Basic Documentation

Terminal Equipment
Noise Problem Potential Remedy
Excessive Room Supply Air Diffuser Sound
This is usually a higher pitched whistling sound caused
by a high pressure drop across air diffusers. (Ensure the
problem is the diffuser by removing it and noting if a
substantial reduction in the sound level occurs.)
• Ensure that the flexible duct at the connection to the
diffusers is in relatively good vertical alignment. The
connecting duct should be relatively straight for 1 to 2
duct diameters immediately prior to the diffuser collar.
• Where multiple diffusers serve a space, ensure that
the airflow volume is equally divided among the
diffusers.
• Fully open the diffuser throttling damper. Add any
necessary throttling damper(s) farther upstream,
nearer to the air terminal unit.
• Replace the diffusers with larger ones or those with a
significantly lower sound rating.
Excessive Room Exhaust Air Sound
This may be due to a sound source located close to the
exhaust grille in a ceiling plenum arrangement, or to the
exhaust system itself. Exhaust system noise is usually
higher pitched sound often caused by a high pressure
drop across the air grille. (Ensure the problem is the grille
by removing it and noting if a substantial reduction in the
sound level occurs.)
• When an exhaust plenum is used above the room
ceiling, determine if the sound is actually due to a
piece of equipment (such as, terminal unit) located
close to the exhaust grille. If so, relocate the exhaust
grille away from the noise source.
• In ducted exhaust systems, ensure the duct
centerline is relatively straight for 1 to 2 duct
diameters immediately prior to the grille assembly
collar.
• Replace the grille assembly with a larger one or
multiple grilles if the problem is due to high airflow
through the grille.
• Lower the static pressure in the exhaust system to
prevent excessive pressure drops.
• Seal the exhaust system to minimize any excess
airflow that is caused by leaks into the system.
Noise Transmission From Another Area
• Use lined ductwork between the noisy area and the
affected areas.
• Locate the duct termination point in the source room
to a location less susceptible to picking up the sound.
(Avoid locations directly above or near sound
producing equipment.)
• If possible, add a lined S curve in the duct connecting
to the noisy area.
• Lower the sound at the source by enclosing the
equipment within a sound absorbing enclosure.
• Reduce the overall sound level in the source room by
using wall and ceiling sound absorption (acoustical)
linings.
Siemens Building Technologies, Inc. 99