Assessment of the mental fatigue state of an operator influenced by electromagnetic noise radiation

Objectives. The problem of determining the mental fatigue of the operator, which is processing the confidential information under the influence of electromagnetic noise radiation, is solved. The relevance of the problem is associated with the need to process the confidential information by the operator located in the limited space of a mobile technical system.Methods. The methods of spectral analysis theory of the results, received in the process of experimental studies the electroencephalograms, are used.Results. The results of experimental studies were obtained based on the processing and analysis of electroencephalograms recorded in standard leads Fp1, Fp2, F3, F4, C3, C4, P3, P4, O1, O2, F7, F8, T3, T4, T5, T6. The following quantitative parameters have been analyzed: power spectral density of delta-, theta-, alpha-, beta-, gamma-rhythms under the influence of electromagnetic noise radiation.Conclusion. The presence of mental fatigue of the operator is based on a comparative analysis of the obtained results and the data described in the scientific literature related to the occurrence of chronic mental fatigue; the fatigue caused by the military performing simulation tasks; mental fatigue caused by performing an RVP test.

Test and Research on Noise Distribution Characteristics of 220kV Oil-immersed Transformer

Large power transformer is the main noise source of substation. With the increase of voltage grade and rated capacity, the noise radiation value of power equipment continues to increase, which has a great influence on the noise standard of substation boundary. In this paper, two test conditions of no-load voltage and load current are considered. The transformer noise testing datum is constructed. The distribution law of factory noise SPL of 220kV oil-immersed transformer is obtained. The test results provide accurate test data for transformer factory noise evaluation.

Composing the noise space: Musical architecture of urban culture

In the recent climate change era of several tropical urban living and cultures, many slums are built on the railroad tracks accompanying the overheating environment. The people in that area can receive the noise radiation that was made from the railroad and the train wheels friction. The design research aims to manage noise with high intensity into the white noise, which was fit and valuable to increasing human life performance in daily life. It enhances through designing the attractive area at Malang urban area as the site and analyzing the environmental psychology approach according to adaptable barriers. This study uses audio editing and music notation software, Adobe Audition and Cubase, to capture the sound to support the design. The results highlighted that musical architecture could bridge the needs of the various people’s living space and noise that cannot be moved and deleted. The play of materials, order, and composition of time that pay attention to the intensity and frequency of noise design project compose the rhythm of formal and spatial settlement design.

Innovative Acoustic Treatments of Nacelle Intakes Based on Optimised Metamaterials

Modern turbofans with high bypass ratios, low blade passage frequencies and short nacelles require continuous development of acoustic linings to achieve the noise reductions expected by the international aviation authorities. Metamaterials and metafluids have been recently proposed as promising technologies for designing innovative acoustic treatments dedicated to reducing aeronautic turbofan noise emissions. In this work, a phase-gradient metasurface treatment is investigated as a way to tackle the noise radiation from an axially symmetric nacelle. This paper aims to study the potential benefits of the mentioned technology, and is not an attempt to design a complete new liner or nacelle. The metasurface is modelled through an equivalent metafluid, and a simulation-based optimisation is used in defining the design parameters. The tonal contribution of the blade passage frequency is considered, and the numerical results with the metafluid optimised on one azimuthal mode at a time show a significant effect in terms of acoustic levels and directivity over an arc of virtual receivers.

Wake-body interaction Noise Simulations by Coupling CFD and BEM

In many engineering applications, the wake-body interaction or body-vortex interaction (BVI) occurs. In the wake-body interaction, vortices shed from an upstream obstacle interact with downstream obstacle and generate noise, for example blades in a turbomachinery, tubes in a heat exchanger, rotating blades like a helicopter and wind turbine and so on. The rod-airfoil and airfoil-airfoil configurations are typical models for the wake-body interaction. A rod and an airfoil are immersed upstream of the airfoil. In this paper, we reviewed the noise mechanism generated by the wake-body interaction and show the numerical results obtained by the coupling method using commercial CFD and acoustic BEM codes. The results shows that depending on the spacing between the rod or airfoil and the airfoil, the flow patterns and noise radiation vary. With small spacing, the vortex shedding from the upstream obstacle is suppressed and it results in the suppression of the sound generation. With large spacing, the shear layer or the vortices shed from the upstream obstacle impinge on the downstream obstacle and it results in the large sound generation. The dominant peak frequency of the generated sound varies with increasing of the spacing between the two obstacles.

Influence of Acoustic Black Hole Array Embedded in a Plate on Its Energy Propagation and Sound Radiation

The plate embedded with acoustic black hole (ABH) indentations is potential for structural vibration and noise control. This work focuses on the mid- and low-frequency performance of plates embedded with the array of ABH for energy focalization and vibration & noise suppression. Plates embedded with two-dimensional ABHs are modelled with detailed Finite Element (FE) models, and the power flow method is introduced to analyze the energy propagation characteristics arising from ABH effect. Then the distribution of average vibration power density along ABH radius is studied. Next, the energy dissipation effects of the plate model embedded with ABH array with two types of damping layers are investigated. Finally, the sound pressure levels of the ABH structure are calculated and discussed. This work is helpful to understand the characteristics of plates embedded with ABH array in reducing vibration and noise radiation. Results show the tremendous potential of ABH array for vibration and noise control.

A Combined CFD-FEM Approach to Predict Fluid-Borne Vibrations and Noise Radiation of a Rotary Vane Pump

The rising demand for lower noise emissions of car ancillary units due to electrification and higher customer expectations regarding driving comfort results in the need for more silent car components. Hydraulic driven car components in particular are often identified as a major source of noise in the system. Therefore, it is mandatory to investigate the noise sources inside the hydraulic system. In this work, a combined CFD-FEM approach is applied to estimate the flow-induced noise radiation of a mechanically driven transmission pump. To achieve this goal, the mapping procedure to hand over the pressure field from the CFD to the FEM mesh must be valid. For this purpose, the error during the mapping process is evaluated and different parameters, which influence the mapping results, are analyzed. Additionally, the impact of the time step size and the length of the time signal on the frequency resolution of the force signal is investigated to get an appropriate excitation force for the vibroacoustic simulation. Subsequently, a force analysis and a structural FEM simulation are performed to identify which flow phenomenon contributes most to the excitation of the pump housing. Specific locations in the pump with high loads are pointed out. In a final step, the results of the vibroacoustic model are compared to acceleration and sound pressure level measurements of the pump performed in a hemi-anechoic room.

Modelling noise radiation from concrete box girder bridges as an infinitely long periodic structure excited by a high-speed train

Concrete box girder bridges occupy over 80% of the total mileage of the Chinese high-speed railway. The box girder structure has many natural modes of low frequencies, which can be excited by a train passing at high speed, generating low-frequency bridge noise. This paper is concerned with the prediction of such bridge noise and reports a prediction model. The model, as other existing models of the same nature, also incorporates two parts, one dealing with vehicle-track-viaduct dynamics and the other dealing with sound radiation from the girders, but takes into account more features related to high speed. In this model, vehicle-track-viaduct dynamics is dealt with in the frequency-domain based on the theory of infinitely long periodic structure and the Fourier-series method, predicting vibration frequency spectra for each and every box girder. The predicted vibration frequency spectra of all the box girders are expressed as a sum of propagating waves at different wavenumbers, and sound radiation from each propagating wave is evaluated using the 2.5D acoustic boundary element method. This approach to sound radiation enables contributions from all the box girders to be included at a reasonable computational cost. The paper continues with a comparison in bridge vibration and noise between prediction and measurement for a typical site. And finally, based on the parameters of that site, characteristics of noise radiation from the concrete box girders are studied using the prediction model.