A microphone 1 includes a circuit board 22 equipped with electronic circuits, a microphone unit 26, and a case 21 accommodating the circuit board 22 and the microphone unit 26. The case 21 is a resilient hollow cylinder. The circuit board 22 has a substantially rectangular shape and has shorter sides having a length substantially equal to the inner diameter of the case 21. The circuit board 22 includes contact adapters 222 in contact with the inner wall of the case 21, along the longer sides of the circuit board 22.