| 摘要 |
Even in the case where the volume of a back air chamber is small, sounds with a low frequency (low range) can be captured by equivalently decreasing the acoustic impedance of the back air chamber. A dynamic microphone includes a microphone unit 20 that includes a diaphragm 21 having a voice coil 21a and a magnetic circuit 22 having a magnetic gap; and a microphone case 10 that supports the microphone unit 20 on one end side thereof and has the back air chamber 12a provided on the back surface side of the diaphragm 21 via an acoustic resistance material 26 therein. In this dynamic microphone, an additional microphone unit 40 is provided besides the microphone unit 20; a membrane plate 50 consisting of a piezoelectric element, which deforms curvedly toward the back air chamber 12a side according to an applied voltage, is provided between the acoustic resistance material 26 and the back air chamber 12a; and the membrane plate 50 is driven by the sound signal (voltage signal) delivered from the additional microphone unit 40. Thereby, the acoustic impedance of the back air chamber 12a is decreased equivalently. |
