HVAC acoustic problem

[johnnychin]

Usually a good design will consider the loudness of the AHU room. Is there any good range of noise to be reckon? I heard it should be in between 60-75dB. Any approach to tackle the humming sound from AHU room next door?

[chemi-cool]

Humming is coming from vibrations.

The AHU must be standing on springs or special rubber.

The fan motor inside should also be isolated from the frame with rubber.

The fan unit have to be perfectly balanced and all the interior walls insulated with acoustic insulation, minimum thickness of 2".
Connection to the air ducts has to be made of flexible material.

Look for vibrations, thats my opinion.

[Peter_1]

We select grilles for rooms with occupants at 30 to 35 dBA, so a big difference.
Humming sound next door: thick walls and covered at the inside with sound proofing isolation. These are perforated steel plates (hard material) with Rockfon behind it (soft material)
You mostly need a soft and a hard material to absorb different frequencies.
If you want to be sure: call a sound lab and let them take measurements. They then can make suggestions for you right on spot.

[solas]

You should provide more information on the application.

If the space you are referring with the AHU is a plantroom and next door is a cellular office, it would suggest bad design on the architects and building services engineers behals.

Plantroom walls should be constructed from high density materials such as blockwork. This is for a number of reasons, primarily fire safety and noise transmission.

As the previous poster suggested, appoint an acoustic engineer. Alternatively, a class 2 sound meter (€100's worth) would indicate the sound pressure level in the room next door to within +/- 2 dB levels. According to CIBSE, NR (noise rating) levels for general offices should be <35. Should the room next door be part of a factory where sedentary work is undertaken, the NR would be 45. Either way, the only effective way of treating noise generated by the AHU is inspecting the units anti-vibs, bearings etc and constructing a the appropriate partition wall.

Finally, I would recommend checking the fire safety drawings to eatablish if the partition referred to above, meets the specification.

Good luck

[shameem]

Hi

In most of the case AHU sound is created by fan motor and air leak from AHU.Make sure your fan motor is install on the vibration isolator and blower alignment with motor is proper.