Noise Characteristics of Tungsten Circular Blade During Sawing of Medium Density Fiberboard

2021 ◽  
Vol 13 (9) ◽  
pp. 1781-1788
Author(s):  
Zhao-Long Zhu ◽  
Wei-Hang Dong ◽  
Xiao-Dong (Alice) Wang ◽  
Xiao-Lei Guo ◽  
Zhan-Wen Wu
Keyword(s):  
Noise Level ◽  
Medium Density Fiberboard ◽  
Low Noise ◽  
Noise Power ◽  
Positive Contribution ◽  
Medium Density ◽  
Noise Characteristics ◽  
Excited Vibration ◽  
Circular Saws ◽  
Whistling Noise

This work deals with the noise generated from sawing processes of medium density fiberboard, where special attention was given to the changes in sawing noise at different cutting conditions when using circular saws with varied radial slots. The experimental results gave the following insights: The noise level in idling is positively related to the spindle speed. According to the noise power spectra, whistling noise is found during sawing processes, which is mainly caused by self-excited vibration of saw, and it had directivity. Furthermore, the radial slots have a different positive contribution to the noise reduction during idling, but has limited effect on the noise in cutting. In order to reduce the noise pollution induced by sawing, it was proposed to use circular saws with radial slots and copper plugged in its bottom for sawing of medium density fiberboard, in respect to low noise level and avoiding whistling noise.

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>

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.

Study on Noise in New Roller Chain Drives

2012 ◽  
Vol 522 ◽  
pp. 598-601
Author(s):  
Wei Sun ◽  
Xiao Lun Liu ◽  
Wen Cheng Wang ◽  
Li Yan He ◽  
Jia Jun Liu
Keyword(s):  
Noise Reduction ◽  
Noise Level ◽  
High Speed ◽  
Low Noise ◽  
The Other ◽  
Metal Mesh ◽  
Roller Chain ◽  
Polyurethane Composite ◽  
Noise Characteristics ◽  
The Impact

In order to mitigate the impact and the polygon effect of the chain and the sprocket during the meshing process and achieve the purpose of noise reduction, a Hlow noiseH nanostructured metal mesh-polyurethane composite material split roller chain was designed by means of changing structure and material of chain roller. Noise testing and frequency spectrum analysis were conducted, for the new roller chain and the other three kinds of the same specification chains with different structural rollers, on the closed force flow noise test bench researched and developed independently. The results show that the new roller chain can absorb some of the impact energy, and reduce vibration and noise of chain drive. The noise level generated by the new roller chain is significantly lower than the other tested roller chains, especially in high frequency and high speed. The difference in noise level is actually 3-11dB in driving sprocket speed of 1000r/min, and a significant noise reduction is achieved. The results also verify low noise characteristics of the new roller chain and rationality of design method.

Test and Analysis of Bush Roller Chains for Noise Reduction

2011 ◽  
Vol 52-54 ◽  
pp. 430-435
Author(s):  
Xiao Lun Liu ◽  
Wei Sun ◽  
Song Ding ◽  
Jian Fang Liu ◽  
Yu Ying Wang ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Impact Energy ◽  
Noise Level ◽  
Low Noise ◽  
Working Environment ◽  
The Other ◽  
Chain Drive ◽  
Noise Characteristics ◽  
Testing Data ◽  
Different Types

A low noise duplex bush chains with split rollers was developed through changing roller structure to reduce noise of bush roller chains. The split rollers could absorb more impact energy, mitigate meshing impact and reduce chain drive noise. The noise generated by different types of duplex bush roller chains was carried out to test in same speed, low noise characteristics of duplex sleeve chains with split rollers was verified. By analysis of testing data, noise level of duplex sleeve chains with split rollers compared with that of the other duplex bush roller chains was reduced by the average 3 ~ 8dB, and low 10 ~ 13dB than that of 16A simplex sleeve roller chains. The chains made chain drive significantly improve in the working environment, with steady transmission, strong bearing, low noise, and a significant noise reduction was achieved.

Low-noise hybrid frequency synthesizers based on direct digital and direct analog synthesis

2020 ◽  
pp. 51-56
Author(s):  
Vladimir V. Romashov ◽  
Kirill A. Yakimenko ◽  
Andrey N. Doktorov ◽  
Lubov V. Romashova
Keyword(s):  
Phase Noise ◽  
Frequency Synthesizers ◽  
Low Noise ◽  
Synthesis Methods ◽  
Noise Power ◽  
Frequency Synthesis ◽  
Noise Characteristics ◽  
Analog Synthesis ◽  
Hybrid Frequency ◽  
Offset Frequency

The research of the possibility of using hybrid frequency synthesizers based on direct digital and direct analog methods of frequency synthesis as heterodynes of modern spectrum analyzers constructed according to the superheterodyne scheme is presented. The main advantages of such synthesizers over traditionally used heterodyne schemes based on direct digital and indirect frequency synthesis methods are shown. The requirements for the heterodynes of the first mixing stages of spectrum analyzers are presented. A block diagram of a wideband heterodyne generating a frequency range from 4000 MHz to 8000 MHz with a step not exceeding 1 Hz is proposed. Formulas for calculating the main frequency ratios in the structure of the heterodyne have been developed. A mathematical model of phase noise power spectral density (PSD) depending on the offset frequency from the carrier is developed. The noise characteristics of the proposed scheme are studied using the model. It is determined that at the output frequency of the heterodyne equal to 4521,4 MHz, the level of phase noise PSD is: minus 90 dBc/Hz at the offset frequency equal to 100 Hz; minus 140 dBc/Hz at the offset frequency equal to 100 kHz. It is shown that the hybrid synthesizer based on direct digital and direct analog synthesis methods has an advantage in the level of phase noise from 5 to 30 dB over the low-noise heterodynes of modern spectrum analyzers at frequencies above 1 kHz from the carrier. Additional advantages of the proposed scheme are a simple architecture, low power consumption and high frequency tuning speed due to the absence of phaselocked loops in the structure of the heterodyne.

scholarly journals CALCULATION OF THE NOISE LEVEL FROM A LINEAR SOURCE WITH VARIABLE NOISE CHARACTERISTICS ALONG THE LENGTH

Akustika ◽  
2019 ◽  
Vol 32 ◽  
pp. 64-66
Author(s):  
Vladimir Tupov
Keyword(s):  
Noise Level ◽  
Practical Interest ◽  
Low Noise ◽  
Sound Level ◽  
Linear Source ◽  
Noise Characteristics ◽  
Real Objects ◽  
Distribution Station ◽  
Radiated Sound ◽  
Theoretical Issues

Calculation issues from linear sources are well studied. At the same time, the theoretical issues of calculating the noise level from a linear source of finite length with variable noise characteristics along the length have not been sufficiently studied so far. This article deals with the case when the radiated sound energy along the length of a linear source is not constant but varies along its length. The solution of the equation is given, which makes it possible in general to calculate sound pressure levels (sound level) at a distance from a linear source with variable noise characteristics along its length. The task has of practical interest. For example, this concerns the calculation of noise from a gas pipeline after a gas distribution station (GDS). The main source of GDS is valve noise. Noise from it radiates along the length of the pipeline. In this case, the noise from it along the length of the pipeline decreases. The distance from pipeline is a constant. Noise from the flow velocity of gas in the channel is made substantially less noise than the valve’s noise. This assumption is true for most real objects. The resulting formula allows you to make the necessary decisions to create a low-noise object and select the necessary measures for its sound attenuation.

scholarly journals Calcium carbonate modified urea–formaldehyde resin adhesive for strength enhanced medium density fiberboard production

RSC Advances ◽  
2021 ◽  
Vol 11 (40) ◽  
pp. 25010-25017
Author(s):  
Li Lu ◽  
Yan Wang ◽  
Tianhua Li ◽  
Supeng Wang ◽  
Shoulu Yang ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Urea Formaldehyde ◽  
Medium Density Fiberboard ◽  
Urea Formaldehyde Resin ◽  
Formaldehyde Resin ◽  
Medium Density ◽  
Ionic Bond ◽  
Resin Adhesive ◽  
Uf Resin ◽  
Modified Urea

Reactions between CaCO3 and CH2O2 during polycondensation of UF resin produce Ca2+. Ionic bond complexation binds Ca2+ with UF resin. The UF resin crystalline percentage decreases from 26.86% to 22.71%. IB strength of resin bonded fiberboard increases from 0.75 to 0.94 MPa.

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