Summer Sound Series: Acoustic Solutions for Loud Machinery
I manage an office building, and we have some mechanical equipment on the ground floor next to the building that has caused some noise complaints. Is there a somewhat easy and affordable solution to this?
Exterior acoustics and sound reduction can be a bit of a slippery slope due to the amount of variables involved and the fact that the products must be used outdoors, but there are absolutely ways to fix or address problems such as these.
When a machine is running on the outside of a building, a few things happen. The machine, obviously, creates a sound/noise that travels from the machine toward a potential listener in a relatively straight line. At the same time, the sound coming out of the back (or the building side) of the machine is quickly reflected off of the hard surface that makes up the outer wall of the building. Reducing this reflection can sometimes reduce the problem to an acceptable level, but more often than not, some kind of wall or enclosure will be needed.
As I mentioned above, exterior acoustics can be more involved than sound treatment inside of a building because of the vast number of variables involved. In this instance, the machine is bothering people in the adjacent neighborhood. The machine already has a chain-link fence installed around it to keep the machine secure, which is good, as we’re going to need a structure around the machine to support the product.
The most successful product that I have used over the years is the Exterior Grade Sound Blankets which are a lot like a U.V.-stable fiberglass absorber stitched onto a piece of 1lb-per-square-foot mass-loaded vinyl. Imagine a moving blanket sewn onto a piece of lead and you’ll get the idea. These are custom-made panels that will have rows of grommets used for installing the panels onto the fence, and usually vertical, exterior-grade Velcro® seams to attach one panel to the one next to it. They are custom-made on a per-job basis to fit the fence or structure in question. They are very acoustically effective and will last a number of years — even when they are used in the most extreme types of environments. One thing to consider is that these blankets will essentially act like sails and they may not be the right choice in extremely windy or unsupported types of installations.
As I mentioned earlier, another option is to reduce the sound pressure from the echo off of the building, which can sometimes offer enough performance to get you to where you need to be. This is typically done with the EFT-QFA panels. The sizes and locations for these panels should be considered on a per-job basis so feel free to contact me with the details below and we can discuss it specifically. These panels are simply the absorptive part of the curtain panels mentioned above. Since the building is already a better barrier than the 1lb vinyl, the barrier-part isn’t needed.
A newer product to come to market is the Echo Barrier panel. This is an in-stock, exterior-rated sound panel that has been pre-fabricated to ~6.5′ × 4.5′. They are overlapped when installed panel-to-panel rather than attached to one another with Velcro®. One very nice option with these panels is that they can be rented or leased. This allows the customer or end user to lease them for a period of time, rather than purchasing them permanently. If the acoustical reduction is satisfactory, the lease can be bought out, or the lease can expire and the panels can be returned.
If you are experiencing a situation like this, please feel free to send me an email to begin the discussion. A few photos of the situation are always helpful to assist me in understanding your situation. Many times, the address of the location/building can also be helpful as Google Maps or Google Earth allow me to get a bird’s eye view of the area. If you have any frequency-specific sound data, that is a wealth of information, but even your description of the type of noise can be helpful.