Estimating community noise levels from outdoor condensing units

Abstract

Noise levels propagated from cooling towers and condensing units located in partial or fully enclosed equipment courtyards onto adjoining residential properties were studied in this paper. A combination of field measurements at existing installations, computer model studies of the installations and physical acoustical model studies were conducted to determine the acoustical effects of reflections from enclosing walls of nearby buildings and partial equipment yard enclosures on sound propagation at distances away from the units. Predictions using distance attenuation and the effects of partially enclosing walls (Harris, 1991; Miller, 1981) were used to estimate sound levels at various distances from several existing outdoor condensing units. Acoustical measurements were made at the actual installations within the chiller enclosure and at various distances in the surrounding communities. Each of the actual situations was simulated in model form at a scale of 1:10. The process of calibrating the model to the existing situations will be presented. The scale model data were within 2 dB of the actual insertion losses for full size octave bands from 63 to 2000 Hz for condensing units in the open and in various enclosures.