Acoustics_Vocabulary

** 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.

 **Dn,c,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 140-9. 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.

 **Rapid Speech Transmission Index (RASTI)** 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).

 **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).(image): (Sabine's formula)

 **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.