Microphone

1. A microphone comprising:

a microphone unit comprising a first diaphragm vibrating in response to sound waves from a sound source;

an air chamber having a variable volume in response to vibration of the first diaphragm;

a sound pressure detector detecting a sound pressure in the air chamber; and

a volume adjuster, having a second diaphragm forming one side of the air chamber, driven by output signals from the sound pressure detector, changing the volume of the air chamber in response to the output signals from the sound pressure detector, and controlling an acoustic impedance of the air chamber according the change of the volume of the air chamber,

wherein the second diaphragm is vibrated in response to the output signals from the sound pressure detector and changes the volume of the air chamber, and

wherein the sound pressure detector and the volume adjuster configure a feedback control system increasing the volume of the air chamber with an increase in the sound pressure in the air chamber.

2. The microphone according to claim 1 ,

wherein the microphone unit is incorporated into a unit casing, and

wherein the unit casing includes the air chamber having the variable volume in response to vibration of the first diaphragm.

3. The microphone according to claim 2 , wherein the unit casing is incorporated into a microphone casing and the microphone casing includes a power battery compartment.

4. The microphone according to claim 1 , wherein detection signals from the sound pressure detector are input to the volume adjuster through a low-pass filter.