anechoic chambers and noise control products and systems
a worldwide noise control company
A Worldwide Noise Control Company
Anechoic Chambers & Other Noise Control Products and Systems
Anechoic Chambers and Audiometry Rooms
Anechoic Chambers and Audiometry Rooms anechoic chambers home Anechoic Chambers and Audiometry Rooms
Anechoic Chambers and Audiometry Rooms
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ISO 9001

Designing & Manufacturing Anechoic Chambers for over 50 years

STC Hemi-Anechoic Chamber

STC Hemi-Anechoic Chamber

Hemi-Anechoic Acoustic Test Facility for Large Water Chillers

Sound and Vibration Magazine
Robert Stabley, York International, York, Pennsylvania

In a market driven environment, manufacturers of products strive to provide what their customers want. The availability of choices or options allows customers to select those things that are most important in their particular application or use of the product. In the air conditioning and refridgeration industry, York International customers are interested in such things as: cost, operating efficiency, sound levels, maintenance, service, agency certifications, high tech features, etc. These needs often translate into performance/sound testing of their particular systems prior to acceptance and prior to shipment of the units to the jobsite.

The ability to offer demonstrable proof of compliance along with the desire to extend technical competancy required a global testing resource to be created at York International. They developed a uniquely versatile and comprehensive facility for evaluating large water cooled chillers in the HVAC industry. It is capable of precisely measuring both chiller operational performance and sound over a wide range of capacities and operating conditions. With the unique operation of York Chillers to comercial and military cooling needs, both both domestically and internationally, establishing the esential design criteria for the facility was an important task.

ANSI, ASHRAE, ARI, ISO, and MIL standards were reviewed and there requirements collectively considered. Ultimately, the facility was designed to meet the stringent requirements associated with the acoustic/performance testing of high-shock water chillers for the U.S Navy. The capacities and capabilities were then extended to cover commercial systems up to and exceeding 2500 tons of cooling with performance tests carried out in accordance with ARI Std. 575. Satisfying domestic and foreign customers required that both 60 and 50 Hz electrical power at low and medium voltages be made available.

When considering the type of acoustic environment most suitable for evaluating water cooled chillers, a free field above a reflecting plane, approximated by a hemi anechoic chamber with sound absorptive walls and ceiling, was selected so that occupational noise exposure information (based on sound pressure levels) for military and civilian personnel could easily be determined. Under these circumstances the sound pressure levels immediately adjacent to the chillers are not affected by reflected sound energy.

High performance 'V' ridged Supersoft Perforated panels (30 x 30 in.) were provided by Eckel Industries, Cambridge, MA. These panels were attached to a special framework and secured with removable batten strips. The panels utilize multiple layered sound absorbing materials in conjunction with an air space for an overall depth of treatment of 20 in. This design offers a practical and economical method of providing the interior acoustic treatment for a very large hemi-anechoic test room. The completed inside room volume is more than 41,000 cubic ft (37 ft-8 in. wide by 44 ft long by 25 ft high). The facility was equipped with two 3 ft-4 in. by 7 ft-4 in. personnel doors and a very large set of double acoustically-rated doors 18 ft-8 in. wide by 16 ft-2 in. high. Room performance tests indicate that the room meets ISO requirements for Hemi-anechoic rooms down to 100Hz within the desired working area.
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