A BP refinery in the USA had been quoted $1.25 million for silencers for five 1.5MW double entry ID fans that had been the cause of extensive noise complaints. Their acoustic consultant had come across our aerodynamic fan noise control technology on the web and contacted us for advice. He sent his noise data to us by email and we identified that our technology would work well on the fans.
We used the information provided to design the aerodynamic modifications and sent drawings so that the components could be made locally. After installation that required a tiny fraction of the down-time associated with fitting attenuators, the 180Hz blade pass tone had been completely eliminated (>12dB reduction), preventing any further noise complaints.
The total project cost for all the modifications not only saved over $1,000,000 compared with the quotations for conventional silencers, but, in contrast with traditional mufflers, the modifications had no effect on fan efficiency and will last the lifetime of the fan with zero maintenance. No site visits were required, saving time and resources (transatlantic flights etc).