Abstract: There is provided a device for propagating acoustic vibrations through an environment. The device includes a low pressure chamber containing a volume of reduced pressure relative to the environment. A movable wall is formed on the low pressure chamber, said movable wall having an ambient side facing the environment and a low pressure side facing the volume of reduced pressure. The movable wall is sufficiently biased towards the environment and away from the volume of reduced pressure such that the movable wall can freely vibrate back and forth relative to the volume of reduced pressure in response to acoustic vibrations impinging on the ambient side of the movable wall. The device has the acoustical compliance of a device of far larger volume.