machine shop roof


The Machine Shop is an exclusive event center in downtown Minneapolis ( The building was originally a working industrial facility which provides a unique setting for weddings and other events. Upon renovation of the site to its new purpose there was a requirement for a significant amount of HVAC to be added. The mechanical equipment was located on the roof.  Overlooking the roof were high rise condominiums.

Noise Control Challenge

A Minneapolis based acoustical consulting firm, ESI Engineering did a sound analysis in one of the high rise condominiums and determined that although the Machine Shop was in compliance with State and local noise regulations, low frequency HVAC noise was clearly audible inside the condos and overall noise levels were somewhat loud on the balconies.  The Machine Shop, in a desire to be a “good neighbor” decided to pursue an engineered solution to mitigate the low frequency noise.

Noise Control Solution

OES Inc. designed, furnished and installed Sound Screens on a roof mounted dry cooler and two air handlers that utilize condenser fans. Condenser fans are the mechanism used to cool the refrigerant used to cool our buildings. These type of fans move a high volume of air across radiator coils which remove the heat from the mechanical system. Condenser fans are typically three or four bladed fans which generate a low frequency drone that is often alien to the traditional urban and suburban soundscape.

The solution utilized Sound Seal Absorptive Outdoor Sound Blankets as manufactured by Sound Seal Inc. based in Andover, Mass. ( blanket material is rugged and weather resistant for long term performance. The blankets were integrated into a frame design by OES, Inc. The Sound Shield design concept effectively shields the line of site from the high rise condos to the condenser fans while also absorbing the sound energy as it traveled from the fan across the sound shield. Jessica Barrett, Executive Director of The Machine Shop has this to say about the work completed by OES, Inc.

“Our sound issues with neighboring buildings had created significant stress. Working with O’Neill on this project helped us resolve it in a quick and easy way that got the results we needed. The process was exceptional, from communication to execution. Since installing the blankets we have done additional testing that shows we have removed the noise issue from those condensers completely. Both the Machine Shop and its neighbors were very happy with the assistance from O’Neill.”

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