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Noise pollution has been given more attention due to its negative impacts on human health and disease. The portable low-frequency noise reduction device we developed in this research can provide an effective way for solving low-frequency noise pollution problem in the small space. This work describes the design principle and the prototype structure...
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Noise pollution has become a significant factor, which affects human health living in urban areas. This study aims to explain the relation between noise and different urban land use types such as residential areas, commercial areas, industry areas, green spaces and correlate different samples with the use of urban area and to interpret the results....
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... Also, identification and maintenance of turbine components that could be eroded and produce increased noise are amongst the possible options which could reduce noise exposure risks. Active low-frequency noise reduction using special devices could also be possible, particularly in small, enclosed spaces such as inside the nacelle or small administrative rooms if required (Wang et al., 2016). ...
As the wind farm sector grows and becomes an established renewable energy source, it introduces new materials, technologies and processes that expose workers to increased and unique occupational risks. In this paper, we performed a generic review of scientific and industry literature on online scientific databases and search engines to identify the extent to which occupational health hazards and risks specific to wind farms have been considered. Our review revealed noise, electromagnetic fields, shadow flicker, epoxy and styrene and physical stress have been the focus of limited research, mainly including self-reported data from offshore wind farm employees. Factors such as vibration, welding fumes and other possibly harmful substances, weather conditions and biological hazards have not been addressed by studies, although their presence and combinations could be of concern. Therefore, there is a need for further research on unique and combined risks and hazards faced by workers across all lifecycle stages of wind energy production. This would improve knowledge and provide the opportunity to manage health hazards in current and newly constructed installations and inform future regulatory and other preventative measures.
... This frequency range is considered the most harmful to human hearing, especially when the person is situated at a small distance from the source [24]. For this reason, a number of noise reduction methods were developed, and the methods developed for the frequency of up to 600 Hz demonstrate the greatest efficiency [24][25][26]. The measurement results clearly indicate that the belt conveyor drive system is the main noise source in the low frequency range, i.e. between 200 Hz and 1000 Hz. ...
In compliance with ecological policies, activities undertaken by surface mines in relation to environment protection should be comprehensive and must take into account the principle of sustained development. One of the most basic tasks in this area is to reduce the nuisance caused by the noise emitted to the environment. The problem of above-standard noise levels caused by transportation systems operated in mines can be solved only after major noise sources are identified and analyzed in detail. This article first focuses on the literature studies to describe the possible sources of noise generated by a belt conveyor and in its second part it presents exploratory research into noise sources. The research was performed under laboratory conditions with the use of an acoustic camera as a tool for spatially identifying and classifying individual noise sources. The article identifies some phenomena related to the operation of main belt conveyor components and describes their characteristic frequency ranges.
... In classical topological optimization, the main purpose is concerned with the material distribution that represents the optimal layout in the admissible design domain [1]. The frequency optimization for vibrating structures is avoidance of resonance for the structure subjected to external excitation frequencies within a given interval [2][3][4]. For the optimal design procedure, two main subjects are needed to be treated carefully. ...
... K and M are × the stiffness matrix and mass matrix, respectively. The ℎ eigenfrequency and the corresponding eigenvector can be obtained by solving (3). represents the number of the candidate eigenpairs, and it is suggested to be larger than that prevents the ℎ eigenfrequency exchange its order with the neighbouring eigenfrequency during the optimization process [2]. ...
This paper shows how the reanalysis method can be utilized for speeding up the optimized process in topology optimization related to vibrating structures for simple and multiple eigenfrequencies. The block combined approximation with shifting (BCAS) method is used for reducing the computational effort included in repeated solution of eigenvalue problem, which will dominate a lot of the CPU time, especially for large problems. By utilizing Level 3 Basic Linear Algebra Subprograms (BLAS), the computation efficiency of the BCAS method is improved. For achieving an accurate optimal result, two indicators are presented to control the approximate reanalysis procedure. The effectiveness of the proposed method is demonstrated by three numerical examples.
... There are numerous types of noise around buildings that seriously influence people's living quality [1]. Among these noises, low frequency noise is a major component of many occupational and community noises which is emitted by numerous sources in the society [2][3][4]. The lack of attenuation of low frequency noise by walls, windows, and other structures and its pervasive ambient levels make low frequency noise a factor of critical importance to people's living quality and health. ...
A combined approach based on finite element method, boundary element method, and genetic algorithm (FEM-BEM-GA) is proposed for optimizing the low frequency sound (LFS) insulation performance of plate structures. This approach can identify the optimal structural parameters (especially concerning the effects of arbitrary boundary conditions) so as to maximize the structural overall LFS insulation. The basic ideas of this approach are as follows: (1) the sound transmission loss (TL) analysis of a plate with arbitrary boundary conditions is conducted by the coupled FEM-BEM method; (2) the single-number rating method (such as low frequency sound transmission class) is used to assess the plate’s overall LFS insulation; and (3) the genetic algorithm (GA) is employed for searching the optimal solutions of the multiple-parameter optimization problem. The proposed approach is subsequently illustrated by numerical studies. The results show the effectiveness of consideration of the effects of boundary condition in the plate’s LFS insulation optimization and demonstrate the feasibility and effectiveness of this approach as a structure design tool.
In the active sound control, a domain is protected from externally generated noise via constructing secondary sound sources, which are called controls. These controls are applied on the boundary of the shielded domain. Apart from the external noise, a desired sound generated by interior sources should also be retained inside the shielded domain. However, it turns out it is a challenge to preserve the internally generated sound unaffected due to both the reverse effect of the controls on the input data and sparse distribution on the boundary. To take into account the reverse effect, an innovative algorithm based on nonlocal control is implemented in the time domain for the first time. Its real-time practical implementation may include preliminary tuning to the real surrounding conditions. A number of test cases are considered including external broadband noise and internal monochromatic desired sound. A sensitivity analysis is carried out with respect to some key design parameters such as density of sensors and controls as well as respective geometrical displacement from one another determined by the Hausdorff distance. It is demonstrated that the nonlocal control provides the noise attenuation level, which is not very sensitive to the presence of the desired sound.
Traffic, construction and industry noises are the main sources for noise pollution for mega cities. These noises mainly propagate through the windows of the dwelling and can degrade the comfort level of a living space. Various studies have demonstrated that the active noise control (ANC) system is a potential technique which can be applied on the windows in order to mitigate environmental noise level inside a building. The present paper attempted to give a detailed description for the use of ANC system in windows under various scenarios, namely closed, fully opened and partially opened windows. For closed windows, the most common design methods of ANC system are cavity and panel controls. For opened window, the secondary source is either mounted on the frame of the window or implanted in the walls. For partially opened windows, the most common design method is cavity control. Advantages and shortcomings of various ANC designs were presented and discussed in the present study.
People with hearing disability find it difficult to establish a communication specially because most of the communication mediums that people naturally use are vocal. Hearing impaired people sometimes risk their life in cases like busy roads or run by high speed vehicles. Furthermore, they are unable to hear people calling them. Even if they understand that they are being called or they hear any sudden noise, they can't figure out the direction of the sound which is out of their regular vision. Recent technologies can be used to help them. In this paper we propose a smart glass that will enable them to understand any sudden sound by separating the noise using active noise cancellation and recognize the sound by speech recognition, notify that they are being called and provide them the direction of sound using binaural cue. This glass can also be used for old people or people with lower hearing ability. Which can be integrated with modern commercial smart glasses for better performance and lower price.
