Unger Technologies has been involved with several outdoor HVAC Chiller
noise applications. Air cooled chillers with rotary screw compressors
present the largest challenge because of the multiple sound sources and
the tonal quality of the noise. Below are some actual case histories of
Unger’s involvement with outdoor environmental noise control dealing
with air cooled chillers.
The following is actual excerpts from a City Hall Meeting Regarding
Chiller Noise from a McQuay Air Cooled Screw Chiller
-“He spoke of mitigation analysis measures dealing with localization and
definition of noise source, state and federal noise guidelines, noise
annoyance survey and mitigation procedures. The noise emanates from the
screws.”
-“Peterson wants community involvement. He wants the neighbors to know
something is being done and that they have an idea of what is going on.
He has sent surveys out to 70 households selected by distance from the
chiller.”
-“Peterson showed a structure which contained the chiller which was
nonreflective and all perforated and about 4 inches thick. It is very
modular. It can be two, three or four sided. The weight will not be a
problem but wind sheer is the biggest concern.”
Sound Barrier Wall – two Trane Screw
Chillers
Photo #1 was an application of two Trane air cooled chillers located
outside of a hospital. Disturbing tonal noise was being produced to the
adjacent neighbors 2 blocks away. The chiller produced a distinct tone
measured at 125Hz. A city noise ordinance was in place. Unger performed
field sound measurements with a 1/3rd octave band sound level meter both
near/far field along with property line sound measurements. It was
determined that the chiller was indeed exceeding both day and night time
noise ordinances from the City. Unger Technologies provided an acoustic
noise survey and feasibility report. The conclusion was to design and
construct an outdoor sound barrier wall. Our report concluded and
recommended the appropriate modular sound control panels with design on
height and dimensions of the wall. Sound readings were conducted after
construction when the chiller was fully loaded and sound values were
determined below the city code ordinance.
Sound Barrier Wall – McQuay Chiller
Photo #2 was an application of one McQuay air cooled chiller located
outside of a public recreation center building. Disturbing noise was
being produced to the adjacent neighbors 800’ away at a slight change in
elevation to the chiller location. No noise ordinance was in place at
the city/state level. Unger Technologies was retained by the Architect
and City to perform a noise survey and recommended noise abatement
strategies. Unger took field sound measurements with a 1/3rd octave band
sound level meter both near/far field along with property line sound
measurements. Unger Technologies provided an acoustic noise survey and
feasibility report. The conclusion was to design and construct an
outdoor sound barrier wall with acoustic louvers to improve airflow into
the HVAC chiller. Our report concluded and recommended the appropriate
modular sound control panels and acoustic louvers with design on height
and dimensions of the wall. Sound readings were conducted after
construction. Our noise control results met and exceeded our acoustic
goals for the project.
