DESIGN AND FABRICATION OF AN ENCLOSURE FOR NOISE REDUCTION OF A PORTABLE GENERATOR UNIT

Abstract

In a power-starved economy like ours, we often have to depend on auxiliary standby power systems. The implanted use of the generator sets are a common sight which causes excessive noise pollution. The high level of noise not only affects the hearing system but also has a deleterious effect on digestive, respiratory, endocrinal and cardiovascular systems. This investigation was under taken to design and fabricate an enclosure for a portable genset, so as to satisfy the recently adopted environmental norms by The Ministry of Environments and Forests, Government of India. The portable power genset, which was taken up for investigation and development of its acoustic enclosure, is a Petrol start-Kerosene run, 1400 VA unit. The present method of designing of enclosure was based on a comparison of measured noise data obtained from the bare genset with the existing environmental norms to establish the required attenuation. Then the required noise attenuation was achieved by constructing an acoustic enclosure for the genset, which has two ventilation ducts, a cooling fan and an acoustic door. Cooling requirement of the enclosure was estimated by energy balance calculations and the designed system with the auxiliary fan - and duct system was subsequently tested for satisfactory performance. Anti-vibration isolator (polyurethane foam pads) was also employed to reduce the vibratory excitation of the enclosure body which in turn radiates sound. The average transmission loss due to the enclosure on all sides was found to be 31.5 dB(A). Comparison of measured noise level at 1 meter from the surface of the bare and enclosed and isolated genset resulted in an insertion loss 18.5 dB(A). The results are then compared with the various environmental standards and also from the standpoint of speech communication. For reanalysis a test set up was fabricated to determining the sound transmission characteristics of panels over a particular frequency range. Options have been provided in the reanalysis set-up to set both single panel and double panels and varying source to panel distance, panel thickness, and spacing between two panels.