Trane TRG-TRC007-EN manual Glossary

Glossary

absorbed sound Sound energy that strikes a material and is converted from sound energy to heat energy within the material.

absorption coefficient The ratio of the sound energy absorbed by the material to the total sound energy incident upon the surface of that material.

AMCA Air Movement and Control Association International (www.amca.org)

ARI Air-Conditioning & Refrigeration Institute (www.ari.org)

ASHRAE American Society of Heating, Refrigerating and Air Conditioning Engineers (www.ashrae.org)

attenuation The reduction in the sound level as it travels along the path from a source to the receiver.

A-weightingA single number used to describe sound. It uses weighting factors, by octave band, to approximate human response to sound in the range where no hearing protection is needed. It is most appropriately used for low- volume (or quiet) sound levels and is expressed as dBA.

broadband sound Sound energy that occurs at many frequencies, usually covering the entire audible range.

center frequency Single frequency used to identify an octave band. It is calculated by taking the square root of the product of the lowest and highest frequencies in the octave band.

decibel (dB) A dimensionless ratio of two quantities that is used to describe both sound power and sound pressure. It is defined as ten times the logarithm to the base ten (log10) of the measured quantity divided by the reference quantity.

dynamic insertion loss The sound insertion loss of a duct silencer with air flowing through it.

free field A homogeneous, isotropic medium, free from boundaries. An example of a free field over a reflecting plane would be a large open area void of obstructions, like a parking lot or meadow.

free-field method A common method for testing HVAC equipment that is too large to be tested in a reverberant room, such as water chillers and cooling towers. The equipment is placed on a hard surface on a large parking lot outdoors to approximate the sound conditions in a free field above a reflecting plane. The sound pressure waves travel evenly in a hemispherical pattern away from the equipment. Sound-power levels are determined by measuring sound- pressure levels on an imaginary hemispherical surface surrounding the equipment.

frequency The number of cycles, or oscillations, per second of a wave in periodic motion. Expressed in hertz.

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