To improve the absorption and elimination of the vibration from a vibrator and a diaphragm by substantially suspending a box-shaped electromagnetic case in a floating state by suspending members formed by coil spring rings.

Four supports 8 for suspending an electromagnetic case 10 are standed near four corners of the electromagnetic case 10 on a bottom base plate 7. Each one end 3a (having the shape of hook) of suspending members 3 formed by coil springs (extension spring) is locked in each engagement hole 8a formed on an upper part of the supports 8. On the other hand, the other end 3b of the suspending member 3 is locked in an engagement hole 10a formed on a lower part of the electromagnetic case 10. By applying this structure, the electromagnetic case 10 is substantially suspended in a floating state by the tensile force of the suspending members formed from the coil springs.