Iran Occupational Health

Background and aims: Discharging compressed air through conventional single jet nozzles or open pipes is a common jet noise in industry. This study is aimed to reduce air blow gun jet noise by designing and fabrication of multiple jet nozzle as a substitute for conventional single jet nozzles.
 Methods: One of the most common commercial air blow gun equipped with a conventional single jet nozzles was considered as a reference. An air Nozzle’s three dimensional model with multiple and smaller openings was designed by solid works software and the designed sketch was fabricated by a three dimensional printer. Noise measurement was made by a Cassella Cell 450 sound level meter with one octave band analyzer. Noise absorption foams were applied to mitigate noise reflection in the testing environment. Air thrust was measured using a digital scale that was placed 30 cm away from nozzle tips.
Results: Multiple jet nozzle’s sound pressure level was measured significantly lower than conventional nozzle’s sound pressure level (P Value <0.04). Multiple jet and conventional nozzle’s average sound pressure level in various angles from nozzle axis (30, 90 and 135 degree) was measured to be 75, 76, 76 dB A and 78, 83.3 ,86.3 dB A in pressures of 2,4 and 6 bar respectively. Multiple jet nozzle’s noise reduction in frequencies higher than 500 Hz was significant in comparison with conventional nozzles. Conventional and multiple jet nozzle’s average air thrust in pressures of 2,4 and 6 Bar was measured to be 1.39 and 1.19 N respectively and there was no significant relationship between air thrusts (P Value = 0.7).
Conclusion: Multiple jet nozzle with lower noise and the air thrust that is approximately equal to single jet nozzle, can be considered as an appropriate alternative for noise reduction in air blow guns.