An experimental study was carried out to investigate the principal sources of sound from heavy earth-moving machinery, namely a bulldozer and a front-end loader. Major sound sources were the exhaust and air inlet for the engines and the engine cooling fan on the bulldozer. Sound from the exhaust was an important source at nominal one-third-octave midband frequencies from 25 Hz to 250 Hz; sound from the air inlet was a significant contributor in the range of midband frequencies from 25 Hz to 500 Hz. Cooling fan noise for the bulldozer was important in the frequency range from 315 Hz to 3150 Hz. For the front-end loader, the enclosed cab in which the operator sits provided good noise reduction at frequencies greater than 400 Hz up to 20 kHz. Examination of the spectrum of the sound produced by these and other heavy earth-moving machines can indicate the need for maintenance efforts to restore noise-control capabilities that were originally installed or which should be installed. © 2005 Institute of Noise Control Engineering.

Abstract

2005