Acoustics_Vocabulary

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 * Sound absorption

A material's sound absorbing properties are expressed by the sound absorption coefficient, //α//, (alpha), as a function of the frequency. //α// ranges from 0 (total reflection) to 1.00 (total absorption).

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. The Articulation Class (AC) can be calculated from the interzone attenuation. 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. 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. D n,f,w (dB) Single value, according to EN ISO 717-1, for the laboratory sound insulation of a suspended ceiling between two rooms, measured according to ISO 10848-2. This measurement takes only into account the sound transmission through the suspended ceiling.
 * Articulation Class (AC)
 * Ceiling Attenuation Class (CAC)

Occurs when noise bounces between parallel surfaces in a room. 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.
 * Flutter echo
 * Speech intelligibility

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)