The Reduction of Low Frequency Gas Turbine Exhaust Noise: A Case Study

A well reported, industry-wide problem with simple cycle peaking gas turbines installed near residences is excessive low frequency airborne noise, sometimes termed “infrasound.” If the noise level is high enough, it can cause perceptible vibration of windows and frame buildings, and provoke an adverse response from the community. Such a situation recently occurred after construction of a four unit GT 11N1 peaking station. A team of specialists and outside consultants was formed to investigate the problem, and a development program found that a thick absorber could be effective against infrasound. This led to the design of a thick panel absorber which was installed at the rear of a 90 degree turn in the exhaust system. Field testing verified that the low frequency noise from the turbine exhaust was reduced by 5.9 and 6.7 dB in the 31.5 and 63 Hz octave bands respectively, and by 5.5 dB(C) overall.