1. Analysis of on-site noise of fans

For roots fans which are common in industry, the noise usually comes from the air inlet and outlet of the fans, the mechanical noise generated by the fan equipment casing, motors and components, and the vibration transmission noise generated by equipment vibration. Among them, the aerodynamic noise generated by the air inlet and outlet is the largest and most common noise in the fan equipment noise, which is mainly manifested as rotating noise and fan vortex noise. In serious cases, the fan noise value can reach 1.21 dB. Most of them are at 95-115 decibels.

2. Target requirements for noise reduction of fan equipment

Most fan equipment is used in factories, and the requirement for noise reduction of fan equipment in industrial factories is that the noise in the factory building is lower than 85 respectively within 8 hours. For the lampblack fan or roof ventilator, according to the use environment area, the second-class commercial office area is required to be lower than 51 decibels at night and 61 decibels during the day, and the first-class residential hospitals and other areas are lower than 45 decibels at night and 55 decibels during the day.

3. Technical scheme of fan noise treatment

1. Mechanical noise treatment of fan: Mechanical noise can be treated by improving the lubrication between fan parts, assembly accuracy, replacing new parts and other measures.

2. Aerodynamic noise treatment of the fan:

Use air inlet and outlet silencers: The noise at the air inlet and outlet of the fan is generally more than 11 decibels higher than that at other positions, so installing silencers at the air inlet and outlet can effectively reduce the aerodynamic noise generated by the air inlet and outlet. The type of silencers can be impedance compound silencers, and the noise suppression volume can reach more than 25 decibels.

using the fan sound-proof cover: the sound-proof cover adopts composite sound-proof board as the main body, enclosing a single fan or all fans, so as to become the fan sound-proof cover or soundproof room. This method has good noise reduction effect for fans, but the site requirements are high. At the same time, soundproof room should also use sound insulation doors and windows, ventilation and cooling systems and so on.

fan room reconstruction: the original fan room can be soundproofed, which can transform the fan room into a complete soundproofed room, and can also use soundproof doors, windows, barriers, soundproof walls, etc. for noise isolation and shielding, which will help reduce the cost.

fan duct treatment: the fan duct will also generate noise, including internal air impact noise and duct vibration noise. Sound-absorbing cotton can be used to wrap it to isolate the air impact noise, and damping sound insulation felt can also be used to isolate the vibration caused by the impact.

equipment shock absorption: some vibration will be generated when the fan works, and the treatment measures include laying floating ground on the fan base or installing shock absorption foundation to reduce the sound transmission of vibrating solid structures.