Noise produced by fans
Noise optimized active cooling is becoming increasingly significant. The following information provides details on quiet fans by SEPA EUROPE.
The noise development of a fan and likewise the service life is a magnitude that needs explaining. Standard measurement is carried out in an anechoic chamber. The fan is suspended by rubber ropes and measured at a defined distance to the fan hub (air intake side). The relevant standard is ISO 7779 and defines a distance of 1 m.
Small fans however, develop very little noise so that it is preferable to measure at a distance of 0.1 m and the determined value is thus reduced by 20 dB. The results are suitable for
orientation purposes, however they do not represent the actual noise that is generated when installed in a corresponding application. Important factors, e.g. type of mounting, housing
design, housing material, static pressure, unfavourable flow conditions are disregarded during measurement yet they considerably affect the noise of the fan in the corresponding application. The choice of fan and the correct installation depend on several factors and these should be decided together with our experienced fan specialists.
Measures required to reduce noise depend on the actual application and as far as design is concerned, should already be taken during the development phase. As subsequent changes are usually expensive and less effective, the following points should be observed:
Use adequately dimensioned mounting aids for reducing structure-borne noise, e.g.
collars. The fastening devices for elastic securing LM or SLM are available for fan sizes of 30 mm x 30 mm to 120 mm x 120 mm. They enable the quick installation on mounting plates or housings so that the noise can be reduced by up to 9dB.
- Simple and affordable mounting that reduces noise can be achieved by using cable bushings and not mounting the fixing screws directly on the housing wall:
Choose fans with the largest possible dimensions and the lowest speed that is necessary for cooling. Two fans with the same flow rate can develop up to 12dB less noise than one single fan with a higher speed! Unpleasant, „sharp“ high-frequency sound ranges are
reduced more than low and medium frequencies.
Ensure that you operate the fans in the optimum operating range and the intake and discharge ports in the device are generously dimensioned as outside the operating range (too high pressure) the emitted airborne noise rises sharply.
- The emitted noise also depends on the positioning and the blowing direction. Observe the following illustration:
- Choose sleeve bearing fans with extremely low speed as they develop less structure-borne sound than fans with ball bearings. The MagFix® technology of SEPA EUROPE reliably prevents the disadvantages of the older versions of sleeve bearing fans and can be operated in every installation position. Axial and radial fans by SEPA EUROPE with modern blade shape develop considerably less noise with the same flow rate.