Noise reduction Reduction AHU room

[Manu68]

Hi Experts,

There is a need to achieve 62db Pressure levels inside an AHU room that handle 150K CFM.

Would sound attenutaor in the return line help or in the supply.
Since the work is warm shell, the ducting and further work outside the AHU is not in scope.
There is a mixing box planned hope that helps.

Please comment from your rich experience.

 

[willard3]

Sound attenuators on the supply and return may help. How they are placed will depend to some extent on the AHU configuration.

Why does it need to be this quiet in a mechanical room?

 

[Manu68]

Thanks Willard for the reply. Client is adamant of the noise. Hence was thinking about providing acoustic packing on the AHU skin, in addition to sound attenuators in return and supply. Believe rockwool fibre around the AHU body would make a difference. No idea on costing...

 

[willard3]

Another fix is to use lead-lined sheetrock on the mechanical room enclosure along with the silencers. Any mass you add to the construction will decrease the noise.

 

[SAK9]

Tricky to guarantee noise levels in an AHU plant room as it is largely low frequency breakout noise from the AHU walls.Acoustic lining of plant room walls and ceilings do help.

 

[Manu68]

I thought about 1 inch thick rockwool acoustic lining all around the AHU shell. This when compared to lining around the room wall would reduce cost.

 

[Manu68]

To Willard,
Will there be a need for lead lined sheetrock, as there is no fear of radiation. Lead could lead to higher weight. And lead being a heavy metal.

 

[willard3]

Noise transmission is proportional to mass. You don't need lead, you could use concrete block.

 

[cdxx139]

An acoustical engineer is your best bet if you need to guarantee the 62 dB. Beware they can sometimes go over the top with expensive suggestions.

knowledge is power

 

[MintJulep]

Noise attenuators generally address noise after it has already been created. You would be well served to try to not make so much noise in the first place. Inlet and outlet connections and duct design will be the most important factors in preventing noise.

Mixing box will not help at all, it will hinder. Physics.

Next will be proper selection of fan size and speed to get the design airflow and pressure without adding dampers, baffles etc. to burn off excess.

Achieving such a low noise in a mechanical room will be a difficult challenge, and really requires design from the beginning to do. I doubt that it will be possible if you are just trying to add band-aids on top of whatever equipment and ducting is already there.