Functional (Unit) Sound Absorbing Panels
Reduce Noice Levels in Waste Water Treatment Facility

Abstract

The topic of this paper will deal with the utilization of unit sound absorbing panels “Functional Absorbers” to reduce background noise and reverberation in the engine generator pump room and the blower room at newly constructed waste water treatment facilities in New York

Noise levels in the pump room and blower room exceed OSHA requirements and communication between workers was extremely difficult. Part of the problem was the nature of the construction of the two large rooms. Walls and floors were concrete and the ceiling was metal deck, all of which are highly reflective surfaces. There were multiple pieces of equipment in each room. Average background noise levels in the pump room were 92 dBA and in the blower room were 87 dBA. A goal was set to reduce the level to 85 dBA or less.

Introduction

In October 1995, rooms within the integrated wastewater and sludge treatment facility were evaluated as to their noise problems. Based on these studies, several rooms would need to be treated with Unit Sound Absorbing Panels.

Acoustical treatment to achieve maximum noise reduction was calculated. Functional (unit) Sound Absorbing Panels were installed on the ceilings and walls of both rooms. Average noise level in the pump room was reduced to 85 dBA and in this blower room to 82 dBA bringing the rooms into OSHA compliance, and reducing reverberation to levels that did not interfere with communication between workers.

Engine Generator Pump Room

In the generator rooms – a room, which is 87 ft. wide x 153 ft. long x 41 ft. high – for example, there are four sets of 2500HP diesel engine generators, with multiple pumps available. They drive 600HP motors, which operate the pumps. With the normal running mode being one engine set is used to drive two or three pumps. The typical overload is two engine sets to drive four pumps. One of the other sets of engine generators is redundant, the other is reserve. Prior to installation of unit sound absorbing panels, Eckel’s Eckoustic Functional Panel, EFP’s. Sound level measurements were taken at eight locations within the room at various distances from the engine generators, Fig.1. Acoustic treatment here involved a ceiling treatment with 6,602 sq. ft. (50%) coverage and wall treatment with 2,069 sq. ft. (10%) coverage. Fig. 2. For the ceiling treatment, three-quarters of the panels were 30” x 10 ft. EFPs; the reminder, 30” x 8 ft. On the walls, the panel sizes were 48” x 8 ft. and 24” x 6 ft. (All of these sizes are standard sizes.) With one engine set and three pumps running the background noise was reduced from 92.5dBA to 82.7dBA after EFP treatment, a reduction of 9.85dBA. With two sets of engine generators and four pumps running, average noise levels were reduced by 6.98dBA, to bring the overall noise level below 85dBA, Fig. 3.

Fig. 1 Before Fig. 2 After

 

 

 

 

 

Coney Island Water Pollution Control Project Noise Survey
Engine Generator Room No. 2-02
One Engine & 3 Pumps Running Two Engines & 4 Pumps Running
Position Before

dBA
After

dBA
Before

dBA
After

dBA
EG1 92.60 82.70 EG1A 93.00 85.80
EG2 93.10 83.30 EG2A 92.50 86.90
EG3 95.60 88.10 EG3A 94.60 88.10
EG4 90.70 80.70 EG4A 91.00 83.40
EG5 92.00 81.60 EG5A 90.10 82.70
EG6 91.10 80.90 EG6A 89.50 82.20
EG7 92.90 82.60 EG7A 93.00 86.00
EG8 92.60 81.90 Change EG8A 91.90 84.70 Change
Average 92.58 82.73 -9.85 91.95 84.98 -6.98
Fig. 3 Noise Survey

 

 

 

Blower Room

Similar results were obtained for the blower room. Here too a mix of panels sizes were used – 30” x 10 ft., 30” x 8 ft., 30” x 4 ft., and 42” x 5 ft. – as the most efficient means of achieving the desired noise reduction. This room measures 53 ft. x 120 ft. x 25 ft.; 2,651 sq. ft. of panels was adequate for effective treatment, Fig.4 & Fig. 5.With two blowers running, the average levels noise reduction with EFPs installed was over 5dBA, from 86.6dBA to 81.3dBA, Fig. 6.

 

Fig. 4 Fig. 5

Coney Island Water Pollution Control Project Noise Survey
Blower Room No. 3-02

Two Blowers Running
Position Before

dBA
After

dBA
BR1 85.50 81.10
BR2 84.90 79.50
BR3 88.60 84.60
BR4 87.80 86.00 (Near Field Condition)
BR5 89.00 82.10
BR6 85.60 81.00
BR7 86.30 79.70 -4.81 Change
Average 86.61 82.00 -5.32 Change W/O BR4
Fig. 6 Noise Survey

Typical Installation Details

Conclusion

Unit Sound Absorbing Panels offer several advantages, as a method of adding sound absorption to spaces with hard reflective surfaces. They can be installed in new or existing facilities without interference with utilities such as sprinklers, lighting, ventilation etc. They require little or no maintenance and are extremely effective in lowering background noise and reverberation in a wide variety of industrial and architectural applications.