Objectives
FAN NOISE TRACK
CONTEXT
The noise due to fans remains a big issue as fans are encountered in an extremely wide range of products, from the very small axial fans for cooling CPUs' in computers to the biggest ones in air-condensers of power plants, in the every-day life in domestic appliances (micro-wave, dryer), or for comfort or health purposes with the HVAC and ventilation units, at home or in transportation.
Following the success of the last Fan Noise 2007 conference, the track dedicated to fan noise will be a good opportunity to follow the progress achieved by manufacturers and institutions in the comprehension, prediction and control of the fan acoustic mechanisms. Sound system effects associated with the fan installation in complex systems or equipment as well as the design of low-noise fans will also be of great interest. The presentation of new technologies of active and passive silencers will be welcome in the conference.
TOPICS
Fan noise generation
The two main mechanisms are tonal noise at harmonics of the blade passing frequency and broadband noise due to leading-edge, trailing-edge and tip clearance noisen respectively
Experimental methods for noise source identification
Experimental methods remain very important tools to assess the acoustic levels and to get a better understanding of physical phenomena. Many techniques are available, from sound intensity method to correlation techniques with embedded sensors on the blades
Noise prediction and analysis
The noise prediction is also a key issue: analytical and numerical methods become available
Design of low-noise fans
Fan noise has to be reduced at source. Different means are investigated such as the optimisation of the blade shapes, the adjunction of blade tip device for reducing tip clearance noise, etc.
Fan noise control by passive and active methods:
If fan noise cannot be (enough) reduced, other approaches have to be applied such as passive techniques with silencers (actual cases used on site are always interesting) or active control methods to strongly reduce the sound transmitted to the surrounding.
Fan acoustic system effect
System effect corresponds to a coupling between the circuit and the fan, which usually results in a degradation of the aerodynamic and acoustic performances of the fan. The global optimisation of fan installation is an efficient way to reduce noise of the whole system.
Sound quality applied to fans
Sometimes, the physical sound level radiated by the fans cannot be reduced but the feeling of the user can be improved by modifying some characteristics of the sound, called metrics. The sound quality is of great help for a better understanding of the relationship between the feeling of the user and the acoustic spectrum of the fan or, sometimes, the geometrical characteristics.
