Noise reduction in material-handling machines

Three case studies of industrial noise control relating to two material-handling systems and a press are presented. Each one involves baseline measurements, identification of major noise sources, development and implementation of appropriate design modifications and/or acoustic treatments followed by assessment of their effectiveness. Since the noise from these machines is of an impulsive nature the baseline measurements are carried out with an impulsive SLM. For diagnostic purposes, however, the noise signals were recorded on site and analysed later on a mini-computer. The existing noise level was found to be in the range 100–110 dB(A), major peaks appearing in the 1–3 kHz band. The main sources of noise are the rattling of the components under production in the conveyer systems and their impacts in the various bins. The vibrator units also emit significant noise. The problems were remedied by reducing the drop height and chute slope. Also, a fin system, made of acoustic material, has been designed so that the falling components lose some of their kinetic energy by impacting on the fins. A noise abatement of 10–15 dB(A) was achieved at minimal cost.