Study on the Active Sound Cancellation Control of Railway Wheel/Rail Noises by On-vehicle-type Devices

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Results of present project are summarized as follows :(1)Sound radiation characteristics of rolling noise and impact noise of railway wheel/rail system were first investigated theoretically by using BEM analysis and besides experimentally by field measurements of actual conventional railway line.(2)The concept of the active sound cancellation control of the railway wheel/rail noises by on-vehicle-type devices was proposed and its possibility was examined theoretically and experimentally. First, by introducing the wave absorbing control principle to cancel the noises radiated from the open under area of the vehicle over the whole lower seeable space, the methods of placement of sensor and actuator in device were constructed, and the validity of its concept in both cases of slab and ballast tracks was verified by the simulation on the basis of the two-dimensional Boundary Element Method.(3)Then, one prototype unit of devices was designed and manufactured in addition to its analog controller. And the laboratory-level experiments were carried out. In the experiments, the floor and side thin plates of a vehicle were simulated by using the Γ-shaped honeycomb panels, and both of a plane-wave speaker and a 60kg rail of length 8m excited by the electro-magnetic shaker were used as the primary noise sources. As a result, it was verified that almost equivalent active control effects of -8dB(A)〜-9dB(A) are obtained at the separated lower two points for the case of the speaker noise source and also for the noise source of randomly excited rail, active control effects of -3dB(A)〜-6dB(A) are actually obtained. Thus, the possibility of proposed concept of active sound cancellation control was fundamentally ascertained. Finally, the future prospect for practical use was examined by BEM simulation and the practical possibility of realization of the presented concept was implied.