Abstract: A device configured to generate an air flow, the device including: a compressor; an air flow duct arranged to convey a flow of air generated by the compressor; a gas-filled cavity disposed beside the air flow duct; a wall separating the air flow duct and the cavity, the wall including at least one aperture; and an acoustic resistive screen covering and held in tension over the aperture of the wall. The screen is in fluid contact with air in the air flow duct and gas in the cavity and is configured to resist air flow between the duct and the cavity. The resistive screen and the cavity together define a noise-damping resonator.

Abstract: A device configured to generate an air flow, the device including: a compressor; an air flow duct arranged to convey a flow of air generated by the compressor; a gas-filled cavity disposed beside the air flow duct; a wall separating the air flow duct and the cavity, the wall including at least one aperture; and an acoustic resistive screen covering and held in tension over the aperture of the wall. The screen is in fluid contact with air in the air flow duct and gas in the cavity and is configured to resist air flow between the duct and the cavity. The resistive screen and the cavity together define a noise-damping resonator.

Abstract: A method of reducing noise in a device configured to generate an air flow. The device includes an air flow duct arranged to convey a flow of air, a gas-filled cavity disposed beside the air flow duct, and a wall separating the air flow duct and the cavity. The wall includes at least one aperture. The method includes optimising an acoustic property for an acoustic resistive screen that is to be held in tension over the aperture, by: determining geometric properties of the cavity, the aperture and the air flow duct; determining, based on the geometric properties, a noise reduction for the device for each of a series of values for the acoustic property of the screen; and comparing the respective noise reductions for the series of values to determine an optimised value of the series.