Georgia - Pacific Tissue Operation
Bellingham - Washington

SSA was hired to control environmental noise from the new gas turbine generator located in the old lumberyard of Georgia Pacific to the residential areas located on the hill to the south of the site. The new gas turbine installation used a Solar Mars 100 Gas Turbine Generator with a maximum of 10MW electrical power output.  Complaints had been made by nearby residents raising the concern that the equipment operation was not within the community noise limits.

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Measurements were made in accordance with Chapter 173-60 Washington Administrative Code “Maximum Environmental Noise Levels”.  A Larson-Davis Model 820 Environmental Noise Monitor was used to take 24-hour measurements while a Larson-Davis Model 2900B real-time spectrum analyzer was used to take frequency-specific measurements that could be used for designing mitigation elements.  In addition, measurements were taken at a residential receiver locations overlooking the GP site  1,700 feet away. 

The generator was initially tested with a 3MW load (30%), as this was the maximum output possible due to the maximum available electrical load.  The purpose of the testing was to investigate the source(s), obtain empirical data, and determine the environmental noise increase at the residential receiver.

At right is a graph showing the sound levels produced by the new generator while operating at 30%, with the ambient noise level of other site equipment shown by the green line.  

The equipment was initially purchased without considering that it would be significantly louder than the current equipment.  As can be seen by the graph, the new generator produced noise levels that were more than 20 decibels higher that the previous noise produced at the site.

Measurements made at the residences should sound levels during the same period between 53 and 57 dB(A).

The gas turbine generator was audible due to the high-frequency whine seen in the above graph at 4000 Hz.   With the elimination of the peak, a significant reduction in the overall noise level would be achieved and, more importantly a big difference in what a the neighbors would hear. The source of this noise was the intake which was able to be fitted with an silencer.  The unit selected was designed with  4” insulation and stainless steel perforated metal cells tuned to the peak at 4000 Hz.  The resulting sound spectrum resembles the ambient contour, and the high pitch whine is no longer noticeable.

Noise Control Engineers