Fig. 6 Time-varying correlation, C (t, a), between inside sound of mess hall and bearing vibration.
Fig. 7 Time-varying correlation, C (t, a), between inside sound of mess hall and bearing vibration.
Therefore, this component correlates strongly with the sounds inside the mess hall. As the reduction gear stops the operation after deceleration, the correlation factor is scarcely observed from the figure.
5. Conclusion
In this paper, by applying such measured signals as vibrations to analyzing wavelets, we obtained time-varying correlations between inside room noises and vibrations. From the application to the noise analysis of a mess hall of training ship, following concrete results are obtained; (1) a time-varying correlation between acoustic and vibration signals is clearly analyzed, (2) the starting point of main engine deceleration can be detected accurately, (3) after deceleration, the correlation between two signals becomes unclear on the time-frequency domain, (4) in a rapid deceleration, the load on the propeller increases suddenly. and then the AW of vibration signal, ψ4,b(t), becomes dominant and (5) this method allows for selection of reference signals to meet the active control. It is also made clear that the results are applicable to the selection of reference signal of ANC effectively.
The relation between the vibration in the mess hall and the vibration in the engine room will be made clear in the future. In addition, we want to determine the best choice of window length of AW and the automatic estimation of t-s analysis.
Fig. 8 Result of ANC using time-varying correlation, C (t. a)
Fig. 9 Time-varying correlation, C (t, a), between inside, sound of mess hall and bearing vibration.
Acknowledgment
We would like to thank the crew of Oshima maru and Mr. N. Hagino for their considerable assistance. In addition, part of this study was made possible by a Mazda Foundation Research Grant.
References
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