Instructions

Glossary
dB (decibel) – The scale on which sound pressure level is
expressed. It is dened as 20 times the logarithm of the root
mean-square pressure of the sound eld and reference pressure
(2 x 10
−5
Pa).
Direct Sound – Sound that arrives at the listener’s position directly
from the sound source, i.e. without being reected from any
objects or surface.
First Reections – Usually dened as the sound reections that
reach the listening position up to approximately 20ms after the
direct sound.
Lombard Effect – Psychoacoustic Effect named after the
French otolaryngologist Étienne Lombard observed and
reported that people with normal hearing raised their voice
when subject to noise.
Reverberation – An acoustical phenomenon that occurs in
enclosed spaces, when sound persists in that space as a result
of repeated reection or scattering from surfaces enclosing the
space or objects within it.
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Public Spaces Acoustic Treatment Guidelines / Airports