Noise characterization and reduction techniques of multiple axial fans unit

Experimental noise characterization is performed on a multiple axial fans unit that is used to force air in common house hold or industrial appliances for cooling purposes. The acoustic field generated by the fans unit is mapped at two different conditions; namely, the normal operating condition and the maximum possible rotational speed. It is found that the noise generated by the fan unit has a distinct whistling tone at a frequency that matches the blade passing frequency. The whistling tone may be amplified due to further fluid-sound interactions with the casing of the unit. Hence, several noise reduction techniques are investigated in order to reduce the noise generated from the fans unit, such as annular silencers and L-shaped silencers. Finally, an innovative compact reflective/absorptive silencer is designed and the measurements indicate that it can achieve a noise reduction of 6.3 dBA at normal operating conditions and 9.5 dBA at extreme operating conditions. © 2017, Canadian Acoustical Association. All rights reserved.