Acoustic panels decrease reverberation for wastewater plant

Industrial plants are known for being acoustically harsh. High ceilings and highly reflective surfaces create reverberations and amplify the noise and din of heavy machinery. Such inhospitable conditions decrease productivity and create safety hazards, presenting a unique challenge for facility managers.

The Coney Island Wastewater Treatment Plant needed to address that challenge after evaluation of acoustic levels in its facility. The Occupational Safety and Health Administration (OSHA) ran tests throughout the plant and concluded noise levels in the pump room and blower room exceeded safe levels.

Average noise levels registered 92 decibels (dBA) in the pump room and 87 dBA in the blower room. At these levels, communication among plant staff becomes difficult, if not impossible, and prolonged exposure could damage workers’ health.

The materials used to construct the two large rooms contribute to the problem. The walls and floors are concrete, and the ceiling is a metal deck — all highly reflective surfaces. In addition, the rooms house several machines that generate excessive noise. However, their construction and configuration are integral to their functions and could not be changed, so the plant’s operators needed a solution that would work within the existing conditions.

Eckel Noise Control Technologies was invited to assess the facility and devise a treatment to reduce noise and reverberation in the pump and blower rooms. Following its own acoustic analysis and evaluation, the company recommended installing Eckoustic Functional Panels (EFPs) on specific wall and ceiling surfaces to achieve a reverberation goal of 85 dBA or less.

EFPs absorb sound and reduce reverberation, decreasing the risk of harm from exposure to excessive noise and increasing the clarity and intelligibility of speech. The acoustic panels are versatile and durable for industrial applications, and they can be used for new or existing facilities and installed around sprinkler heads, lighting fixtures, and heating and ventilation ducts.

The solution

BEFORE: Prior to installing acoustic panels, the pump room’s concrete walls and other features fostered unsafe noise levels.

The pump room (see photos on the left) is 87 feet wide by 153 feet long and 41 feet high. Four sets of 2,500-horsepower (HP) diesel engine generators drive 600-HP motors, which operate the pumps. Prior to the installation of the EFPs, sound level measurements were taken at eight locations within the room at various distances from the engine generators.

With one set of engine generators and three pumps running, the average noise level measured 92.5 dBA. The installed EFPs brought that down to 82.7 dBA, a reduction of 9.85 dBA. With two sets of engine generators and four pumps running, average noise levels registered even higher. Still, the EFPs brought the average below the 85 dBA safety threshold.

The solution covered about 50 percent of the ceiling (6,602 square feet) and about 10 percent of the walls (2,069 square feet) with EFPs. For the ceiling treatment, three-quarters of the acoustic panels are 30 inches by 10 feet, and the remainder are 30 inches by 8 feet.

AFTER: Noise-reducing panels were installed on the walls and ceiling of the pump room.

On the walls, a mix of acoustic panels was installed that measure 48 inches by 8 feet and 24 inches by 6 feet, all standard EFP sizes.

The solution in the blower room (see photo at the top of this article) achieved results similar to those of the pump room. A mix of panel sizes was also used: 30 inches by 10 feet, 30 inches by 8 feet, 30 inches by 4 feet and 42 inches by 5 feet. In total, 2,651 square feet of EFPs were installed in the room, which measures 53 feet by 120 feet long and 25 feet high. With two blowers running, the average noise level fell more than 5 dBA, from 86.6 to 81.3 dBA.

Conclusion

Based on the results, EFPs fit the Coney Island Wastewater Treatment Plant’s needs for noise reduction. The economical panels reined in the facility’s troublesome and hazardous acoustic conditions, meeting or exceeding OSHA requirements.

In general, EFPs offer a practical method for reducing noise in different settings. They are durable and fire-resistant, and require little or no maintenance. The patented, high-performance acoustic panels are made of a perforated metal (aluminum and galvanized or stainless steel) frame that holds a fibrous insulation material, and their size and finish can be customized to fit and complement any industrial layout and design.

Vince Cavaseno is a technical writer for Eckel Noise Control Technologies. He has a broad background in science, engineering and technology, and worked for related industry publications for more than 30 years. He has a B.S. in chemical engineering from the New York University Polytechnic Institute. Eckel Noise Control Technologies is based in Cambridge, Massachusetts. For more information, contact [email protected] or 617-491-3221.