Custom HVAC Enclosure for Hoover & Strong
Hoover & Strong, a manufacturer of recycled precious metals had an HVAC noise problem. They had a clean air blower installed in the work area was creating an organizational hazard as noise levels were distracting to employees.
After contacting Technical Sales Representitve, Blake Hall, Acoustical Solutions, Inc. developed a custom fitted sound enclosure to reduce noise levels by 50%.
Application Introduction
Hoover & Strong is a manufacturer of precious metals and have been in business since 1914. 100% off all of their precious metals including gold, platinum, palladium, silver are 100% recycled.
Hoover & Strong utilized a recirculating clean air unit which uses a variable speed blower designed to clean the air that is then ducted within their HVAC system.
Typically these units are installed on roof tops or above ceilings because of the noise levels emitting from the blower.
In Hoover & Strong's case the unit had to be installed within a mechanical room right next to a smelting work area.
Their intention was to offer a better, cleaner work environment but did not want to do so by subjecting their employees to the excessive noise levels being created by the clean air unit.
Treatment Provided
Acoustical Solutions scoped out the job site and saw two problems:
- The unit was suspended from threaded rod, but there was no isolation or vibration hangers separating the unit itself to the ceiling deck above
- The blower on the unit was excessively loud and needed to be enclosed or blocked off from the mechanical room
The Isolation Hangers that we choose to use were the ISOH3B which use both neoprene for stopping high frequency vibrations and a spring mount that work well with the low frequency problems.
The sound blankets that we choose for this application were the ABSC-25 because they are a class 1 fire rated blanket.
Knowing that the blower on the unit is not ideally set within a close proximity to a work area, we needed to add as much sound blocking as we could to the unit, so we choose the ABSC-25-2# version which utilizes a two pound version of mass loaded vinyl sound barrier sandwiched in between two 1" layers of fiberglass then quilted into a vinyl covering.
Installation of the isolation hangers was very straightforward, we simply cut the existing threaded rod breaking the metal to metal connection between the unit and ceiling deck and inserted the isolation and tied the threaded rod off top and bottom on the hanger.
The ABSC-25 sound blankets were a little more challenging. First there were a number of cut outs that would be required for the enclosure and secondly the unit still had to be able to draw in air, but be acoustically sealed on all sides.
The blankets on all 4 sides of the enclosure went on first attaching to fiberglass angle and a concrete header.
The cut outs around pipes etc. were field measured, then cut with a utility knife to the appropriate size being sure not to make to large a cut that would sacrifice the sound quality of the blankets themselves.
Extra edge binding was the wrapped around the cut outs and staples into place to assure that no loose fiberglass was open to the mechanical room.
The second problem of allowing proper airflow to the unit was achieved by making the bottom blanket equipped with a large air flow vent baffle which is essentially an acoustically lined convoluted path that will freely allow to the air to pass but will absorb the sound waves as they try and pass through the ninety degree bend or turn within the vent baffle.
Results & Project Take Away
From this application we can clearly see that not all acoustical problems can be solved with just one product.
In this instance of we just used isolation hangers or just used the sound blankets we would have only treated either the structure borne sound being transferred into the room through the metal to metal connection between the unit and the ceiling deck.
If we only put up the sound blanket enclosure we only would have been treating the air-borne sound transmission from the blower that was causing problems.
After the installation was complete and the unit was turned back on, the on site supervisor from Hoover & Strong commented, "The unit is at least 50% percent quieter than it was before".
For more information on this application, contact Blake Hall.
