Random nature of corona processes in UHV power lines and the accompanying noise is the reason that in practice the best determination of acoustic parameters, necessary for the noise evaluation, is obtained from the continuous monitoring procedure. However because of considerable fluctuations (both the useful signal part and the interfering components), careful selection of monitored parameters is necessary to enable a possibility of automatic determination of the parameters that are required for long-term evaluation of corona noise. In the present work a practical realization is shown for estimation of corona noise parameters, based on the data obtained from continuous monitoring stations, making use of the statistical spectra measurement and characteristic features of corona process acoustic signal. Selected results are presented from continuous monitoring of corona noise generated at a 400 kV power line, with special attention focused on definitions of the measured quantities, which enable automatic estimation of the basic factors required for noise evaluation. Accompanying monitoring of environmental conditions, including humidity, precipitation intensity and fog density, that are well correlated with the corona process intensity, which might definitely increase the filtration efficiency of environmental disturbances and on the other hand, it enables verification of calculation methods applied to corona noise. The paper also contains a description of practical approach to selection signal parameters of corona noise in continuous monitoring stations.
The paper presents the current state of knowledge concerning the sources of noise generated by wind turbines, force measurement methodology, and assessment of noise onerousness in this type of installation, on the basis of a study concerning a wind farm with five REpower MM92 wind turbines and the electric power of 2 MW and the sound power level of 104.2 dB(A) each. Particular attention was focused on the often discussed problem of presence of infrasound generated by turbines and on the requirements of the applicable reference methodologies for the measurement of wind speed to 5 m/s, while the turbine reaches its full power at speeds above 10 m/s.
New Year’s Eve is an example of a situation in which urban residents are exposed to an almost continuous and increased noise level from the impulsive sounds sources – fireworks. This custom has become a source of many controversies related to the protection of human and animal health or environmental pollution. However, current legal regulations only slightly affect the subject of noise of fireworks and its harmfulness. Currently, it does not seem possible to completely prohibit the use of fireworks in urban areas, but this does not mean that it is not possible to decrease the degree of their annoyance. The paper consists the issues of identification, analysis and assessment of impulsive noise of fireworks and acoustic climate during New Year’s Eve. Material presented refers to measurements of time series, frequency spectrum and values of noise parameters of selected fireworks. It was presented, among others, that the measured values exceed the criteria for occupational noise (LCpeak), due to the direct hazard of hearing loss, from 1.8 dB at a distance of 25 m and 6.2 dB at a distance of 15 m. Also this work discusses results of impulsive noise measurements of fireworks recorded during New Year’s Eve in years 2016–2017. Material refers to measurements at three measurement points spread over the city of Kraków. Obtained results were compared with typical noise levels for night time in urban area, indicating also the main sources of annoyance and hazard from this type of noise.
The paper presents the results of numerical analysis of the SAW gas sensor in the steady and non-steady states. The effect of SAW velocity changes vs surface electrical conductivity of the sensing layer is predicted. The conductivity of the porous sensing layer above the piezoelectric waveguide depends on the profile of the diffused gas molecule concentration inside the layer. The Knudsen’s model of gas diffusion was used. Numerical results for the effect of gas CH4 on layers: WO3, TiO2, NiO, SnO2 in the steady state and CH4 in the non-steady state in recovery step in the WO3 sensing layer have been shown. The main aim of the investigation was to study thin film interaction with target gases in the SAW sensor configuration based on simple reaction-diffusion equation. The results of the numerical analysis allow to select the sensor design conditions, including the morphology of the sensor layer, its thickness, operating temperature, and layer type. The numerical results basing on the code elaborated numerical system (written in Python language), were analysed. The theoretical results were verified and confirmed experimentally.