August 2022 Newsletter: Keep on Truckin’

The distribution center industry has seen significant growth over the last few years due in large part to the pandemic and its effect on e-commerce. Many new facilities are being built, often close to residential areas, to fulfill last mile logistics. While it may seem like a good idea to have distribution centers close to the residential areas they serve for quick package delivery, this can result in someone’s backyard sounding like a trucking facility at all hours of the day. Read on to learn more about how sound from these distribution centers can be modeled and mitigated.

Most people have experienced a tractor-trailer truck roar past them on a highway, but fewer have experienced the symphony of sounds associated with a stationary or slow-moving rig at a distribution center. When a truck is in operation at a distribution center, sound is produced from several sources: engine and exhaust noise as it moves throughout the site or idles in the bays, back up beepers, air brake releases, and the whine of hydraulic pumps as trailers are raised and lowered. These sounds can occur at all hours of the day and night, and it’s not the only source of noise at these facilities. To condition the interior of these buildings, mechanical equipment including air handling units, exhaust fans, and heaters are often located on the roof of the distribution centers. All of this sound will propagate to nearby properties.

Distribution centers that are close to residential and commercial properties have the potential to exceed local noise ordinances, which is where we step in. An acoustical model can be built using the site plan and the topography of the surrounding area. The anticipated sound sources – such as trucks in various modes of operation or mechanical units humming on a rooftop – are inserted in the model. The calculations consider source spectrum and directivity, spreading losses due to propagation, air absorption, terrain, and obstacles. Using this model, we can determine how the sound sources affect ambient sound levels in surrounding neighborhoods.

So, what to do if the sound propagation model indicates your distribution site will exceed the local noise ordinance? Visual barriers, such as trees or chain link fences, provide little reduction in sound levels. Barrier walls or earth berms are a common solution to block propagating sound. For a barrier to be effective, it has to break the line of sight between source and receiver, and the receiver must be in the acoustical “shadow” created by the barrier. This is sometimes difficult to achieve given the height of some trucks as well as the elevation of some receivers: an extremely tall barrier would be needed to block the sound of a 12’ tall engine exhaust pipe from a bedroom window 15’ above grade. In cases of unfavorable topography or strict limitations on barrier heights, administrative means to reduce propagated sound may be necessary.

Distribution centers and surrounding communities can co-exist with careful consideration of sound propagation. The next time you have a package delivered, be thankful that all you hear is the ringing of your doorbell!

September 2022 Newsletter: Multifamily Offices
Community College of Philadelphia Career & Advanced Technology Center