Microphone unit

1. A microphone unit that has a bi-directional characteristic, comprising: a housing; a diaphragm which is disposed in the inside of the housing; and an electric circuit portion which processes an electric signal that is generated based on a vibration of the diaphragm; wherein in the housing, a first sound guide space which guides a sound outside the housing to a first surface of the diaphragm via a first sound hole and a second sound guide space which guides a sound outside the housing to a second surface, that is, an opposite surface of the first surface of the diaphragm via a second sound hole are formed; the electric circuit portion is disposed in either one of the first sound guide space and the second sound guide space; and an acoustic resistance portion which adjusts at least one of a frequency characteristic of the first sound guide space and a frequency characteristic of the second sound guide space is formed; wherein the acoustic resistance portion reduces a frequency characteristic difference between the first sound guide space and the second sound guide space, wherein when the acoustic resistance portion adjusts the frequency characteristic of the first sound guide space and the frequency characteristic of the second sound guide space, the acoustic resistance portion shows different functions for the first sound guide portion and the second sound guide portion; wherein the acoustic resistance portion is so formed as to act on a sound in a specific high-frequency band; and wherein the sound in the specific high-frequency band is a sound in a high frequency band of 6 kHz or higher.

2. The microphone unit according to claim 1 , wherein the acoustic resistance portion is formed by mounting an acoustic resistance member on the housing.

3. The microphone unit according to claim 1 , wherein at least one of the first sound hole and the second sound hole includes a plurality of through-holes and doubles as the acoustic resistance portion.

4. The microphone unit according to claim 1 , wherein the acoustic resistance portion is formed by mounting an acoustic resistance member on the housing.

5. The microphone unit according to claim 1 , wherein at least one of the first sound hole and the second sound hole includes a plurality of through-holes and doubles as the acoustic resistance portion.

6. The microphone unit according to claim 2 , wherein the acoustic resistance member is so disposed as to block at least part of a route that extends from the first sound hole to the first surface or at least part of a route that extends from the second sound hole to the second surface.

7. The microphone unit according to claim 2 , wherein the acoustic resistance member is so disposed as to block at least part of a route that extends from the first sound hole to the first surface and at least part of a route that extends from the second sound hole to the second surface.

8. The microphone unit according to claim 4 , wherein the acoustic resistance member is so disposed as to block at least part of a route that extends from the first sound hole to the first surface or at least part of a route that extends from the second sound hole to the second surface.

9. The microphone unit according to claim 4 , wherein the acoustic resistance member is so disposed as to block at least part of a route that extends from the first sound hole to the first surface and at least part of a route that extends from the second sound hole to the second surface.

10. The microphone unit according to claim 7 , wherein the acoustic resistance member includes a first acoustic resistance member and a second acoustic resistance member that are separately mounted on the housing.

11. The microphone unit according to claim 9 , wherein the acoustic resistance member includes a first acoustic resistance member and a second acoustic resistance member that are separately mounted on the housing.