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Air System Quieting

    In building design and renovation, the air handling system is the one prominent noise source that is always in need of noise and vibration control design. Two general types of noise occur:

  1. Fan generated noise, airborne sound, which is caused by turbulence of the air handling unit (AHU) fan wheel which propels the air.

  2. Vibration excited noise, usually low frequency, which transmits through the building structure to be felt and heard in adjacent and lower occupied spaces.

    Common airborne noise reduction measures include lined ducts and in-line sound attenuators. Design tools include manual and computer spreadsheets or special software packages such as Trane's TAP. We use all of these tools. We also go beyond them - applying first principles to solve difficult situations where space is limited or for very quiet installations such as in auditoriums, or to remedy existing noisy installations. For instance, the acoustic plenum makes maximum use of existing building space while providing maximum low frequency attenuation. This is especially useful where circular duct is favored for long distance air movement.

    Common vibration reduction measures include soft springs or strategic relocation of the rotating mechanical systems. Additional attenuation is often needed for higher frequency "vibration" in the form of motion harmonics and magnetostriction of electromagnetic devices such as power transformers. The design criteria, relating to tactile perception of vibration and the annoyance of very low frequency sound (infra sound) are not well known, but we have developed our own criteria which we have found to be appropriate to office and residential occupancy. This was implemented in the top floor of the Nalco Chemical executive offices building in Naperville, IL decades ago.

Last updated 08-Jun-2012.
Original Web Site by Point & Click Software, Inc.