Infrasound and Low Frequency Noise in the Passenger Compartment of Vehicles

1997 ◽  
Vol 16 (4) ◽  
pp. 219-227 ◽  
Author(s):  
Helmut Spannheimer ◽  
Raymond Freymann
Keyword(s):  
Mathematical Model ◽  
Low Frequency ◽  
Experimental Investigations ◽  
Frequency Noise ◽  
Simple Mathematical Model ◽  
Low Frequency Noise ◽  
Acoustic Response ◽  
Frequency Range ◽  
Passenger Compartment

The acoustic response determined in the passenger compartment of a vehicle is characterized by resonances in the infrasound and low frequency range. A simple mathematical model is derived allowing the numerical identification of the related low frequency acoustic eigenmodes. The numerically obtained results are verified on the basis of experimental investigations.

scholarly journals Low Frequency Noise Remove from EEG Signal

2020 ◽  
Vol 9 (1) ◽  
pp. 1510-1513
Keyword(s):  
Human Brain ◽  
Random Noise ◽  
Low Frequency ◽  
Frequency Noise ◽  
Eeg Signal ◽  
Low Frequency Noise ◽  
Frequency Range ◽  
Average Value ◽  
Different Types ◽  
The Brain

The electrical activity of the brain recorded by EEG which used to detect different types of diseases and disorders of the human brain. There is contained a large amount of random noise present during EEG recording, such as artifacts and baseline changes. These noises affect the low -frequency range of the EEG signal. These artifacts hiding some valuable information during analyzing of the EEG signal. In this paper we used the FIR filter for removing low -frequency noise(<1Hz) from the EEG signal. The performance is measured by calculating the SNR and the RMSE. We obtained RMSE average value from the test is 0.08 and the SNR value at frequency(<1Hz) is 0.0190.

Low-frequency noise control using layered granular aerogel and limp porous media

2021 ◽  
Vol 263 (4) ◽  
pp. 2724-2729
Author(s):  
Yutong Xue ◽  
Amrutha Dasyam ◽  
J. Stuart Bolton ◽  
Bhisham Sharma
Keyword(s):  
Noise Control ◽  
Glass Fibers ◽  
Low Frequency ◽  
Normal Incidence ◽  
Frequency Noise ◽  
Fibrous Materials ◽  
Low Frequency Noise ◽  
Frequency Range ◽  
Fibrous Media ◽  
Impedance Tube Method

The acoustic absorption of granular aerogel layers with a granule sizes in the range of 2 to 40 μm is dominated by narrow-banded, high absorption regions in the low-frequency range and by reduced absorption values at higher frequencies. In this paper, we investigate the possibility of developing new, low-frequency noise reduction materials by layering granular aerogels with traditional porous sound absorbing materials such as glass fibers. The acoustic behavior of the layered configurations is predicted using the arbitrary coefficient method, wherein the granular aerogel layers are modeled as an equivalent poro-elastic material while the fibrous media and membrane are modeled as limp media. The analytical predictions are verified using experimental measurements conducted using the normal incidence, two-microphone impedance tube method. Our results show that layered configurations including granular aerogels, fibrous materials, and limp membranes provide enhanced sound absorption properties that can be tuned for specific noise control applications over a broad frequency range.

Impact of Proton Irradiation on Power 4H-SiC MOSFETs

2020 ◽  
Vol 1004 ◽  
pp. 1074-1080
Author(s):  
Alexander A. Lebedev ◽  
Vitalii V. Kozlovski ◽  
Leonid Fursin ◽  
Anatoly M. Strel'chuk ◽  
Mikhail E. Levinshtein ◽  
...  
Keyword(s):  
Proton Irradiation ◽  
Removal Rate ◽  
Low Frequency ◽  
Frequency Noise ◽  
Electrical Characteristics ◽  
Low Frequency Noise ◽  
Frequency Range ◽  
Maximum Value ◽  
Noise Spectroscopy ◽  
Noise Density

Impact of 15 MeV proton irradiation on electrical characteristics and low frequency noise has been studied in high-power vertical 4H-SiC MOSFETs of 1.2 kV-class at doses 1012 £ F £ 1014 cm-2. The maximum value of the field-effect mobility µFЕ depends weakly on F up to F = 2×1013 cm-2. At F = 4×1013 cm-2, the character of the µFЕ(Vg) dependence changes radically. The maximum µFЕ decreases approximately threefold. The dose Fcr corresponding to the complete degradation of the device is about 1014 cm-2. It can be estimated as Fcr» he/n0, where he is the electron removal rate and n0 is the initial electron concentration in the drift layer. In the entire frequency range of analysis f, gate voltages, and drain-source biases, the frequency dependence of the current spectral noise density SI(f) follows the law SI ~ 1/f. From the data of noise spectroscopy, the density of traps in the gate oxide Ntv has been estimated. In non-irradiated structures, Ntv » 5.4×1018 cm-3eV-1. At Ф = 6×1013 cm-2, the Ntv value increases to Ntv » 7.2×1019cm-3eV-1. The non-monotonic behavior of the output current Id and the level of low frequency noise on dose F has been demonstrated.

RESEARCH AND MAPPING OF LOW FREQUENCY NOISE GENERATED BY POWER PLANTS OF INDUSTRIAL ENTREPRISES

Akustika ◽  
2021 ◽  
pp. 103
Author(s):  
Andrey Vasilyev
Keyword(s):  
Power Plants ◽  
Low Frequency ◽  
Environmental Noise ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Frequency Range ◽  
Noise Mapping ◽  
Industrial Enterprises ◽  
Noise Measurements ◽  
Urban Territory

Environmental noise level from industrial enterprises is constantly increasing, especially in low frequency range. This paper presents the results of research and mapping of low frequency noise generated by power plants of industrial enterprises. Environmental noise mapping results of urban territory of Samara region of Russia are also presented. Results of noise measurements during industrial enterprises operation (on the example of “KuibyshevAzot” company) are showing that in some measuring points there were exceeding values compared with Russian sanitary norms requirements. The most serious problem is low frequency noise impact.

Theoretical and Experimental Study on Phononic Crystal Structures for Low-Frequency Noise Reduction in the Brake

2013 ◽  
Author(s):  
Li Shen ◽  
Jiu Hui Wu
Keyword(s):  
Noise Reduction ◽  
Phononic Crystal ◽  
Low Frequency ◽  
Equivalent Model ◽  
Frequency Noise ◽  
Steel Matrix ◽  
Two Dimensional ◽  
Low Frequency Noise ◽  
Frequency Range ◽  
Extremely Low Frequency

Phononic crystal is an artificial periodic structure in which elastic constants distribute periodically. In this paper, a two dimensional Bragg scattering phononic crystal was introduced into low-frequency noise reduction facility in the brake originally. Through the theoretical analysis by using Plane-wave Expansion Method to obtain the band diagram of a phononic crystal with holes periodically arranged in the 45 carbon steel plate and establishing the equivalent model in motion as the brake, we find an approximate bandgap between 0–5400Hz in the low-frequency range while the complete static bandgaps are distributed in the high-frequency range. It is believed that this kind of extremely low-frequency bandgap is due to the combination of the vibration of a single scatter and the interaction among scatters. In order to demonstrate the theory, contrastive experiment was taken. Noise spectrum diagram of the origin plate without holes was obtained in the first experiment. According to the equivalent model, the two dimensional air column/steel matrix phononic crystal structure in which filling rate was 40% was designed to apply in the test apparatus so that the frequency range (2050 to 2300Hz) of strong noise would be involved in this bandgap. Moreover, the noise in the whole frequency range (0–2550Hz) went down. This phenomenon proved that experiment result was coincident with theoretic consequence. The maximum decreasing amplitude of the noise reached as much as 25dB and the average decreasing amplitude was about 13dB from 2050 to 2300 Hz. In a word, this bandgap which is the combination effect of structure periodicity or the Mie scattering has an obvious extremely low-frequency characteristic in noise and vibration control in the brake.

scholarly journals Frequency weighting to evaluate the feeling of pressure and/or vibration caused by low-frequency noise: Re-analysis of an existing study

2021 ◽  
pp. 146134842110421
Author(s):  
Junta Tagusari ◽  
Sho Sato ◽  
Toshihito Matsui
Keyword(s):  
Mathematical Model ◽  
Health Effects ◽  
Broad Band ◽  
Multivariate Logistic Regression Analysis ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Exposure Response ◽  
Frequency Weighting ◽  
The Mathematical Model

Low-frequency noise may create specific perceptions, which might cause various health effects. The present study aimed to identify exposure–response relationships between low-frequency noise and perceptions by re-analysing an experimental study. We investigated the predominant perceptions of ‘feeling bothered’ and ‘feeling of pressure and/or vibration’ using multivariate logistic regression analysis. A significant interaction between 1/3 octave-band sound pressure level and frequency was indicated for ‘feeling bothered’ but not ‘feeling of pressure and/or vibration’, suggesting that the ‘feeling of pressure and/or vibration’ does not originate in cochlear. A mathematical model indicating resonance at approximately 50 Hz fitted the results well. A frequency weighting derived from the mathematical model could be applied to broad-band low-frequency noise to evaluate the perception and health effects. However, further investigations on the weighting for the perception are necessary because the results were obtained only from the existing study.

scholarly journals Features of time variations of microseismic noise at seismic stations in Tajikistan

2021 ◽  
Vol 3 (4) ◽  
pp. 18-37
Author(s):  
Vladimir Zhuravlev ◽  
Albert Lukk
Keyword(s):  
High Frequency ◽  
Noise Level ◽  
Low Frequency ◽  
Frequency Noise ◽  
Noise Amplitude ◽  
Low Frequency Noise ◽  
Frequency Range ◽  
Seismic Stations ◽  
High Frequency Noise ◽  
40 Hz

The spectral structure of microseismic noise in the frequency range of 0.01-40 Hz at different times of the day and year, recorded by broadband equipment at eight IRIS group seismic stations in Tajikistan in 2005-2020, was analyzed. Two disjoint frequency ranges are distinguished, which we conditionally call "high-frequency" (2-40 Hz) and "low-frequency" (0.01-0.75 Hz) noise, separated by a natural drop in the noise amplitude to 20-30 Db. It is assumed that the high-frequency range of noise has a local nature, due to exogenous sources of natural origin in the form of wind gusts, concussions from powerful watercourses and fluctuations in the level of large reservoirs, as well as man-made in-terference due to road and quarry explosions, the work of large industrial enterprises and concussions from road traffic. Low-frequency noise is most likely caused by global storm microseisms. High-frequency noise has a well-defined daily frequency, which is completely absent in low-frequency noise. At the same time, in both frequency ranges, the existence of a clearly pronounced seasonal peri-odicity has been established, the amplitude of which reaches 6-7 Db for high-frequency noise and about half as much for low-frequency noise. However, at the same time, the seasonal frequency of high frequency and low-frequency noise turns out to be antiphase, which indicates in favor of the different genesis of these two components of microseismic noise. The amplitude of the diurnal periodicity in variations of the high-frequency noise level is maximal during the daytime, remaining approximately constant for 8-10 hours. At the same time, the decline in the noise amplitude in the evening lasts longer than the steeper morning growth. The time intervals of a sharp increase and decrease in the intensity of the discussed daily extreme are quite well correlated, respectively, with morning and evening twilight at different times of the year. This is reflected in the wider flat part of the maximum noise level in summer compared to winter and the differences in its level up to 6 Db in favor of summer time. This observation can be considered as a manifestation of the deep influence of the Sun on the oscillatory processes that generate high-frequency microseismic noise.

Study of Sound Insulation of Control Cabins in Industry in the Low Frequency Range

1992 ◽  
Vol 11 (2) ◽  
pp. 42-46
Author(s):  
Anna Kaczmarska ◽  
Danuta Augustyriska
Keyword(s):  
Noise Reduction ◽  
Sound Pressure ◽  
Low Frequency ◽  
Machine Building ◽  
Sound Insulation ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Frequency Range ◽  
Sound Pressure Levels ◽  
Lower Frequencies

The number of control cabins installed in industry has increased considerably during the last few years. Most cabins installed nowadays show a satisfactory noise reduction in the frequency range above 500 Hz. The effect of noise damping however shows a gradual decrease for lower frequencies. The present paper is a description of the distribution of low frequency noise in different types of control cabins installed in typical low frequency noise environments in steel plants and the machine building industry. Measurements were made in 20 control cabins, constructed of metal and stone Measurements of sound pressure levels in octave bands were made inside and outside the cabins. The sound pressure level in octave bands in the low frequency range (4–31.5 Hz) inside the cabins was high and varied between 60–108 dB. This is probably due to the insufficient noise reduction for lower frequencies. In some control cabins there was an increased level of low frequency noise inside the cabin compared to the outside. In these control cabins sound pressure levels exceed the admissible values according to Polish standards. The increase of noise level within the low frequency range is considered to be based on resonances.

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