New chillers installed on the roof of a university building were the cause of multiple noise complaints about the whine from the units. The proposals for the conventional acoustic enclosures, barriers and silencers were not only very high cost, but they would also have reduced the efficiency of the units, increasing running costs.
The university approached us for alternative chiller noise control options.
Chiller noise diagnosis and control
Narrow band frequency analysis showed that the cause of the complaints was a toothcomb of tones at the 246Hz compressor frequency and harmonics. This diagnosis proved that if these tones could be reduced, then the complaints would cease.
The conventional approach to chiller noise control is relatively crude in that the measures used do not address the sources of the noise, but simply treat the chiller as a noisy "black box" that has to be screened or enclosed. Our approach is precise: identify the source and use an engineering noise control scalpel to cut out just the problem noise components. This provides dramatically lower-cost solutions that have no effect on chiller efficiency.
In this case, a package of high-efficiency damping and local acoustic insulation was designed. Once installed, the tonal compressor noise was reduced by 10dB - 21dB (as shown here), eliminating further complaints.
