Sound is an ever present by-product of air conditioning and refrigeration, but is not always a problem. However, in this age of increasing regulation by government agencies at all levels and a greater awareness of noise by the ultimate consumer, the noise generated by systems and their components should be a concern of the designer.

This paper will deal with the problem of noise from positive displacement compressors. The problem will be defined in terms of the typical sound, pressure pulsation and vibration spectra generated by compressors. Data for split systems and rooftop units are presented to show the effect of the compressor on the noise generated by these systems.

In terms of the compressor, the sources of sound, gas pulsation and vibration will be discussed in light of those features of the design which cause and shape the spectra and determine their amplitude. Finally, common methods to attenuate or otherwise reduce the sound, gas pulsation and vibration of compressors will be outlined.