scholarly journals The effect of 2020 COVID-19 lockdown measures on seismic noise recorded in Romania

Solid Earth ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 2351-2368
Author(s):  
Bogdan Grecu ◽  
Felix Borleanu ◽  
Alexandru Tiganescu ◽  
Natalia Poiata ◽  
Raluca Dinescu ◽  
...  
Keyword(s):  
Noise Reduction ◽  
High Frequency ◽  
Urban Areas ◽  
Seismic Noise ◽  
Human Mobility ◽  
Vertical Component ◽  
World Health ◽  
High Frequency Range ◽  
Frequency Range ◽  
40 Hz

Abstract. After the World Health Organization declared COVID-19 a pandemic in March 2020, Romania followed the example of many other countries and imposed a series of restrictive measures, including restricting people's mobility and closing social, cultural, and industrial activities to prevent the spread of the disease. In this study, we analyze continuous vertical component recordings from the stations of the Romanian Seismic Network – one of the largest networks in Europe, consisting of 148 stations – to explore the seismic noise variation associated with the reduced human mobility and activity due to the Romanian measures against COVID-19 in detail. We focused our investigation on four frequency bands – 2–8, 4–14, 15–25 and 25–40 Hz – and found that the largest reductions in seismic noise associated with the lockdown correspond to the high-frequency range of 15–40 Hz. We found that all the stations with large reductions in seismic noise (>∼  40 %) are located inside and near schools or in buildings, indicating that at these frequencies the drop is related to the drastic reduction of human activity in these edifices. In the lower-frequency range (2–8 and 4–14 Hz) the variability of the noise reduction among the stations is lower than in the high-frequency range, corresponding to about 35 % on average. This drop is due to reduced traffic during the lockdown, as most of the stations showing such changes in seismic noise in these bands are located within cities and near main or side streets. In addition to the noise reduction observed at stations located in populated areas, we also found seismic noise lockdown-related changes at several stations located far from urban areas, with movement of people in the vicinity of the station explaining the noise reductions.

scholarly journals The effect of 2020 COVID-19 lockdown measures on seismic noise recorded in Romania

2021 ◽  
Author(s):  
Bogdan Grecu ◽  
Felix Borleanu ◽  
Alexandru Tiganescu ◽  
Natalia Poiata ◽  
Raluca Dinescu ◽  
...  
Keyword(s):  
Noise Reduction ◽  
High Frequency ◽  
Seismic Noise ◽  
Human Mobility ◽  
Vertical Component ◽  
World Health ◽  
High Frequency Range ◽  
Frequency Range ◽  
Noise Characteristics ◽  
40 Hz

Abstract. After the World Health Organization declared COVID-19 a pandemic in March 2019, Romania followed the example of many other countries and imposed a series of restrictive measures, including restricting people's mobility and closing social, cultural and industrial activities to prevent the spread of the disease. In this study, we analyze continuous vertical component recordings from the stations of the Romanian Seismic Network – one of the largest networks in Europe containing 148 stations – to explore in detail the seismic noise variation associated with the reduced human mobility and activity in Romania due to COVID-19. We focused our investigation on four frequency bands – 2–8 Hz, 4–14 Hz, 15–25 Hz and 25–40 Hz – and found that the largest reductions in seismic noise associated with the lockdown corresponds to the high frequency range, from 15 to 40 Hz. We found that all the stations with large reductions in seismic noise (> ~40 %) are located inside and near schools or in buildings, indicating that at these frequencies the drop is related to the drastic reduction of human activity in these edificies. In the lower frequency range (2–8 Hz and 4–14 Hz) the variability of the noise reduction among the stations is lower than in the high frequency range, and the noise level is reduced by up to 35 %. This drop is due to reduced traffic during the lockdown, as most of the stations showing such changes in seismic noise in these bands are located within cities, near main or side streets. In addition to the noise reduction observed at stations located in populated areas, we also found seismic noise lockdown-related changes at several stations located far from urban areas, with movement of people in the vicinity of the station explaining the noise reductions. Apart from the opportunity to investigate in more detail the seismic noise characteristics due to human mobility and activity, we show that noise reduction during the lockdown has also improved the earthquake detection capability of the accelerometers located in noisy urban environments.

Test and Analysis of Noise Reduction Effect for Different Heights and Distances of Sound Barrier

2011 ◽  
Vol 243-249 ◽  
pp. 4447-4450 ◽  
Author(s):  
Yan Liu ◽  
Bing Yang ◽  
Xiao Pai Zhang ◽  
Zhi Fang Zhong ◽  
Hua Xin Dong ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Sound Pressure Level ◽  
High Frequency ◽  
Sound Pressure ◽  
Pressure Level ◽  
High Frequency Range ◽  
Frequency Range ◽  
Sound Barrier ◽  
Test Points ◽  
Reduction Effect

Based on the comparative analysis on the low-noise road surface, noise reduction green belts, noise barriers and other noise reduction methods, the sound barrier is put forward as an important method for reducing the city road traffic noise. The noise reduction effects for different heights and different distances of the sound barrier are tested and analyzed through noise and vibration test and analysis system, the following conclusions can be drawn. At the same heights from the ground, the father the test points away from the noise barrier, the higher the sound pressure level will be; At the same distances from the sound barrier, the nearer the test points from the ground, the smaller the sound pressure level will be; All of the sound pressure level curves have basically the same variation trend and the main noise frequency band is from 160 to 1600Hz; In the high frequency range which is greater than 1600Hz, the sound pressure level decrease significantly, indicating that the sound barrier has better noise reduction effect for high frequency range. The results provide the basis for the design of the sound barriers.

Electromagnetic Property of La0.7Sr0.3MnO3/Ag Composite at High Frequency

2015 ◽  
Vol 655 ◽  
pp. 182-185
Author(s):  
Ke Lan Yan ◽  
Run Hua Fan ◽  
Min Chen ◽  
Kai Sun ◽  
Xu Ai Wang ◽  
...  
Keyword(s):  
High Frequency ◽  
Single Phase ◽  
Low Frequency ◽  
Electromagnetic Property ◽  
High Frequency Range ◽  
Frequency Range ◽  
Free Electron Concentration ◽  
Theoretical Simulation ◽  
Electrical And Magnetic Properties ◽  
Three Phase

The phase structure, and electrical and magnetic properties of La0.7Sr0.3MnO3(LSMO)-xAg (xis the mole ratio,x=0, 0.3, 0.5) composite were investigated. It is found that the sample withx=0 is single phase; the samples withx=0.3 and 0.5 present three phase composite structure of the manganese oxide and Ag. With the increasing of Ag content, the grain size of the samples increases and the grain boundaries transition from fully faceted to partially faceted. The permittivity of spectrum (10 MHz - 1 GHz) and the theoretical simulation reveal that the plasma frequencyfpincrease with Ag content, due to the increasing of free electron concentration, which is further supported by the enhancement of conductivity. While for the permeability (μr'), theμr'decrease with the increasing of Ag content at low frequency range (f< 20 MHz), while at the relative high frequency range (f> 300 MHz), theμr'increased with Ag content. Therefore, the introduction of elemental Ag resulted in a higherμr'at the relative high frequency range.

An Impedance-Based Approach for Rods With Shear-Type Damping Layer Treatment

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
P. W. Wang ◽  
D. Q. Zhuang
Keyword(s):  
High Frequency ◽  
Continuous Model ◽  
Damping Coefficient ◽  
System Response ◽  
Traditional Model ◽  
Constrained Layer Damping ◽  
High Frequency Range ◽  
Frequency Range ◽  
Shear Type ◽  
Shear Spring

An impedance-based approach for analyzing an axial rod with shear-type damping layer treatment is proposed. The rod and shear-type damping layer are regarded as two subsystems and both impedances are calculated analytically. The system impedance can be obtained through the impedance coupling between the host rod and the damping layer. The shear-type damping layer is regarded as a shear spring with complex shear modulus. Under the traditional model, the damping coefficient diminishes with the increasing frequency. The paper develops two shear-type damping layer models, including the single degree-of-freedom (SDOF) model and continuous model to predict the behavior of the damping layer. Both damping layer models are compared with the traditional model and the system responses from these models are validated by finite element method (FEM) code COMSOL Multiphysics. Results show that the damping coefficients of both the traditional shear-spring model and SDOF model diminish as the increasing frequency so that the system responses are discrepant with that from COMSOL in the high frequency range. On the other hand, the system response from the continuous model is consistent with that from COMSOL in the full frequency range. Hence, the continuous damping layer model can predict a correct damping coefficient in the high frequency range and this property can be also employed to improve the analysis of the constrained-layer damping treated structures. Finally, the modal loss factor and fundamental frequency of the system with respect to different damping layer thicknesses are presented using the developed approach.

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