This paper presents the results of an investigation of centrifugal blower noise. Experiments on three different types of blowers were conducted to determine the major noise generation mechanisms. The information thus gained has led to an innovative noise reduction method utilizing a stationary, non-contacting transition mesh. Experiments showed that an overall noise reduction of up to 4 dB(A) was achieved for the blowers running at impeller tip speeds of 10 to 30 (m/s). In addition, a semi-analytical model was developed to predict the noise spectra from dimensionally similar blowers. This model yielded an acoustic power proportional to the fourth power of the blower speeds. Comparisons of the calculated and measured noise spectra from different blowers running under various speeds were demonstrated. Good agreements were obtained in all cases.