Noise reduction of weaving looms

Status:

completed 12/2000

Aims:

Weaving looms generally generate a high noise exposure with sound pressure levels in the order of 100 dB(A). These levels present a high risk to the health of exposed employees, and an increased risk of accident. Occupational deafness frequently results from many years of employment in weaving mills; compensation must be made for this, in the form of pension payments, by the responsible institution for statutory accident insurance and prevention (BG). The noise reductions which have already been achieved on weaving looms by design improvements have generally been reversed by the continual increases in production speeds. As the scope for noise reduction presented by conventional design measures on the machines has now largely been exploited, the study is to examine whether the noise exposure of employees can now be reduced by means of active noise control (antinoise).

Activities/Methods:

The noise emission from a modern weaving loom was analysed in the anechoic room of the BG Institute for Occupational Safety (BIA) with the aid of sound intensity and structure-borne noise measurements. The component sound power levels were also determined for discrete elements of the machine in order to record their proportion of the total emitted sound power. Based upon these results, some components of the weaving loom were encapsulated, and suitable positions identified for installation of the antinoise loudspeakers. Supplementary measurements were performed to optimize the loudspeaker positions, and the number of loudspeakers reduced to eight for reasons of economy. Two prototype weaving looms equipped in this way, each with eight loudspeakers and eight control microphones, were then tested under actual production conditions in a large weaving hall.

Results:

Partial enclosures and the replacement of strongly vibrating steel panelling by punched steel plate yielded reductions in sound level of between 4 and 7 dB(A), depending upon the operating condition. The antinoise system enabled reductions to be achieved in the low-frequency range (below 400 Hz) in the approximately 80 cm wide aisle normally present between the machines (on the operator side). Since the noise emitted by modern weaving looms tends to be in the high-frequency range, however, the technology proved unsuitable for this application. The antinoise technology yielded no significant reductions in the A-weighted sound pressure level. The partial enclosures which were tested successfully will be introduced into series production of the weaving looms studied in conjunction with more minor design improvements. Reductions in the sound level in the order of 5 dB(A) can be expected from these measures.

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