Noise Reduction in Double‐Panel Structures by Cavity and Panel Resonance Control

This paper presents an investigation of the cavity and the panel resonance control in a double‐panel structure. The double‐panel structure, which consists of two panels with air in the gap, is widely adopted in many applications such as aerospace due to its light weight and effective transmission‐loss at high frequency. However, the resonance of the cavity and the poor transmission‐loss at low frequency limit its noise control performance. Applying active control forces on the panels or utilizing loudspeakers in the cavity to reduce the noise prob-lem have been discussed in many papers. In this paper, the resonance of the cavity and the panels are considered simultaneously to increase the noise transmission‐loss. A structur-al‐acoustic coupled model is developed to investigate the vibration of the two panels, the acoustic resonance in the air cavity, and the control performance. The control design can be optimized through the model. Finally, the results will be presented and discussed

Development of dynamic loudspeakers modified as incident pressure sources for noise reduction in a double panel structure

This paper presents a modified loudspeaker source for decentralized feedback cavity control in a double panel structure to reduce the noise transmission. The double panel structure con-sists of two panels with air in between and offers the advantages of low weight, low sound transmission at high frequencies, and thermal insulation. The main issues of the double panel structure are the resonance of the cavity and the high noise transmission at low frequencies. Many papers have discussed applying active structural acoustic control to the panels or active noise control to the cavity. In our previous study, we considered the resonance of the panels and the cavity simultaneously and numerically compared various decentralized structural and cavity feedback control strategies basing on identical control stability margins. Cavity control by loudspeakers, which are modified to operate as incident pressure sources, was found to-provide the largest noise reduction. The incident pressure source loudspeaker can be realized by using a dynamic loudspeaker, a microphone, and a velocity sensor with a feedforward controller. In this paper, experimental results of a one dimensional realization with a feed-forward controller are presented

Comparison of various decentralised structural and cavity feedback control strategies for transmitted noise reduction through a double panel structure

This paper compares various decentralised control strategies, including structural and acoustic actuator-sensor configuration designs, to reduce noise transmission through a double panel structure. The comparison is based on identical control stability indexes. The double panel structure consists of two panels with air in between and offers the advantages of low sound transmission at high frequencies, low heat transmission, and low weight. The double panel structure is widely used, such as in the aerospace and automotive industries. Nevertheless, the resonance of the cavity and the poor sound transmission loss at low frequencies limit the double panel's noise control performance. Applying active structural acoustic control to the panels or active noise control to the cavity has been discussed in many papers. In this paper, the resonances of the panels and the cavity are considered simultaneously to further reduce the transmitted noise through an existing double panel structure. A structural-acoustic coupled model is developed to investigate and compare various structural control and cavity control methods. Numerical analysis and real-time control results show that structural control should be applied to both panels. Three types of cavity control sources are presented and compared. The results indicate that the largest noise reduction is obtained with cavity control by loudspeakers modified to operate as incident pressure sources

Panel Resonance Control and Cavity Control in Double-Panel Structures for Active Noise Reduction

An analytical and experimental investigation of panel resonance control and cavity control in a double-panel structure is presented in this paper. The double-panel structure, which consists of two panels with air in the gap, is widely adopted in many applications such as aerospace due to its low weight and effective transmission-loss at high frequencies. However, the resonance of the cavity and the poor transmission-loss at low frequencies limit its noise control performance. In this paper, the resonance of the cavity and the panels are considered simultaneously to increase the noise transmission-loss. A structural-acoustic coupled model is developed to investigate the vibration of the two panels, the acoustic resonance in the air cavity, and the control performance. The control design can be optimized through the model using a combined stability analysis incorporating both structural and acoustic control. Finally, the results will be presented and discussed

The impact of school bullying on mental health in young adulthood

Purpose: The aim of this paper was to explore the impact of childhood school bullying on subsequent mental health from the perspective of young adults with mental health problems. Background: Quantitative studies have highlighted the negative impact of school bullying on subsequent mental health during adulthood in both cross-sectional and longitudinal studies, however these studies are unable to explain how the perception of and coping response to being bullied in school during childhood may influence subsequent mental health. A qualitative study allows for greater understanding of cognitive and emotional responses to victimisation. Methods: Semi-structured interviews were conducted with 10 young adults with affective disorders and interview data were transcribed and analysed using Interpretative Phenomenological Analysis. Findings & Conclusions: Four superordinate themes were derived: (1) Feelings of exclusion affecting trust in others; (2) I am no good; (3) Troubled by overwhelming torment and unfairness; (4) Not within my control, suggesting the possible roles of maladaptive cognitions, negative internal models, poor coping ability and helplessness in the development of poor mental health. These findings have implications for the use of cognitive or attachment based interventions for victims of bullying

The Trapping and Characterization of a Single Hydrogen Molecule in a Continuously Tunable Nanocavity

Using inelastic electron tunneling spectroscopy with the scanning tunneling microscope (STM-IETS) and density functional theory calculations (DFT), we investigated properties of a single H2 molecule trapped in nanocavities with controlled shape and separation between the STM tip and the Au (110) surface. The STM tip not only serves for the purpose of characterization, but also is directly involved in modification of chemical environment of molecule. The bond length of H2 expands in the atop cavity, with a tendency of dissociation when the gap closes, whereas it remains unchanged in the trough cavity. The availability of two substantially different cavities in the same setup allows understanding of H2 adsorption on noble metal surfaces and sets a path for manipulating a single chemical bond by design.Comment: 11 pages, 4 figure

Comparisons between various cavity and panel noise reduction control in double-panel structures

This paper presents comparisons between various panel and cavity resonance control methods to reduce the transmitted sound in a double-panel structure. The double-panel, which consists of two panels with air in the gap, has the advantages of low weight and effective transmission-loss at high frequency. Therefore, it is widely applied in many areas such as aerospace. Nevertheless, the resonance of the cavity and the poor transmission-loss at low frequency limit its noise control performance. Applying active control forces on the panels or utilizing loudspeakers in the cavity to reduce the noise problem have been discussed in many papers. In this paper, an acoustic-structure coupled model is used to investigate and to compare the transmitted sound reduction of various cavity and panel resonance control methods. The control performance comparison is based on the same stability control margins. Moreover, an adaptive control method is used in the system to further improve the control performance. Piezoelectric actuators on the radiating panel in the adaptive feedforward control combines with the loudspeakers with pressure source in the feedback control is found to be the most effective combination