Case History: Testing of Acoustical Curtain Enclosures per AHRI-585 used with Water Cooled Rotary Screw Chillers

Where refrigeration equipment is used as part of HVAC building comfort systems, radiated noise levels may not be adequately attenuated by mechanical room walls. Without AHRI-585 performance data showing enclosure performance, designers and consultants are left predicting enclosure performance based on ASTM E-90 Transmission Loss testing. The advantage of AHRI-585 data is that it represents performance net of all the flanking paths inherent with an enclosure. Enclosure performance numbers are subtractable values which account for leakage around pipe penetrations, at panel seams, near access doors, through view windows, etc. Data was gathered using a medium tonnage screw chiller mounted in an accredited test cell. The "soft" curtain panels are a septum construction with a mass septum layer between quilted absorber layers. The panel STC rating is 29. Enclosure performance numbers are, as expected, significantly lower than octave band TL ratings, but they represent "real" performance values for more accurate modeling of airborne radiated sound. The enclosure was tested at 25%, 50%, 75% and 100% loads. Testing was done with both an open top configuration and with a full roof option for comparison.