Fang Ji, Xiongliang Yao and Aman Zhang
The structure‐borne sound generated by power equipment can be isolated effectively through vibration absorber under hull base structures. The practical vibration isolation…
Abstract
Purpose
The structure‐borne sound generated by power equipment can be isolated effectively through vibration absorber under hull base structures. The practical vibration isolation performance is limited due to the weight, size and cost. The dramatic attenuating wave propagation characteristic of hull base without adding weight is essential to the vessel acoustic stealth.
Design/methodology/approach
The characteristics of vibration wave propagated from typical shape base link structures have been investigated according to impedance mismatch and wave conversion in non‐homogeneous structure. The hull base is simplified to three degrees of freedom damped system through the mechanical impedance method. The influence of blocking mass weight, as well as location properties to the base vibration isolation performance have been discussed. Furthermore, the structure‐borne sound design of a typical hull base is carried out.
Findings
The impedance mismatch of the hull base is further increased by the comprehensive use of high transmission loss base link structures, blocking mass as well as damping layer. The effectiveness of structure‐borne sound design is verified through numerical calculation together with underwater model test. The test data show that the noise has been reduced larger than 3 dB.
Originality/value
The paper describes what is believed to be the first application of the high transmission loss base in hull structures based on the literature survey. The method of structure‐borne sound design of a typical hull base can be applied in different types of vessels.
Details
Keywords
Fang Ji, Xiongliang Yao, Aman Zhang and Xi Ye
Laying the acoustic decoupling material on the surface of underwater structures is an effective noise reduction technology. The underwater sound radiation experiment of finite…
Abstract
Purpose
Laying the acoustic decoupling material on the surface of underwater structures is an effective noise reduction technology. The underwater sound radiation experiment of finite stiffened double cylindrical shell with separate‐sound and decoupled tile is carried out with the aim of finding out the most effective laying condition.
Design/methodology/approach
The segmentation power function interpolation method and vertex extreme value envelope continuation method are introduced into basic theory of empirical mode decomposition (EMD). The original measured sound pressure signals are decomposed to intrinsic mode function (IMF) group through EMD, and the high‐frequency components are filtered out. Because the mechanical noise of submarine is mainly at low frequency, the IMFs in low frequency are researched through power spectrum analysis. The noise reduction effects of different separate‐sound and decoupled tile laying conditions are compared.
Findings
The sound pressure signal components' amplitudes, periods and phases are obtained through EMD. The test data show that the double cylindrical shell entirely covered with separate‐sound and decoupled tile is the most effective laying condition in noise reduction.
Originality/value
With reference to the case study, this is believed to be the first application of the EMD in sound radiation time‐frequency characteristics of double cylindrical shell. The evaluation of separate‐sound and decoupled tile laying conditions is of great importance in engineering applications.
Details
Keywords
Xiongliang Peng, Kun Yu, Yezi Kang, Kairui Zhang and Qishu Chen
The purpose of this study was to test the mediating effect of psychological entitlement in the relationship between perceived overqualification (POQ) and workplace ostracism. In…
Abstract
Purpose
The purpose of this study was to test the mediating effect of psychological entitlement in the relationship between perceived overqualification (POQ) and workplace ostracism. In addition, the authors posited that POQ would interact with task interdependence to influence psychological entitlement and indirectly affect workplace ostracism.
Design/methodology/approach
Using data collected in three waves from 450 workers in a state-owned enterprise, the authors tested the proposed moderated mediation model.
Findings
POQ increased workplace ostracism through the mediation of psychological entitlement. Moreover, task interdependence buffered the positive effect of POQ on psychological entitlement.
Practical implications
When recruiting, managers should be careful about hiring employees who are too above the job requirements to lessen employees' POQ and lower its negative impact. In addition, they could reduce the feeling of being ostracized for overqualified employees through increasing task interdependence.
Originality/value
Existing research on antecedents of workplace ostracism had mainly focused on the ostracizers, while largely ignoring the victims. Moreover, of the few studies on the victims of ostracism, most focused on inherent employee characteristics or external environmental factors, while little research attention has been given to employees' subjective perceptions. The present study is among the first to examine whether employees' POQ and individuals' self-perception that their skills, knowledge and abilities exceed the job requirements would lead to being ostracized and if so, how and when.