Empirical Comparison of the In Situ Methods for Determining Sound Power of Typical Embroidery Machine Located in Industrial Workroom

Abstract

Sound power is considered as an excellent measure for evaluating the efficiency of noise controls as well as for comparing noise sources in workrooms. This parameter can be determined by sound pressure or intensity based methods in real conditions of workrooms. This paper aims empirically to compare these in situ methods in relation to a typical industrial machine located in workroom in terms of accuracy, applicability. Determination of sound power of a typical model of noisy embroidery machine located in enclosed workroom was performed in the interested frequency range of 125 Hz to 4000 Hz. Field measurement of sound power was conducted using the BSWA sound analyzer according to ISO 9614 and ISO 3746, respectively. The results showed SWL spectrum of the source was relatively high with flat noise spectrum. Operation speed was one of the most important features which could influence the noise of embroidery machine. In regard to uncertainty values, the sound power spectra, obtained using the two methods, showed acceptable agreement from the viewpoint of applicability. The higher value for pressure methods can be due to fluctuations in background noise and method limitations. Direct measurement of reverberation time compared with approximate method could improve the accuracy of the pressure method. Hence, pressure method can be employed by occupational health experts as an alternative to intensity method. Due to its direct and more accurate measurements, intensity method is considered to be a more preferred technique in order to describe any noise sources and to evaluate noise controls at sources.