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DSC Engineers Provide Improvements to Reduce Noise
Contributions to the Community
Environmental Compliance
When a resident near the Drive Systems Center (DSC) notified Bell of a loud noise coming from the plant, a group of engineers got together to see what they could do about it.
"We had to find out what the complaint was, figure out the problem and see what we could do about it," said Ron Jenkins, Engineering specialist. With the help of Barbara Wilds, DSC Safety & Environmental administrator, the noise source was identified and measured.
As it turned out, the problem wasn't any of the heavy machinery within the center, located on Texas 360 in Grand Prairie. It was a pair of fans that run nonstop to cool an automated test stand for a V-22 oil cooler blower.
"The cooling fans produce a distinctive, high frequency sound that is different from the ambient noise on the highway," said Troy Bunch, Drive Systems Test Laboratory chief. "In this industrial environment over here, we didn't pay much attention to the sound, and the fans were not loud enough to violate any noise codes or regulations."
However, on nights and weekends as the highway gets a little quieter, the high-pitched whine, similar to feedback from a guitar amplifier, became more apparent across the highway in the residential areas. The DSC uses many other fans to cool equipment, several of which are actually louder than the test stand cooling fans. But the larger fans move more slowly and the deep rumble they generate isn't as piercing as the high-frequency units, which are required due to the lab's space constraints.
The fans - one intake, one exhaust - are fairly small, flat-bladed affairs similar to what you might find in your house, but much more powerful and a lot noisier. They're housed in a metal box inside the Drive Systems Test Lab. Large ducts carry cool air into the test stand and blow the hot air out via the roof.
"The noise from those fans also goes back out, just like you were talking in a tube," Bunch said.
Initially, the stand was shut down after first shift each day and on the weekends. That wasn't a feasible permanent fix, however. The test stand is designed to run 24 hours a day.
The solution? Stick a muffler on it - or in this case, about a dozen of them. Bunch and Jenkins designed the system. Principle Test Specialist David Vigen drew up the plans. It was put in place around the first of May. It wasn't quite as easy as it sounds. Designing a system was tricky because it could not restrict the air flow, which car mufflers frequently do. The test stand already runs in excess of 125 degrees on a constant basis. Any hotter, and some test stand electrical components could start to fail.
"The fans still perform as well as they did before," Bunch said. "It's much, much quieter. It works better than our original noise reduction goal." The system is similar to a glasspack muffler on a car, which has a straight pipe with a double wall that's insulated to tone down a specific frequency. Even with the muffler system, the whine can be uncomfortable for anyone standing next to the exhaust and inlet - but it's a great improvement over the unmuffled sound. Now the fans can't be heard beyond the boundaries of the factory.
"With a little bit of work, we were able to design this fairly straightforward system just to be a good neighbor," Bunch said.