Earcup assembly incorporating mechanical active noise reduction

摘要

An earcup assembly for protecting the ear of the wearer from ambient sound in which a cylinder within a shell adapted to surround the wearer's ear and having a resilient seal engaging the wearer's head around his ear, receives a piston which is held in a fixed position relative to the wearer's head to maintain the volume of the space within the earcup between the piston and the ear seal opening approximately constant when the ear seal flexes under the action of ambient noise impinging on the shell.