Aerodynamic noise from cooling and HVAC systems features important to land vehicles in urban traffic conditions

The present paper deals with the aerodynamic noise generated by cooling and HVAC systems employed in land vehicles. After a brief description of the physical origin of aerodynamic noise, the features important to system engineers dealing with fans installation and operation are considered. First, the main scaling laws useful to estimate the sound level spectrum are reported. Then, the main characteristics of the sound pressure level spectrum are related to the typical aerodynamic generating mechanisms and to the quality of the perceived sound, and some guidelines for noise reduction are listed. Finally, a method for the employ of results obtainable from laboratory tests is proposed which aims to identify the origin of annoying fluctuations in the received noise.