acoustic+vocabulary

=**//__Acoustic vocabulary. __//**=

·__Absorption Class__: Classification of sound absorbers into Sound Absorption Classes A-E, according to EN ISO 11654, including frequencies 200-5000 Hz.

·__Acoustics__: The study of sound. In everyday language also refers to how sound is perceived in particular premises. Background noise (dB) For example, speech, scraping chairs, humming ventilation, traffic, machinery and equipment, sound from corridors, adjoining rooms, playgrounds.

·__Ceiling Attenuation Class__: (CAC) 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.

·__Flutter echo__: Occurs when noise bounces between parallel surfaces in a room.

·__Noise__: Unwanted sound. Noise can often be the individual perception of a particular sound, e.g. a background noise.

·__Privacy__: Acoustic privacy between working places in open plan offices is expressed with the Articulation Class (AC).

·__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.

·__Sound absorbers__: Materials and structures with the ability to take up sound energy and convert it into other forms of energy. They improve room acoustics by removing sound reflections, thus reducing the noise and the reverberation time.

·__Sound absorption__: Means that sound energy is converted into mechanical vibration energy and/or heat energy. Sound absorption is expressed as the sound absorption coefficient α or the sound absorption class (A-E) according to EN ISO 11654 or NRC/SAA according to ASTM C 423.

·__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,c,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.

·__Speech Transmission Index__ (STI): 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