“Most jobs don’t have acoustical problems, but when you have one, you have one,” Fly said. He himself has a long background in noise reduction the Asbjornson center is the second dedicated acoustic lab of which he has overseen the construction. Some projects use an acoustical engineer along with a mechanical engineer to improve sound quality, Fly said, but this isn’t common. “This is harder to do when the noise and speaker are mixed together and delivered to a single point, be it a headset or a desk speaker.” “When everyone is in the same room and the room is noisy, people naturally compensate and - to some extent - mentally filter out noise, since the noise is usually coming from a different direction,” Osborn said. Some workers will continue to work remotely, making video conferencing still crucial and the ability to hear even more important. They’ve been working in the relative quiet of their homes. Osborn said returning workers may prove more sensitive to usual office space sounds. He said directing airflow only to occupied areas would reduce noise as well. Fly said HVAC equipment is selected to run at peak capacity, but that peak capacity isn’t what it was. The number of people in office building at any time has been much lower in the past year and a half, and no one seems to know for sure what occupancy will be like going forward. But it also makes the system work harder to move air. Sometimes that helps with sound issues, Fly said, because the filter blocks noise. Building operators want more air changes. ![]() The pandemic has created some new challenges for reducing noise. But they also put material in the air that many people were concerned about. Fly said fiberglass liners were once common in ductwork, reducing the noise. “Everything is becoming more electronic, so the advances in variable speed have been quite substantial over the past few years,” Lopes said. Think of a howling wind on an autumn day. Air speed creates turbulence, and that makes noise. This allows the fans to regulate the airflow rather than having to depend on dampers. The other main way to decrease noise, Lopes said, is through the use of variable speed. That area can then be insulated to further dampen the noise and also cut down on thermal losses. By physically separating that, the noise is less likely to pollute the airstream. For example, Lopes said, much of the noise in an air handler comes from the compressor. ![]() Often this means larger, straighter duct runs and larger face areas of filter banks, he said.Īnother solution is isolating the biggest sources of noise. Osborn said one way to reduce fan noise is by reducing the static pressure drops in the system. “Everything in engineering is a trade-off,” Fly said. However, forward-curved fans are less efficient than other options that might create more noise. Forward-curved fans, which were the traditional design for years, made a constant noise but produced a more pleasant tone. David Fly, executive director of Aaon’s Norman Asbjornson Innovation Center, said this is one of the first trade-offs that needs to be considered in designing an HVAC system. Starting at the source, one way to minimize sound is by optimizing the selection of fans.
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