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Acoustical engineer sounds off about noise control

By Cindy Atoji Keene

Acoustical engineer Herb Singleton always carries a pair of ear plugs with him – it’s not just to protect his ears, which are an important tool for his job, but also because he understands that noise pollution can cause countless adverse health affects, from high blood pressure to hearing loss.

Solving a noise or vibration problem often requires detective skills to track down the culprit, whether it’s a complaint about trains rumbling by or construction site din. “The primary goal of acoustical engineering is the reduction of unwanted sounds, but it’s often challenging to figure out what’s causing the noise and how to control it,” said Singleton, who says solutions include soundproofing a building, adding mufflers to equipment, or erecting noise berms made of soil, stone or rock on a property.

Q: How does acoustics fall under “engineering?”
A: Acoustics is engineering, but it tends to be a mix of electrical and mechanical engineering, with some physics thrown in. Since it's not a "fundamental" engineering discipline, it's not considered by some to be engineering; for example I'm licensed as a mechanical engineer in Massachusetts because the Mass Board of Licensure doesn't recognize acoustics as a separate discipline. This creates problems since the lay public will often defer to engineers in matters of sound, but many of these engineers don't have acoustics training and get sound concepts completely wrong – for example the misconception that trees and foliage make effective sound barriers.

Q: How do you measure noise levels?
A: Sound level meters can measure noise, whether it’s a person in the field or unattended noise monitors that run automatically for several days. These instruments are brought back to the lab and run through the computer. The trade off is that there’s a lot more data but also interfering sounds such as barking dogs or auto traffic that need to be screened out.

Q: What’s an example of a community noise project you’ve worked on?
A: A neighbor lived next to a Sudbury farm that had a noisy chicken coop. He wanted to document the noise levels to show that it wasn’t just roosters crowing in the morning but chickens who were active all day and night. He was able to successfully stop the farm expansion.

Q: How do you address train noise and vibration issues?
A: We can recommend sound mitigation measures by measuring train noise and seeing if it violates applicable noise limits. For example, if steel wheels are spinning on the tracks, they can create an annoying squeaking noise. This can be caused by wheels that flatten over time or have divets in them, in which case the train needs to be maintained or lubrication added to the track. For future rail projects, computer models use equations to calculate a noise level.

Q: You’ve been in this field for almost two decades. What changes have you seen
A: The biggest change is the availability of low-cost computer hardware that has transformed the practice. Now we can perform measurements today using relatively inexpensive tools that might have cost thousands (or tens of thousands) of dollars even back in the late 90's.

Q: What’s your noise pet peeve?
A: Restaurant noise. Restaurants are often intentionally designed to be loud, which bothers me because as a customer, I hate screaming to hold a simple conversation. As a noise control engineer, I also know these high levels often exceed OSHA guidelines and therefore restaurant workers are likely experiencing hearing damage in addition to their long hours and low wages.

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