Noise pollution is a major issue in modern structures. This has a significant impact on the quality of life and productivity of both occupants and neighbors. Mechanical installations such as heating, fans, duct components, air conditioning equipment, pumps, chillers, compressors, stand-by generators, elevators, and escalators are significant noise producers within buildings. If these systems are not properly maintained or installed, they might generate excessive noise, causing discomfort and posing health risks to the inhabitants. Because of rising urbanization and technology, there is a trend to employ local systems installed in ceilings, bringing noise sources ever closer to humans. A plant room’s noise, especially from a huge central plant, may spill outside and irritate nearby residents.
Predictive equipment noise data is readily provided by manufacturers to give a general overview of expected levels. However, this may not be entirely accurate due to difference in installation conditions. Its imperative, to conduct tests once installation is complete and adjust to mitigate the noise levels as per the manufacturer’s recommendations.
Understanding the root causes of noise in buildings is essential for putting into practice efficient solutions to lessen its impact for sustainable development.
This article aims to provide a comprehensive overview of the primary sources of noise in buildings, shedding light on the various factors that contribute to this pervasive issue.
Roof-Top Units
Noise from roof-top units enters buildings through ducts, casing breakout (particularly beneath the unit), and vibration transmission to the roof. Duct noise is treated with absorbent material in the unit or silencers in the duct. Strengthening the unit’s casing or adding sound attenuation materials can control breakout noise. Effective anti-vibration mounts reduce vibration transmission.
Fan Coil Units
These units bring noise sources closer to occupants. Careful selection of low-noise room perimeter units and well-designed inlet and discharge ducts is essential. A discharge silencer or lined duct may be necessary, and noise breakout through the casing should not be ignored.
Fans
Controlling fan noise involves selecting an efficient operating point, designing optimal flow conditions, ensuring vibration isolation from the structure, and using flexible connections to the duct. In cases where fan noise is problematic, in-duct attenuators should be considered.
Variable Air Volume (VAV) Systems
Noise in VAV systems varies based on control methods. Turbulence generated at flow obstructions is the primary source of noise when using dampers or throttle valves. Fan control, whether cycled or modulated, can also introduce noise, and improper air balancing should be avoided. Careful attention to airflow conditions and support is essential to achieve the manufacturer’s specified noise levels.
Cooling Towers
Noise in cooling towers primarily comes from the fan, and details can be obtained from the manufacturer.
Pumps
Pumps generate external noise from the motor, fluid-borne noise from the impeller, and vibration into the structure and pipes. Vibration isolators, flexible connections, and resilient mountings are essential for noise control.
Grilles and Diffusers
Controlling air velocity and flow conditions is essential for reducing noise. Once noise escapes into the room, there’s limited attenuation potential beyond room surface absorption.
Boilers
Noise in boiler rooms stems from the air supply fan and combustion. External noise comes from the flue. The frequency and sound power levels depend on boiler capacity, with low-frequency components in larger units.
Chillers, Compressors, and Condensers
These sources produce tonal and broadband noise. The type and frequency of noise depend on the equipment’s operation mode. Special attention is needed for screw compressors located externally.
Escalators & Lifts
Escalators can produce noise and vibration from the motor and drive mechanism. Correct installation is crucial to prevent issues, but vibration coupling with surrounding structures may require correction if noticeable effects occur. On the other hand lift operations, including door movements and motor surges, can disturb adjacent spaces. Most of the noise is structure-borne, and it can be reduced through design and proper installation.
Stand-By Generators
These generators require testing and often have a separate room for housing. Noise issues arise from air inlet, warm air discharge, engine exhaust, and structure due to vibration transmission. Silencing measures, exhaust silencers, and vibration isolation are necessary.
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