Noise Transmission from a Small, Hermetic, Reciprocating Compressor

In recent years, refrigerant compressor design has become increasingly focused on limiting noise emissions, as many of these units are installed in residential spaces. This paper aims to identify the primary transmission path of noise from a small, hermetic, reciprocating compressor to its shell enclosure, demonstrate the noise issues that result from its structural design, and validate a procedure for a facilitated and accurate measurement of radiated sound power using structural acoustics theory. Measurements of transmissibility and radiated sound power of production line and rigidly-mounted units suggest that the mechanical transmission path dominates the shell excitation at high frequencies. Experimental modal analysis and shell mobility measurements show that the compressor mounts are located at antinodes of highly active and efficiently radiating cylindrical shell modes. A transfer function is measured in order to obtain the radiated sound power of an operating compressor, given surface-averaged accelerations. The paper concludes with proposed noise control modifications, as well as general design recommendations, to reduce the radiated noise from similar units.