DEVICE FOR DECREASING NOISE IN CAB OF CAB-OVER VEHICLE

摘要

PURPOSE: To provide a device for decreasing the noises in the cab of a cab-over vehicle constituted to more effectively decrease the noises in the cab of the cab-over vehicle by small-sized speakers of a low gain on a bass side. CONSTITUTION: This device is constituted to cut the components below 80Hz among the detected outputs of a vibration detecting sensor 15 by a filter and to drive the speakers 17 by the driving currents subjected to phase inversion by a phase inversion circuit. The noises in the cab are detected by microphones 18 disposed in the side part of the head rest of a driver's seat, the upper part of a pillar, the ceiling right above the driver's seat, etc. The servo control of the phase control circuit in the driving circuits of the speakers 17 is executed according to these detected outputs, by which the phases of the driving currents supplied to the speakers 17 are controlled to optimum values.