The noise of cooling fans used in heavy automotive vehicles

This paper is concerned with the reduction of noise from automotive cooling systems. A comparison is made between the use of axial flow and centrifugal fans and formulae presented for obtaining the octave sound power for each type of fan. The disadvantages of centrifugal fan installations are highlighted and axial fan design configurations are examined with the object of providing optimized systems. Experimental results are presented for different axial fans and comparisons made of the noise measurements with the ingested flow distortions measured by means of a hot wire anemometer. The results indicate the limits of maximum noise reduction which manufacturers may expect using existing fan designs and also indicates the methods for achieving maximum noise reduction for these configurations.