Basic Documentation

Glossary
This glossary describes various terms and acronyms used in this application guide. For a
comprehensive listing of building control terminology, see the Technical Glossary of Building
Controls Terminology and Acronyms (125-2185).
A-Weighted Sound Level
A single number in dB that represents the effect of all frequencies of a given sound on the
human ear. Since human hearing is less sensitive to very low and very high frequencies, the
contribution of these is reduced in terms of the resulting sound level to provide an A-weighted
value. Sound level meters typically also provide an A-Weighing sound measurement feature.
This approach is typically used to measure ambient sound levels in conjunction with
compliance with allowable noise exposure limit regulations. However, using the A-Weighted
approach is not recommended for analyzing lower sound levels for the purpose of achieving
a proper balanced room ambient sound level.
Also see C-Weighted Sound Level.
anechoic termination
A device used in acoustical laboratories at the end of a test duct in conjunction with
determining certified sound power ratings for HVAC equipment. The anechoic termination
prevents excessive end reflection of the sound waves back into the test duct where they
would interfere with the waves generated by the piece of equipment being tested. Also see
End Reflection.
acoustics
The science of sound, its measurement and its control.
acoustical louver
A specific type of louver used in air transfer openings between rooms to reduce sound
transmission through the louver.
airborne sound
Sound waves that travel through the atmosphere as opposed to sound that travel through
elements of a building structure (such as, pipes, beams, walls, floors, etc.).
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