Directional microphone assembly
A directional microphone assembly for a hearing aid, and methods of assembling a directional microphone, are provided. The hearing aid has one or more microphone cartridge(s), and first and second sound passages. Inlets to the sound passages, or the sound passages themselves, are spaced apart such that the shortest distance between them is less than or approximately equal to the length of the microphone cartridge(s). A sound duct and at least one surface of a microphone cartridge may form each sound passage, where the sound duct is mounted with the microphone cartridge. Alternatively, each sound duct may be formed as an integral part of a microphone cartridge.
1. A method of assembling a directional microphone comprising:
providing a directional microphone cartridge with a first sound inlet port and a second sound inlet port;
attaching a first housing portion to the directional microphone cartridge; and
attaching a second housing portion to the directional microphone cartridge, thereby forming a first sound duct that surrounds the first sound inlet port and a second sound duct that surrounds the second sound inlet port, wherein the directional microphone cartridge extends at least partially into the first sound duct and the second sound duct.
2. The method of claim 1 , wherein the first housing portion and the second housing portion are snap-fit together.
3. The method of claim 1 , wherein the first housing portion and the second housing portion are held together using an adhesive material.
4. The method of claim 3 , wherein the first housing portion and the second housing portion are held together using epoxy.
5. The method of claim 1 , further including attaching a plug to an open end of at least one of the first sound duct and the second sound duct.
6. The method of claim 5 , wherein the plug is press fit within the open end.
7. The method of claim 5 , wherein the plug is attached to the open end using an adhesive material.
8. The method of claim 7 , wherein the plug is attached to the open end using epoxy.
9. The method of claim 1 , further including inserting a restrictor into an open end of at least one of the first sound duct and the second sound duct.
10. The method of claim 9 , wherein the restrictor is inserted into the open end in a friction fit manner.
11. The method of claim 9 , wherein the restrictor is inserted into the open end such that the restrictor is flush with a top surface of the directional microphone cartridge.
12. The method of claim 1 , further including inserting a damper into an open end of at least one of the first sound duct and the second sound duct.
13. The method of claim 12 , wherein the damper is inserted into the open end in a friction fit manner.
14. The method of claim 1 , further comprising connecting the directional microphone cartridge to hearing aid circuitry.
15. The method of claim 1 , further comprising connecting the directional microphone cartridge to a hearing aid amplifier.
16. The method of claim 1 , further comprising connecting the directional microphone cartridge to an equalization circuit.
17. The method of claim 16 , wherein the equalization circuit compensates for low frequency roll-off.
18. The method of claim 16 , wherein the equalization circuit provides a flat response similar to that of an omnidirectional hearing aid microphone.
19. The method of claim 1 , wherein the first housing portion forms part of the first and second sound ducts, and wherein the second housing portion forms part of the first and second sound ducts.
20. The method of claim 1 , wherein an overall longest dimension of the assembled directional microphone is less than about 0.215 inches.