NOISE INSULATING DEVICE

PROBLEM TO BE SOLVED: To provide a noise insulating device which improves an electric apparatus in noise insulating properties and is formed at a low cost. SOLUTION: The noise insulating device is equipped with a noise insulating wall 5 surrounding an electric apparatus such as a transformer, a reactor or the like, a sensor microphone that detects noises produced by the electric apparatus or an acceleration sensor 9 that detects the noises as vibrations and is provided on the external surface of the electric apparatus, a monitor microphone 12 that is provided on the top surface of the noise insulating wall 5 or above it or in its vicinity to detect the noises, a speaker 15 which is provided inside the noise insulating wall 5, and a control device 16 which outputs signals detected by the sensor microphone or the acceleration sensor 9 to the speaker 15 so as to make them opposite in phase to the noises produced by the electric apparatus at the installation site of the monitor microphone 12 and feedbacks and controls the output of the speaker 15 so as to reduce the noises detected by the monitor microphone 12 to an irreducible minimum. COPYRIGHT: (C)2003,JPO