scholarly journals Preliminary analysis on the noise characteristics of MWISP data

2022 ◽  
Vol 21 (12) ◽  
pp. 304
Author(s):  
Jia-Jun Cai ◽  
Ji Yang ◽  
Sheng Zheng ◽  
Qing-Zeng Yan ◽  
Shao-Bo Zhang ◽  
...  
Keyword(s):  
Normal Distribution ◽  
Millimeter Wave ◽  
Edge Effects ◽  
Noise Level ◽  
Preliminary Analysis ◽  
Molecular Line ◽  
Noise Characteristics ◽  
Noise Structure ◽  
Skewed Normal Distribution ◽  
Major Factors

Abstract Noise is a significant part within a millimeter-wave molecular line datacube. Analyzing the noise improves our understanding of noise characteristics, and further contributes to scientific discoveries. We measure the noise level of a single datacube from MWISP and perform statistical analyses. We identified major factors which increase the noise level of a single datacube, including bad channels, edge effects, baseline distortion and line contamination. Cleaning algorithms are applied to remove or reduce these noise components. As a result, we obtained the cleaned datacube in which noise follows a positively skewed normal distribution. We further analyzed the noise structure distribution of a 3D mosaicked datacube in the range l = 40 ⋅ ° 7 to 43 ⋅ ° 3 and b = − 2 ⋅ ° 3 to 0 ⋅ ° 3 and found that noise in the final mosaicked datacube is mainly characterized by noise fluctuation among the cells.

Effects of Diffuser Vane Geometries on Compressor Performance and Noise Characteristics in a Centrifugal Compressor

2013 ◽  
Author(s):  
Yohei Morita ◽  
Nobumichi Fujisawa ◽  
Takashi Goto ◽  
Yutaka Ohta
Keyword(s):  
Centrifugal Compressor ◽  
Noise Level ◽  
Leading Edge ◽  
Broadband Noise ◽  
Frequency Noise ◽  
Numerical Techniques ◽  
Vaned Diffuser ◽  
Noise Characteristics ◽  
Edge Vortex ◽  
Compressor Performance

The effects of the diffuser vane geometries on the compressor performance and noise characteristics of a centrifugal compressor equipped with vaned diffusers were investigated by experiments and numerical techniques. Because we were focusing attention on the geometries of the diffuser vane’s leading edge, diffuser vanes with various leading edge geometries were installed in a vaned diffuser. A tapered diffuser vane with the tapered portion near the leading edge of the diffuser’s hub-side could remarkably reduce both the discrete frequency noise level and broadband noise level. In particular, a hub-side tapered diffuser vane with a taper on only the hub-side could suppress the development of the leading edge vortex (LEV) near the shroud side of the diffuser vane and effectively enhanced the compressor performance.

Research on Star Subdivision Location Method Based on Skewed Normal Distribution

2016 ◽  
Vol 53 (5) ◽  
pp. 051002
Author(s):  
贾瑞明 Jia Ruiming ◽  
马晓蕾 Ma Xiaolei ◽  
郝云彩 Hao Yuncai
Keyword(s):  
Normal Distribution ◽  
Location Method ◽  
Skewed Normal Distribution

Evaluation of Noise Characteristics of Drainage and Water Supply Systems in Apartment Bathrooms

2014 ◽  
Vol 1025-1026 ◽  
pp. 987-990
Author(s):  
Jun Oh Yeon ◽  
Kyoung Woo Kim ◽  
Kwan Seop Yang ◽  
Byung Kwon Lee
Keyword(s):  
Water Supply ◽  
Noise Level ◽  
Drainage System ◽  
Low Noise ◽  
Sound Level ◽  
Water Supply Systems ◽  
Apartment Building ◽  
Noise Characteristics ◽  
Measurement Results ◽  
Supply Systems

We have developed a low-noise drainage system, which was installed in bathrooms of apartment building units as well as in a mock-up test building, to evaluate the noise level in order to reduce the noise produced in the bathrooms of multiunit dwellings. The drainage system installed in the mock-up building consists of six types of detachable drains, and the level of noise produced during toilet use in the upper unit was measured in the lower unit. The measurement results showed that low-noise drainage 4 exhibited the Leq(equivalent continuous sound level) at 34.7 dB(A). The noise measurement results of various types of low-noise drains installed in an apartment building showed that the Leqduring toilet use was 46.7 dB(A) on average, and the Leqduring sink use was 40.5 dB(A) on average.

scholarly journals Analysis of Skid Resistance and Noise Characteristics for Varieties of Concrete Pavement

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Jinmiao Fang ◽  
Jinsong Tu ◽  
Kunming Wu
Keyword(s):  
Noise Level ◽  
Evaluation Criteria ◽  
Sound Intensity ◽  
Low Noise ◽  
Concrete Pavement ◽  
Skid Resistance ◽  
Concrete Pavements ◽  
Noise Levels ◽  
Cement Concrete ◽  
Noise Characteristics

To establish evaluation criteria for the pavement skid resistance and noise level in tunnels pavements, the zoning and control standards for skid resistance and concrete pavement noise were examined. Transverse friction coefficient (TFC) test equipment and the on-board sound intensity (OBSI) method were used to evaluate the antisliding characteristics and noise levels of several tunnel pavements. The results indicated poor antisliding characteristics and noise levels in ordinary grooved cement concrete pavement, whereas new types of cement concrete pavements, such as exposed concrete pavements and polymer-modified cement concrete pavements, had good antisliding characteristics and achieved low noise levels. Combined with the cluster analysis method, a zoning method for the antisliding and noise level in concrete pavement is proposed. The antisliding characteristics and noise levels of the pavement are divided into three zones. To ensure safety and comfort during driving, the antisliding value (SFC) of the tunnel pavement should be more than 50, and the noise level should not exceed 105 dB. Finally, the correlation between the antisliding and noise levels for pavement was analyzed. The results indicated that the antiskiding value of pavement has a strong correlation to the noise level.

Seismic noise characteristics in Chinese mainland

2020 ◽  
Author(s):  
Fang Wang ◽  
Weitao Wang ◽  
Jianfeng Long ◽  
Leiyu Mu
Keyword(s):  
Noise Level ◽  
Seismic Noise ◽  
Vertical Component ◽  
Chinese Mainland ◽  
Low Noise ◽  
Noise Characteristics ◽  
Power Spectral ◽  
Short Period ◽  
Power Spectral Densities ◽  
Noise Models

<p>Using the three-component continuous waveform recordings of 880 broadband seismic stations in China Seismic Network from January 2014 to December 2015, we calculated power spectral densities and probability density functions over the entire period for each station，and  investigated the characteristics of seismic noise in Chinese mainland. The deep analysis on the vertical recordings  indicates that the spatial distribution of noise levels is characterized by obvious zoning for different period bands.  Densely populated areas have higher short-period noise level than sparsely populated ones, suggesting that short-period noise is related to the intensity distribution of human activities such as transportation and industry. Meanwhile，the short-period noise level near the basin is higher than the mountainous areas，which is probably caused by the amplification effect of the sedimentary layer. The microseism energy  gradually decreases from the southeastern coastal lines to the inland regions. Furthermore, horizontal-component noise level  showed a striking constrast with the vertical component at microseismic and long-period bands. In consideration of  the zoning chracteristics and the need of seismic observations, high and low noise models were  acquired for each network , which were proved to be a more effective tool to identify locally abnormal signals including earthquake, instrumental error and various distrubance compared with the global new high and low model. </p>

The influence of noise in vehicles on the driver’s subjective evaluation of driveability

2017 ◽  
Vol 232 (11) ◽  
pp. 1494-1500
Author(s):  
Hyoseong Wi ◽  
Jinil Park ◽  
Jonghwa Lee
Keyword(s):  
Fuel Economy ◽  
Noise Level ◽  
Subjective Evaluation ◽  
Engine Performance ◽  
Operating Conditions ◽  
Vehicle Noise ◽  
Noise Characteristics ◽  
Noise Frequency ◽  
Influence Of Noise ◽  
Physical Quantities

Driveability, including maneuverability, stability, and riding quality, is one of the most important factors determining the marketability of vehicles. However, unlike fuel economy or engine performance, driveability is very difficult to be evaluated quantitatively. With regard to research on vehicle noise related to driveability, existing works mainly deal with quantification or improvement methods. In this study, the various physical quantities regarding vehicle operating conditions were measured and the noise characteristics were manipulated in several ways to evaluate and analyze the influence of noise on subjective drivability. The results show that the noise level as well as noise frequency characteristics are influencing the drivers’ subjective evaluation of driveability.

Studies on Scroll Compressor Noise Improvement

2014 ◽  
Vol 694 ◽  
pp. 504-508
Author(s):  
Qing Miao ◽  
Yan Ru Men ◽  
Jin Xiang Wu ◽  
Xiang Gou
Keyword(s):  
Intensity Distribution ◽  
Noise Level ◽  
Sound Intensity ◽  
Specific Method ◽  
Test Results ◽  
Scroll Compressor ◽  
Root Cause ◽  
Additional Weight ◽  
Noise Characteristics ◽  
Noise Test

As the environment and customer are sensitive to compressor noise from refrigeration air condition system, it’s necessary to reduce noise level for scroll compressor to compete with piston one in this field. In this paper, we studied one way to detect noise resource and reduce noise level for scroll compressor; analyzed its vibration and noise characteristics; got the sound intensity distribution on the surface of compressor; performed the model test of the main part by using hammer strike and gained their intrinsic frequents. At last, by comparing the scroll compressor noise test results, sound intensity distribution, and intrinsic frequents, it was confirmed that upper shell resonation is the root cause to increase the noise. Also we gave a specific method, adding additional weight to upper shell, to avoid resonation. It’s proved to be efficient after test check.

Experimental Investigations of Effects of Centrifugal Compressor Impeller Design on Noise Characteristics

2014 ◽  
Author(s):  
Kyoung-Ku Ha ◽  
Chang-ha Lee ◽  
Yong-sun Park ◽  
Shin-hyoung Kang ◽  
Chi-young Park ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Centrifugal Compressor ◽  
Noise Level ◽  
Processing System ◽  
Design Procedure ◽  
Low Noise ◽  
Design Flow ◽  
Normal Operation ◽  
Efficient Operation ◽  
Noise Characteristics

The subject of this study is a centrifugal compressor for fuel-cell vehicles which produces compressed air and sends it to the cathode channels of a fuel-cell stack. It uses up a lot of electricity and it is the only component in the processing system that has a rotating part moving a high angular velocity. So, it is important to improve the centrifugal compressor in efficiency and noise respects. As demand for quiet and comfort of vehicles increases recently, it becomes more and more important for the compressor to achieve low noise level. But it is difficult to design a suitable compressor with a conventional design method, which was formulated to provide highly efficient operation at the design point without considering the noise. Actually, the noise of a compressor is hard to be considered in the early steps of the design procedure because of a lack of information. So, this study aims to describe noise characteristics of centrifugal compressors experimentally and to pull noise considerations into a design procedure of the centrifugal compressor. According to previous studies, a tonal component leads to overall noise of a compressor in normal operation and there is a close connection between the instability intensity and the circumferential flow fluctuations of an impeller. Therefore an experimental study was designed to check the aero-acoustic characteristics of the impeller. An existing compressor was modified to install pressure transducers at the inlet and outlet of the impeller. And two microphones were installed to measure noise signals of the compressor in a sealed room. Tests were carried out to investigate the phenomena governing the overall noise and the dominant noise source of the centrifugal compressor. Then pressure fluctuations, noise signals and spectra of them were examined closely. After that, several impellers varying exit blade angles and design flow coefficients were tested also. They were all designed to satisfy the same pressure performance at a design mass-flow rate. Then investigations into the noise characteristics were carried out to find out effects of the impeller design variables on them. The results show that a large value of a blade angle is good for efficiency and noise level of the compressor. It is expected to be an optimal value to improve noise characteristics in terms of the design flow coefficient. The experimental facility, conditions and the results were described in this paper minutely.

scholarly journals The Statistical Properties of Sea Ice Velocity Fields

2017 ◽  
Vol 30 (13) ◽  
pp. 4873-4881 ◽  
Author(s):  
Sahil Agarwal ◽  
John S. Wettlaufer
Keyword(s):  
Sea Ice ◽  
White Noise ◽  
Time Scales ◽  
Velocity Fields ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Noise Characteristics ◽  
Noise Structure ◽  
Spatial Correlation Structure ◽  
Ice Velocity

By arguing that the surface pressure field over the Arctic Ocean can be treated as an isotropic, stationary, homogeneous, Gaussian random field, Thorndike estimated a number of covariance functions from two years of data (1979 and 1980). Given the active interest in changes of general circulation quantities and indices in the polar regions during the recent few decades, the spatial correlations in sea ice velocity fields are of particular interest. It is thus natural to ask, “How persistent are these correlations?” To this end, a multifractal stochastic treatment is developed to analyze observed Arctic sea ice velocity fields from satellites and buoys for the period 1978–2015. Since it was previously found that the Arctic equivalent ice extent (EIE) has a white noise structure on annual to biannual time scales, the connection between EIE and ice motion is assessed. The long-term stationarity of the spatial correlation structure of the velocity fields and the robustness of their white noise structure on multiple time scales is demonstrated; these factors (i) combine to explain the white noise characteristics of the EIE on annual to biannual time scales and (ii) explain why the fluctuations in the ice velocity are proportional to fluctuations in the geostrophic winds on time scales of days to months. Moreover, it is shown that the statistical structure of these two quantities is commensurate from days to years, which may be related to the increasing prevalence of free drift in the ice pack.

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