Acoustics_Vocabulary

=Acoustics: is the term for the study of sound and how sound is experienced and is divided into several specialist areas.= = = =Articulation Class (AC): 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. This can then be used as a tool to classify and compare acoustic ceiling systems. The higher the AC the better the speech privacy in an open plan situation. We recommend that you use a suspended ceiling with minimum Articulation class 180 in order to achieve acceptable speech privacy. A high Articulation Class gives some privacy, a lower Articulation Class means lower privacy. Confidential conversation and work tasks demanding concentration need good privacy.= = = =Noise Reduction Coefficient (NRC): Single value for sound absorption according to ASTM C 423, derived as the mean value of 4 frequencies in the range 250-2000 Hz.= = = =Reverberation time, (T or RT): The time it takes for the sound pressure level to fall by 60 dB after the sound has been turned off. Measuring the reverberation time allows us to calculate the total sound absorption. The reverberation time varies according to the frequency.= = = =Sabine: 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).= = = =Sound insulation: 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, Dn,f,w, Rw or R'w. Impact sound insulation is expressed by a single value Ln,w or L' n,w .= = = =Sound pressure level (dB): The pressure variations caused by sound waves in air are called sound pressure. The lowest sound pressure level which can be heard is 0 dB, known as the hearing threshold. The highest level which can be tolerated is called the pain threshold and is around 120 dB.= = = =Speech intelligibility: Speech intelligibility is directly dependent on the level of background noise, reverberation time and the shape of the room. Different methods are used to evaluate speech intelligibility, the most common ones are RASTI, STI and %-Alcons.=