Wideband low-noise implantable microphone assembly

• US 20030125602A1
• Filed: 12/20/2002
• Published: 07/03/2003
• Est. Priority Date: 01/02/2002
• Status: Active Grant

• Current Assignee: Advanced Bionics AG (Sonova Holding AG)
• Original Assignee: Janusz A. Kuzma, Sokolich W. Gary
• Inventors: Kuzma, Janusz A., Sokolich, W. Gary
• Granted Patent: US 6,736,771 B2
• Time in Patent Office: Days
• US Class Current: 600/25
• CPC Class Codes: H04R 2225/67 Implantable hearing aids or parts thereof not covered by H04R25/606
• CPC Class Codes: H04R 2410/00 Microphones
• CPC Class Codes: H04R 25/606 acting directly on the eardrum, the ossicles or the skull, e.g. mastoid, tooth, maxillary or mandibular bone, or mechanically stimulating the cochlea, e.g. at the oval window

Abstract

An implantable microphone assembly for use with a hearing prosthesis, such as a fully implantable cochlear stimulation system, includes a diaphragm mounted to an outside surface of an hermetically sealed case. The mounting is made, in one of various embodiments, by way of an hermetic weld around the diaphragm circumference. A gap is created on the underside of the diaphragm when the diaphragm is lifted with internal pressure. An acoustic channel or groove is formed in the wall of the hermetic case to which the diaphragm is mounted. A first end of the channel or groove opens into the gap at a location that is at or near the center of the underside of the diaphragm. A second end of the channel or groove opens to the interior of the hermetic case at a location that is near the periphery of the diaphragm. An acoustic transducer is placed inside the hermetic case and coupled to the second end of the acoustic channel or groove so as to sense variations in pressure that occur in the gap due to deflections of the diaphragm caused, e.g., by external sound pressure. The interior space inside of the hermetic case directly underneath the diaphragm may be used to house and mount other components, such as a battery. The interior of the hermetic case, which interior includes the gap and acoustic channel, is pressurized in order to lift the diaphragm to form the gap and enable the diaphragm to move in response to external forces, such as forces created by sound impinging the skin above the area where the implantable microphone is implanted.

Claims

1. An implantable microphone assembly comprising:

an hermetically sealed case, the hermetically sealed case having a posterior wall, an anterior wall, and side walls that surround and enclose a pressurized space within the hermetically sealed case;

a diaphragm having a perimeter portion and a central portion, wherein the perimeter portion of the diaphragm is hermetically mounted to the outside of the anterior wall of the hermetically sealed case, and wherein a central gap exists between the central portion of the diaphragm and the anterior wall;

an acoustic channel having a first end that opens into the central gap at a location that is near the center of the diaphragm, and a second end that opens to the pressurized space inside the hermetically sealed case at a location that is near the perimeter of the diaphragm; and

an acoustic transducer mounted to the anterior wall within the pressurized space at the second end of the acoustic channel, the acoustic transducer including means for converting sensed pressure variations to an electrical signal, and wherein deflections of the central portion of the diaphragm create pressure variations in the gap and acoustic channel that are sensed by the acoustic transducer;

whereby the acoustic transducer produces an electrical signal representative of external pressure variations that deflect the diaphragm.

2. The implantable microphone assembly of claim 1 wherein the pressurized space within the hermetically sealed case further includes a battery mounted to the anterior wall below the central gap.

3. The implantable microphone assembly of claim 2 wherein the anterior wall is thicker than the posterior wall.

4. The implantable microphone assembly of claim 3 wherein the pressurized space within the hermetically sealed case further includes speech processing circuitry adapted to receive and respond to the electrical signal produced by the acoustic transducer.

5. The implantable microphone assembly of claim 1 wherein the microphone assembly has a bandwidth of at least 5 KHz.

6. The implantable microphone assembly of claim 1 wherein the microphone assembly does not degrade the signal-to-noise ratio by more than approximately 7 dB at low-to-medium frequencies.

7. The implantable microphone assembly of claim 1 wherein the perimeter portion of the diaphragm is hermetically welded to the outside surface of the anterior wall.

8. The implantable microphone assembly of claim 7 wherein the acoustic transducer in the pressurized space is mounted near the perimeter of the pressurized space adjacent the side wall.

9. The implantable microphone assembly of claim 7 wherein the acoustic channel comprises a radial acoustic channel formed integral with the anterior wall.

10. The implantable microphone assembly of claim 7 wherein the acoustic channel comprises a groove formed within the anterior wall.

11. The implantable microphone assembly of claim 7 wherein the acoustic channel comprises a non-radial channel formed integral with the anterior wall.

12. An implantable microphone assembly for use with an auditory prosthesis comprising:

an hermetically sealed case;

a microphone diaphragm mounted to an outside surface of said case;

wherein said diaphragm is mounted so there is a gap behind the diaphragm which allows the diaphragm to deflect in response to external forces; and

an acoustic transducer mounted within said hermetically sealed case, wherein said acoustic transducer is in fluid communication with the gap behind the diaphragm.

13. The implantable microphone assembly of claim 12 wherein the acoustic transducer is mounted near the perimeter of the hermetically sealed space.

14. The implantable microphone assembly of claim 13 further including:

an hermetic weld around a perimeter of said diaphragm;

a channel integral with a wall of said hermetically sealed case that opens at a point centrally located underneath the diaphragm; and

a sufficient pressure within said hermetically sealed case to lift the diaphragm away from the case and create the gap behind the diaphragm.

15. The implantable microphone assembly of claim 14 wherein the channel comprises a channel that passes radially through the wall of said hermetically sealed case.

16. An implantable microphone assembly for use with an auditory prosthesis comprising:

an hermetically sealed case having an anterior wall, a posterior wall, and a side wall, said walls defining an hermetically-sealed interior volume in which electronic components are housed;

a microphone diaphragm hermetically mounted at its perimeter to an outside surface of said anterior wall;

a pressurized fluid contained within the hermetically-sealed interior volume;

a channel passing through the anterior wall that is in fluid communication with the interior volume of the hermetically sealed case;

the channel having an opening located behind the diaphragm at a location that is at or near the center of the diaphragm, wherein the pressurized fluid lifts the diaphragm away from the anterior wall to form a gap behind the diaphragm, and wherein the presence of the gap allows the diaphragm to deflect in response to external pressure; and

a pressure transducer mounted on the anterior wall within said interior volume at the location where the channel passes into the interior volume, wherein the pressure transducer is adapted to sense variations in pressure occasioned by deflection of the microphone diaphragm, wherein the pressure transducer generates an electrical signal in response to the sensed pressure variations.

17. The implantable microphone assembly of claim 16 wherein the anterior wall has a thickness of approximately 1 mm, and the diaphragm comprises a thin metal foil having a thickness of between about 0.05 mm to 0.25 mm.

18. The implantable microphone assembly of claim 16 wherein the pressurized fluid within the interior volume lifts the center of the diaphragm away from the anterior wall a distance of between about 0.010 mm to 0.200 mm, whereby the gap behind the diaphragm has a height of zero at its perimeter and about 0.010 mm to 0.200 mm at its center.

19. The implantable microphone assembly of claim 18 wherein the channel has a first opening that opens into the gap at a point underneath the diaphragm at or near the center of the diaphragm, and a second opening that opens into the interior volume at a point near the perimeter of the interior volume, and wherein the pressure transducer is mounted to the anterior wall at a location near the perimeter of the interior volume.

20. The implantable microphone assembly of claim 19 wherein the pressurized fluid contained within the interior volume comprises a pressurized gas.

21. A method of making an implantable microphone assembly comprising:

(a) making an anterior wall, a posterior wall, and a side wall that can be joined together to form an hermetically-sealed case;

(b) forming a channel that passes through the anterior wall, the channel having a first opening near the center of an outside surface of the anterior wall, and a second opening hear the perimeter of an inside surface of the anterior wall;

(c) hermetically welding a thin diaphragm at its perimeter to the outside surface of the anterior wall, wherein the diaphragm covers the first opening of the channel at or near the center of the diaphragm;

(d) mounting a pressure transducer to the inside surface of the anterior wall so as to cover the second opening, wherein the pressure transducer includes means for converting sensed pressure to an electrical signal;

(e) mounting and assembling other electronic components to the anterior wall or side all;

(f) hermetically welding the anterior wall and posterior wall to the side wall to form an hermetically-sealed case having an interior volume wherein the pressure transducer and electronic components are housed;

(g) pressurizing the interior volume to a prescribed static pressure, wherein the prescribed static pressure is coupled through the channel to behind the diaphragm and lifts the diaphragm away from the outside surface of the anterior wall to form a gap of 0.200 mm or less between the anterior wall and a center region of diaphragm, wherein deflections exerted against the diaphragm from external pressure cause internal pressure variations in the gap that are coupled through the channel and sensed at the pressure transducer, which pressure variations are manifest in the electrical signal generated by the pressure transducer.