Acoustics+Vocabulary

**ACOUSTICS VOCABULARY**

 Acoustics: is the term for the study of sound and how sound is experienced. The field of acoustics is divided into several specialist areas. The word acoustics comes from the Greek akoustikos (“to do with hearing”) and akouo (“to hear”).  Articulation Class (AC): a classification of suspended ceilings according to their ability to contribute to the acoustic privacy between work stations.

 Articulation Loss of CONSonants (%-Alcons): 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.

 Background noise (dB): for example, speech, scraping chairs, humming ventilation, traffic, machinery and equipment, sound from corridors, adjoining rooms, playgrounds. Increased background noise can have long-term negative effects, such as illness, fatigue, decreased productivity and efficiency. Therefore it is not recommended to attempt to obtain better daily speech privacy by increasing the ventilation noise, or use other sound masking systems. Another thing to bear in mind is that people are differently sensitive to sound and noise in general. Privacy and seclusion in open plan spaces can only be solved satisfactory by creating separate rooms for confidential discussions and work tasks needing higher concentration.

 Ceiling Attenuation Class (CAC): single value for the laboratory sound attenuation of a suspended ceiling between two rooms according to ASTM E 1414.

 Flutter echo: occurs when noise bounces between parallel surfaces in a room.

 Signal to noise ratio (S/N): another important parameter influencing speech intelligibility is the background noise level or, more specifically, the signal to noise ratio (S/N). This is the ratio between signal (e.g. speech) and background noise (e.g. ventilation noise). To achieve good speech intelligibility a signal is considered to be at least 15 dB above noise level. For hearing- impaired people the need is even greater; a ratio of at least 20 dB is often referred to.

 Sound insulation: the ability of a building element or building structure to reduce the sound transmission through it.