Speech Transmission Index (STI) **