Omnidirectional acoustic sensor
An omnidirectional acoustic sensor is provided. The omnidirectional acoustic sensor includes first, inner resonators connected to an inner circumference of a supporting frame and second, outer resonators connected to an outer circumference of the supporting frame. The first, inner resonators vibrate in a height direction of the supporting frame and the second, outer resonators vibrate in a lateral direction of the supporting frame.
1. An omnidirectional acoustic sensor comprising:
a supporting frame;
a plurality of inner resonators connected to an inner circumference of the supporting frame;
wherein each of the plurality of inner resonators comprises:
a vibration unit having a plate shape, wherein a first end of the vibration unit is fixed to the inner circumference of the supporting frame;
a piezoelectric sensor unit arranged on an upper surface of the vibration unit; and
a mass arranged on the piezoelectric sensor unit above a second end of the vibration unit, opposite the first end; and
a plurality of outer resonators connected to an outer circumference of the supporting frame,
wherein the plurality of inner resonators vibrate in a height direction of the supporting frame, and the plurality of outer resonators vibrate in a lateral direction of the supporting frame, perpendicular to the height direction.
2. The omnidirectional acoustic sensor of claim 1 , wherein the upper surface of the vibration unit is substantially coplanar with an upper surface of the supporting frame.
3. The omnidirectional acoustic sensor of claim 1 , wherein:
the supporting frame has a square frame shape, the inner circumference of the supporting frame comprises a first inner surface and a second inner surface, opposite the first inner surface,
the plurality of inner resonators comprises first inner resonators connected to the first inner surface and second inner resonators connected to the second inner surface;
the vibration unit of each of the first inner resonators extends from the first inner surface toward the second inner surface and the vibration unit of each of the second inner resonators extends from the second inner surface toward the first inner surface, and
the first inner resonators are arranged such that lengths of the first inner resonators sequentially increase in a first direction and the second inner resonators are arranged such that lengths of the second inner resonators sequentially decrease in the first direction.
4. The omnidirectional acoustic sensor of claim 1 , wherein a width of the vibration unit, in the lateral direction of the supporting frame, is greater than a height of the vibration unit, in the height direction of the supporting frame.
5. The omnidirectional acoustic sensor of claim 1 , wherein the inner circumference of the supporting frame is a circle and lengths of the plurality of inner resonators sequentially increase along the inner circumference of the supporting frame in one of a clockwise direction and a counter-clockwise direction.
6. The omnidirectional acoustic sensor of claim 1 , wherein each of the plurality of outer resonators comprises:
a vibration unit having a plate shape, wherein a first end of the vibration unit is fixed to the supporting frame;
a piezoelectric sensor unit arranged on an upper surface of the vibration unit; and
a mass arranged on a side of the vibration unit.
7. The omnidirectional acoustic sensor of claim 6 , wherein the upper surface of the vibration unit is substantially coplanar with the upper surface of the supporting frame.
8. The omnidirectional acoustic sensor of claim 6 , wherein the mass, the vibration unit and the supporting frame are formed as one, unitary body.
9. The omnidirectional acoustic sensor of claim 6 , wherein:
the supporting frame has a square frame shape, the outer circumference of the supporting frame comprises a first pair of opposite outer surfaces and a second pair of opposite outer surfaces,
the plurality of outer resonators comprise first outer resonators connected to the first pair of opposite outer surfaces and second outer resonators connected to the second pair of opposite outer surfaces.
10. The omnidirectional acoustic sensor of claim 9 , wherein the mass of each of the plurality of outer resonators is biased with respect to an axis of the vibration unit of the corresponding outer resonator.
11. The omnidirectional acoustic sensor of claim 9 , wherein
the first outer resonators are arranged such that lengths of the first outer resonators on the first pair of opposite outer surfaces of the supporting member sequentially increase in different directions from each other, and
the second outer resonators are arranged such that lengths of the second outer resonators on the second pair of opposite outer surfaces of the supporting member sequentially increase in different directions from each other.
12. The omnidirectional acoustic sensor of claim 9 , wherein the mass of each of the plurality of outer resonators is exposed when viewed from a direction parallel to the outer surface of the supporting frame from which the corresponding resonator extends.
13. The omnidirectional acoustic sensor of claim 6 , wherein a height of the vibration unit, in the height direction of the supporting frame, is greater than a width of the vibration unit, in the lateral direction of the supporting frame.
14. The omnidirectional acoustic sensor of claim 9 , wherein, in each of the plurality of inner resonators, the piezoelectric sensor unit comprises first piezoelectric layer that generates an electrical signal in response to a displacement of the vibration unit, and in each of the plurality of outer resonators, the piezoelectric sensor unit comprises a second piezoelectric layer that generates an electrical signal in response to a displacement of the vibration unit,
wherein the first piezoelectric layer and the second piezoelectric layer comprise one of AN and ZnO.
15. The omnidirectional acoustic sensor of claim 14 , wherein the first piezoelectric layer comprises a c-axis direction piezoelectric material and the second piezoelectric layer comprises a tilted c-axis direction material.
16. The omnidirectional acoustic sensor of claim 9 , wherein, in each of the plurality of inner resonators, the mass comprises silicon, and in each of the plurality of outer resonators, the mass comprises a metal material.
17. The omnidirectional acoustic sensor of claim 1 , further comprising a protection member surrounding the supporting frame.
18. The omnidirectional acoustic sensor of claim 17 , wherein the protection member comprises inlets for sound to travel toward the plurality of outer resonators and outlets for sound to travel away from the plurality of outer resonators.
19. The omnidirectional acoustic sensor of claim 17 , further comprising a connection member that connects to a lower portion of the protection member and a lower portion of the supporting member.