For roots blowers commonly used in industry, the noise usually comes from the inlet and outlet of the blower, the mechanical noise generated by the casing, motor and parts of the blower, and the vibration transmitted by the vibration of the equipment. Among them, the aerodynamic noise generated by air inlet and air outlet is the biggest and most common noise in fan equipment, which is mainly manifested as rotating noise and fan vortex noise. In severe cases, the fan noise value can reach 120 dB. Most of them are at 95- 105 decibels.

Second, the fan equipment noise reduction target requirements

Fan equipment is mostly used in factories, and the noise reduction requirement of industrial workshops is that the noise in the workshops should be less than 85 within 8 hours. For the range hood or roof ventilator, according to the use environment area, it is required that the second-class commercial office area is lower than 50 decibels at night and 60 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.

Third, the technical scheme of fan noise control

1. Treatment of mechanical noise of fan: Mechanical noise can be treated by improving lubrication between fan parts, assembly accuracy and replacing new parts.

2. Handling the aerodynamic noise of the fan;

Use muffler of air inlet and outlet: The noise of air inlet and outlet of fan is generally higher than that of other positions by 10 dB, so installing muffler at air inlet and outlet can effectively reduce the aerodynamic noise generated by air inlet and outlet. The type of muffler can be impedance compound muffler, and the noise reduction can reach more than 25 decibels.

Use fan soundproof cover: the soundproof cover adopts composite soundproof board as the main body, and encloses a single fan or all fans to become a fan soundproof cover or soundproof room. This method has a good noise reduction effect on the fan, but the site requirements are high. At the same time, the soundproof room should also adopt soundproof doors and windows, ventilation and cooling system, etc.

Renovation of fan room: the original fan room can be soundproofed, and the fan room can be transformed into a completely soundproofed room, and sound-proof doors and windows, sound-proof walls and sound-proof walls can also be used. To block and shield the noise, which helps to reduce the cost.

Treatment of fan pipeline: Fan pipeline will also produce noise, including internal air impact noise and pipeline vibration noise. Sound-absorbing cotton can be wrapped to isolate air impact noise, and damping sound-insulating felt can also be used to isolate vibration caused by impact.

Equipment shock absorption: The fan will generate certain vibration when working, 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 structure.