Abstract: Systems and devices are disclosed herein for absorbing unwanted target sounds. In one example, an acoustic scatterer for absorbing a target sound includes a housing defining a plurality of channels having an open end and a terminal end. The terminal ends of the plurality of channels are separate from each other and extend along a length of the housing. The acoustic scatterer also includes one or more spacers subdividing the plurality of channels along the length of the housing. In another example, a system for absorbing a target sound includes a plurality of acoustic scatterers, each having a housing that defines a plurality of channels having an open end and a terminal end. The terminal ends of the plurality of channels are separate from each other and extend along a length of the housing. The plurality of acoustic scatterers are stacked on top of each other in a lengthwise direction.

Abstract: A system for isolating sound generated by an aircraft utilizing a helipad may include a plurality of acoustic scatterers being disposed adjacent to at least a portion of a perimeter of the helipad. Each of the plurality of acoustic scatterers include channels having an open end and a terminal end. Additionally, each of the plurality of acoustic scatterers has an acoustic monopole response and an acoustic dipole response with a resonant frequency that is substantially similar to one another.

Abstract: The anode-side separator of the present disclosure is an anode-side separator used in a water electrolyzer, and includes a metal substrate made of titanium or stainless steel, and a conductive oxide film containing indium-tin-oxide (ITO) provided on the surface of the metal substrate.