Very Low Noise, High Efficiency Muffler Designs for Small UAVs

"The role of small acoustically stealthy UAVs for battlefield operations is identified. The challenges associated with noise reduction for such vehicles is described. Novel approaches to reducing the noise emanating from the engine exhaust using an advancedmuffler are presented. These include custom muffler designs, and matching of the aeroacoustic characteristics of the engine and the muffler for optimum efficiency, while reducing noise. The goal is to develop a lightweight (<100 grams), low volume (<24 cu.in. volume, with a max. feature size of 5 in.), low-cost (<$35 each) muffler that retains high efficiency, while reducing noise by 16 dB in Phase I and an extra 10 dB in Phase II. A detailed Phase I work plan is presented, covering analysis, design, build,testing and design evolution tasks. The commercial market for noise-reduction devices is rapidly expanding due to increasing noise concerns in many communities. Small mufflers can be adapted for use with small gas engines in generators, all classes ofmotor vehicles, gas-powered tools, model vehicles, and ultralights."