Most water-cooled chillers scream at around 500-600 Hz. Very annoying especially if you have the room above. Soundproofing chillers takes a combination of mass and absorptive material.
Engineers working with Christopher Newport University in Virginia contacted Acoustical Solutions. They wanted to see what they could do to reduce chiller noise in a new dorm on campus. The chiller was on the first floor of the building and could be easily heard within students’ living areas.
Acoustical Solutions recommended an ABSC-25 AudioSeal™ Combination Blanket enclosure with a roof. This blanket has an STC-33. The engineer was pleased with this solution because of the acoustical results, cost effectiveness, and ease of access required by operators for maintenance. Because the chiller was water cooled, Acoustical Solutions was able to enclose the chiller completely without having to worry
about air circulation problems. The result was a overall dB reduction of about 20 dBA. A 10 dB reduction is half as loud to the human ear. The sound was effectively and dramatically reduced, and students were able to move into their dorm rooms.
Note: We have also used this type of enclosure around several chillers in the basement of the historic homes at Colonial Williamsburg Foundation. They don’t like chiller noise for the visitors. In case you are wondering, they didn’t use water cooled chillers in colonial times, so they didn’t have to worry about the noise.