Chapter 31 – Noise

Publisher Summary Many components used in refrigeration systems are major sources of sound and these are often located in occupied buildings and offices. Unwanted sound is noise, and awareness of the potential noise nuisance of equipment is vital, both in the indoor and outdoor environment. All manufacturers publish sound levels for their products and such figures should be scrutinized and compared as part of a purchasing decision. Each compressor type produces a different type of sound, mainly due to its operating principle (reciprocating, centrifugal, and scroll) and it will also depend on its design and manufacturing process. Centrifugal fans produce most of their noise at low frequencies, whereas axial types generate higher frequency noise. Fans with high tip speeds will generate noise levels that may require attenuation. The normal treatment of this problem is to fit a lined section of ductwork lined with an absorptive material on the outlet or on both sides of the fan. Such treatment needs to be selected for the particular application regarding frequency of the generated noise and the degree of attenuation required. Some compressors can be fitted with sound jackets that considerably reduce the airborne sound leaving the source.