## 3 Vibro-Acoustic Control  
Vibro-acoustic control plays an important role in enhancing the performance of a structure. Once the information about the vibro-acoustic characteristics of a structure is available, an appropriate technique can be established to control the behavior of the structure for achieving a specific objective. Therefore, the development of proper and effective techniques for the vibro-acoustic control of structures has become an important topic of research. [PERSON] et al. [6] proposed a new parallel viscous damping scheme to study the load-bearing design and vibration reduction of a satellite payload adaptor fitting (PAF). The finite element method was used to determine the vibration characteristics of the PAF. Observing the vibration characteristics information, the appropriate number and coefficient of dampers used to design the parallel damping system for the PAF were determined. The topology and sizing optimization techniques were applied to design, respectively, the configuration of the parallel damping system and the lightweight supports for the PAF. The PAF consisting of the parallel damping system was tested for model verification. The test results show that the proposed damping system was effective at suppressing vibration and maintaining stiffness simultaneously. [PERSON] et al. [7] studied the vibration behavior of landing gears consisting of magnetorheological (MR) dampers. A mathematical model of a landing gear equipped with an MR damper was presented to study the vibration characteristics of the landing gear. A new robust controller based on model reference sliding mode control and adaptive hybrid control was established to improve the efficiency of landing impact energy absorbing with the consideration of aircraft weight, sink speed, ambient temperature, and passive damping coefficient. The performances of the present and skyhook controllers were studied in a series of comparative numerical simulations. Compared to the skyhook controller, the present controller can improve the total energy absorbing efficiency by up to 10% and it also has better adaptability and robustness for different landing scenarios and parametric uncertainties. [PERSON] et al. [8] presented a review of the recent advances in using vibration-induced acoustic wave and vibration-induced streaming flow devices for micromanipulation. In the review, they summarized the fundamental theories of manipulation driven by vibration-induced acoustic waves and streaming flow. The recently proposed representative vibro-acoustic-driven micromanipulation methods were also introduced and their advantages and disadvantages summarized. The prospect and development trend of micromanipulation were presented and discussed. [PERSON] et al. [9] presented a comprehensive review of current acoustic methods and recent advances in the localization of buried pipelines. In the review, investigations were conducted from multiple perspectives including the wave propagation mechanism in buried pipe systems, the principles behind each method along with advantages and limitations, representative acoustic locators in commercial markets, the condition of buried pipes, as well as the selection of preferred methods for locating pipelines based on the applicability of existing localization techniques. In addition, the key features of each method were summarized and suggestions for future work were proposed. They pointed out that acoustic methods for locating underground pipelines were proven to be useful and effective supplements to existing localization techniques. Furthermore, the ability of acoustic methods to locate non-metallic objects might be of particular practical value.