Fan noise is generated by the cooling fan, and the speed is proportional to. Fan noise is mainly determined by the fan blade cut air or generated by a fan behind the part of the air turbulence generated by changing the diameter of the blade, quantity, shape or angle, and variable vane fan or improve shape can reduce the fan noise fan cover. Fan noise also account for a large share of the internal combustion engine sound source. Fan noise can be divided into the following two categories:
(1) noise (also called the blade noise)-rotating blade periodically cutting the air, causing the air pressure fluctuations caused, for narrow band noise.
(2) the Vortex noise gas swirl around – fans, this effect of eddy currents due to stickiness and divided into a series of separate small Eddy. These eddy currents and their Division cause disturbance in the air, forming process of compression and sparse, thus generating Vortex noise, broadband noise.
In order to determine the type of fan noise and take the appropriate measures of reducing noise, and evaluation of automobile condenser fan noise inside the vehicle, the impact of outside noise, take a test the following scenarios:
(1) contrast with the original state throughout the inside and outside noise conditions;
(2) the condenser fan noise spectrum analysis;
(3) measuring the different speeds of the fan noise;
(4) the measurement point layout:
Internal noise: measure the driver's ear noise (Driver);
The exterior noise: measurement of vehicle front (Front), to the left (Left), right (Right) noise;
Position: in front of microphones on the vehicle longitudinal axis, left and right on the first axis of the microphone, microphones are parallel to the ground, pointing to the vehicle, 1.2m high off the ground, away from the vehicle outline 0.5M.