| Term | Definition |
| Decibel (dB) | The decibel is a relative unit of measurement used widely in acoustics. It is a logarithmic unit describing the ratio between a measured level and a reference value.
One common ratio to AV people is Sound Pressure Level (SPL). Weightings are applied to sound pressure scales to reflect the performance of the human ear under certain conditions. Most typically encountered are:
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| Acoustic Consultant | Professional with specialist skills and experience in acoustics, usually commissioned to advise on the physical acoustics within a space/building and the noise and vibration issues associated with the construction process. |
| Designer/AV Designer | The professional or technical specialist with responsibility for designing the electronic and electroacoustic (PA) systems and coordinating with other members of the design team. May be employed by the organisation or an external consultant.
AV designer may also have responsibility for leading electroacoustic scope, where briefed. |
| Intelligibility | Speech intelligibility is a rating of how comprehensible speech is in a given environment. |
| Mix-Minus | An electro-acoustic system that is zoned and routed in such a way to allow microphones from one user to be routed to the speakers of other users for local voice lift functionality |
| Reverberation Time (RT60) | The reverberation time of an enclosure, for a sound of a given frequency or frequency band, is the time that would be required for the reverberantly decaying sound pressure level in the enclosure to decrease by 60 decibels |
| Signal to noise ratio | The difference between the measured sound level and the noise floor (all other sources). Expressed in dB |
| STI | The Speech Transmission Index (STI) is an objective metric ranging between 0 and 1 representing the transmission quality of speech with respect to intelligibility by a speech transmission channel |