Experimental study of the noise emission of personal computer cooling fans

A controlled experimental study of the noise emission of a typical model of computer cooling fan, under different operating conditions, was done. The sound–power levels and directivities of 80-mm-diameter Panaflo computer fans mounted in a test plenum were determined from measurements of sound–pressure level over a hemi-spherical surface above a reflecting plane. The design and testing of the test plenum is discussed. Results of tests performed on one fan unit to gain an understanding of the fan’s noise-radiation characteristics and how they vary with operating conditions are presented. The results show that the noise emission of the Panaflo fan is directly related to the voltage and inversely related to the air-flow rate. It was found that the noise level measured at one particular position corresponds well to the average of those measured at 10 points on the hemisphere. The variability of the noise radiation from these Panaflo fans was determined by testing three other fans; variations of resulting total A-weighted power levels were within 1 dB.