This technology exploits the capabilities of additive manufacturing to attenuate the fan noise within the inlet or aft duct of a turbofan engine. The approach may be expanded to include auxiliary power units, environmental control systems, or other cooling systems requiring noise attenuation.
The acoustic liner consists of multiple paths to provide passive destructive interference. The passages apply an out-of-phase sound field to incoming sound waves, destructively canceling the energy, creating a reduction in overall sound level in the duct. Additive manufacturing techniques may be used to manufacture the complex pattern of passages that is not feasible using current manufacturing techniques.
The liner is conceptually constructed from cubicle building blocks of a straight-through passage and a right-angle passage. These blocks can be stacked and nested to produce passages of various lengths from two block widths to an indefinite number. These configurations can then be arranged axially and circumferentially to produce a complete liner design. The liner can be made from any metallic or non-metallic material suitable for additive manufacturing.