NOISE TRANSMISSION FROM A SMALL, HERMETIC, RECIPROCATING, REFRIGERANT COMPRESSOR

Open Access
Author:
Cunsolo, John Vincent
Graduate Program:
Acoustics
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 09, 2018
Committee Members:
  • Timothy A Brungart, Thesis Advisor
  • Stephen A Hambric, Committee Member
  • Daniel Allen Russell, Committee Member
Keywords:
  • Compressor
  • Noise Control
  • Acoustics
  • Refrigerant
  • Transmission
  • Transmissibility
  • Sound Power
  • Sound Power Transfer Function
  • Hermetic
  • Reciprocating
  • Vibration
  • Vibration Isolation
  • Radiation
  • Noise Monitoring
  • Rigid Base
  • Radiation Efficiency
  • Radiated Sound
  • Modal Analysis
  • Mobility
  • Drive Point Mobility
  • Structural Mobility
  • Cylindrical Shells
  • Mode Shapes
  • Structural Loss Factor
  • Spring Surging
Abstract:
In recent years, refrigerant compressor design has become more focused on limiting the emission of noise, as many of these units are installed in residential spaces. This thesis aims to identify the primary transmission path of noise from a small, hermetic, reciprocating compressor to its enclosure, demonstrate the noise issues that result from its structural design, generate a procedure for a facilitated and accurate measurement of radiated sound power using structural acoustics theory, and evaluate a fundamental concept for attenuating mechanical noise. Measurements of transmissibility and radiated sound power of production line and rigidly mounted units reveal that the mechanical transmission path dominates the shell excitation at frequencies critical to human hearing. Experimental modal analysis, shell mobility measurements, and sound power transfer function measurements show that the compressor mounts are located at antinodes of cylindrical shell modes with high radiation efficiency. A noise monitoring technique used to obtain radiated sound power of an operating compressor, given surface-averaged acceleration, is validated with measurements and promoted for use in monitoring structural design changes to products. A noise control concept is designed to decouple the suspension system from its compliant enclosure by grounding it to a rigid base, and it is successfully verified to attenuate the mechanical transmission path. The thesis concludes with possible future design implementations, as well as recommendations on how to reduce radiated noise from similar units.