Patent ID: 7319771

Claim:
A vibrator for bone conduction type hearing aid devices, comprising: a coil for generating a dynamic magnetic field; permanent magnet means for generating a static magnetic field in a magnetic circuit, wherein the permanent magnet means comprises two permanent magnets that work independently from each other in the magnetic circuit and are arranged such that the static and dynamic magnetic fields are substantially separated from each other, whereby the static field passes through only a part of the magnetic circuit and whereby the vibrator provides an axial force; a casing enclosing the coil and magnet arrangement, wherein the casing forms a part of the magnetic circuit and protects the vibrator and reduces magnetic leakage, wherein the static and dynamic magnetic fields coincide in the air gaps formed between the coil and magnet arrangement and the casing; and inner spring means arranged between the coil and magnet means and the casing so that the coil and magnet means in its rest position is centered in the casing between two air gaps of the same size.