Experimental Study on the Noise Characteristics Regarding Axial Auxiliary Fans and the Noise Reduction Performance of Mufflers

High-intensity noise not only hurts body and mental health of workers, but also covers sound signs of accidence. To increase the sound absorption and noise reduction performance of axial auxiliary fan noise silencers, the noise strength and frequency distribution of the ambient medium casing of an FBYNo3.0/2.2 (II) axial auxiliary fan were investigated. The noise characteristics at the inlets and outlets were analyzed. Based on this study, a new auxiliary fan bell-type muffler was designed, and its noise elimination ability was tested. The results showed that on the surface of the auxiliary fan casing, the noise intensity exhibited a “V” font distribution in that the maximum noise intensity was located in the air outlet and the minimum noise intensity was located in the middle part of the fan. Mid- and low-frequency noise was presented primarily at the outlets. However, intermediate- and high-frequency noise was presented primarily at the inlets. The muffler performance test revealed that the installation of a muffler can dramatically reduce the intensity of the auxiliary fan’s noise. The mean decrease in noise intensity for various positions was 14 dB (A). The noise elimination rate of the muffler was over 15 %. This decreased level of noise was less than the Chinese national standard for maximum noise intensity, 85 dB (A). In addition, optimizing the noise frequency of the inlets and outlets by decreasing the intermediate- and high-frequency noise of the inlets and the intermediate- and low-frequency noise of the outlets can lead to the greatest noise reduction.