Frequency Bands Of Spectrum Research Articles

Noise of Centrifugal Fans

Extensions of earlier studies [J. Acoust. Soc. Am. 26, No. 2(1953)] on ventilation system noise are reported. It is shown here that in properly engineered ventilation systems the over-all sound power level in decibels re 1013a watt is related to the horsepower rating of the fan motor by the formula: PWL = 100+10 1og10hp. The octave frequency band spectrum slopes off with increasing frequency at the rate of 5 decibels per octave. The level in the first band is one decibel below the over-all level. Measured data on fourteen fans in actual installations yield a spread of about ±4 db around these relations.