noise

摘要： BACKGROUND Noise-induced hearing loss(NIHL)is the second most common acquired hearing loss following presbycusis.Exposure to recreational noise and minimal use of hearing protection increase the prevalence of NIHL in young females.NIHL is irreversible.Identifying minor hearing pathologies before they progress to hearing problems that affect daily life is crucial.AIM To compare the advantages and disadvantages of extended high frequency(EHF)and otoacoustic emission and determine an indicator of hearing pathologies at the early sub-clinical stage.METHODS This cross-sectional study was implemented in West China Hospital of Sichuan University from May to September 2019.A total of 86 participants,aged 18-22 years,were recruited to establish normative thresholds for EHF.Another 159 adults,aged 18-25 years with normal hearing(0.25-8 kHz≤25 dBHL),were allocated to low noise and noise exposure groups.Distortion otoacoustic emission(DPOAE),transient evoked otoacoustic emissions(TEOAE),and EHF were assessed in the two groups to determine the superior technique for detecting early-stage noise-induced pathologies.The chi-square test was used to assess the noise and low noise exposure groups with respect to extended high-frequency audiometry(EHFA),DPOAE,and TEOAE.P≤0.05 was considered statistically significant.RESULTS A total of 86 participants(66 females and 20 males)aged between 18 and 22(average:20.58±1.13)years were recruited to establish normative thresholds for EHF.The normative thresholds for 9,10,11.2,12.5,14,16,18,and 20 kHz were 15,10,20,15,15,20,28,and 0 dBHL,respectively.A total of 201 participants were recruited and examined for eligibility.Among them,159 adults aged between 18 and 25 years were eligible in this study.No statistical difference was detected between the noise exposure and the low noise exposure groups using EHFA,DPOAE,and TEOAE(P>0.05)except in the right ear at 4 kHz using TEOAE(abnormal rate 20.4%vs 5.2%,respectively;P=0.05).CONCLUSION These results showed TEOAE as the earliest indicator of minor pathology compared to DPOAE and EHFA.However,a multicenter controlled study or prospective study is essential to verify these results.

摘要： Objective Communities in the developing countries such as Ghana have little knowledge of effects of noise pollution on human health,which is demonstrated by their attitude towards this menace.This study assessed the health impacts of noise pollution and its spatial distribution in the Tarkwa Mining Community(TMC)of Ghana.Methods To achieve the study objective,questionnaires were administered;as well as collation of health data from major health centers in the study area.Noise levels were measured and noise map produced using geographic information system(GIS)techniques.Overlay maps of some diseases were done using overlay techniques in GIS.The noise exposure and corresponding noise doses for churches,working sites and social centers were also calculated using the respective formulae.Results The noise levels were found to be high above the prescribed Ghana Environmental Protection Agency(EPA)standards,with traffic noise levels ranging from 65.00 dBA to 98 dBA,while that of churches ranged from 73.10 dBA to 107.00 dBA and that of working sites from 74.4 dBA to 115.2 dBA.The calculated noise exposure and corresponding noise dose for churches ranged from 75.1 dBA to 104.6 dBA(i.e.,10%‒8000%),while that for workers’sites were from 75.8 dBA to 115 dBA(i.e.,12%‒90000%).Statistical regression and correlation analyses were done for diseases such as hypertension,ear problems and sleep disturbances.Conclusion The study has therefore revealed that the noise levels in the study area are very high and corresponding health impacts are prominent.Stakeholders and authorities should devise mitigating measures to combat this rising menace.The results revealed a strong positive correlation between noise and corresponding health impacts.Despite the positive correlation there are other causes and effects to the mentioned diseases.

摘要： Wind tunnel testing and embedded large eddy simulations are employed to study the noise reduction of trailing-edge finlets on an airfoil. Trailing-edge finlets are shown to increase the distance between the highly energetic fluid particles and the sharp trailing edge. Experiments were conducted at different angles of attack. Wind tunnel measurements confirm that finlets reduce the broadband noise radiated by the airfoil. Results also reveal that the noise reduction of finlets is dependent on the airfoil angle of attack, and that the highest noise reduction is obtained at the largest angle of attack tested.

摘要： Introduction: Noise-induced hearing loss is a preventable health problem worldwide. However, it continues to affect workers especially in the informal sector, due to the lack of medical and environmental monitoring. In Benin, millers are highly exposed. The objective of the study was to assess the hearing health situation of grain millers in the Dantokpa market in 2020. Methods: This was a cross-sectional study that included by exhaustive recruitment 57 millers. The data were collected using a standardized questionnaire followed by blood pressure measurements, noise levels and the performance of audiometries. Descriptive and univariate analysis was performed. Results: The sample consisted only of men. The median age was 25 years with extremes of 18 and 50 years. Noise levels at the workstation ≥ 85 dB (A) were obtained for 94.74% of the workers. No worker was wearing hearing protection equipment. The prevalence of hearing loss was 87.72% (95% CI = [76.32%;94.92%]) and that of occupational deafness was 29.82% (95% CI = [18.43% - 43.40%]) which was associated with age over 28 and high blood pressure. An awareness campaign with donation of hearing pads was carried out. Conclusion: Hearing loss is important among millers who do not benefit from any supervision because they are in the informal sector. A restructuring of this sector is necessary for the hearing health of workers.

摘要： NMR spectra acquired with experiments using frequency-sweeps such as the wide-band uniform-rate smooth truncation(WURST)spin-echo and Carr-Purcell-Meiboom-Gill(CPMG)sequences cannot be absorptively phased by using only conventional zerothand first-order phase correction.Implementation of phase correction up to the secondorder is described for obtaining absorptive spectra,which have more desirable line shapes and noise properties than magnitude spectra.The relationship of the second-order phase to the parameters of frequency sweeps is derived.The second-order phasing in the frequency-domain is equivalent to a point spread in the time-domain signal.The application of second-order phase correction is demonstrated with a wideline 35Cl CPMG spikelet spectrum.

摘要： Despite almost a century of studies dealing with traffic noise,researchers and practitioners still face old and new issues when designing a low-noise pavement.Given that,this manuscript aims at focusing on a number of unsolved questions,namely theoretical or technological.1)Is it viable to balance diverse road-related needs(i.e.,noise,expected life,texture levels,and friction)?2)How much does the pavement material affect its acoustic performance(the remaining factors being constant)?3)How much reliable is the relationship between road texture and mixture aggregate gradation?Based on the analysis of these issues,it emerges that:1)optimal pavement design involves complex mix optimization and there are theoretical and practical bases to set up a balanced approach to address the complexity of pavement design;2)high percentages of crumb rubber could optimise road acoustic response but this latter has a relationship with the tyre/road noise(expressed,for example,in terms of close proximity index)that calls for further investigation;3)aggregate gradation appears to be a reliable basis to predict surface texture and therefore,under given boundary conditions,tyre/road noise;and 4)further studies and investigations are needed in terms of local calibration of deterioration curves and setting up of a sound method to assess the frequency response of asphalt concretes and to govern on-site noise indicators based on mixture properties.

摘要： 一百多年的历史,是CARTIER卡地亚的Tank系列最引以为傲的资本,从历史中汲取些许灵感,便能够激扬出全新的闪耀火花,去年的Tank Must如是,今年的Tank Chinoise亦如是。自2015年以来,Cartier Privé系列每年均会对过往经典表款进行重新演绎,以限量的形式将卡地亚的造型腕表传承与现代美学理念浑然融合。继Crash、Tank Cintrée、Tonneau、Tank Asymétrique和Cloche de Cartier腕表之后,2022年,Tank Chinoise腕表揭开Cartier Privé系列的第六篇章。

摘要： Partial discharge(PD)signals are an important index to evaluate the operation state of intelligent substations.The correct distinction of PD pulse and interference pulse has become a challenging task.Because of the noise and the low signal-to-noise ratio,the stable signals become non-stationary.The selection of a wavelet basis,the selection rule of thresholdλand the design of the threshold function are the key factors affecting the final denoising effect.Therefore,an enhanced ant colony optimisition wavelet(ACOW)algorithm was applied to find the global optimal threshold through the continuous derivative threshold function and the ant colony optimisation(ACO)algo-rithm.At the same time the efficiency of adaptive search calculation,was also significantly improved.The method of the ACOW algorithm was compared with the soft wavelet method,gradient-based wavelet method and the genetic optimisation wavelet(GOW)method.Using these four methods to denoise four typical signals,different mean square errors(MSE),magnitude errors(ME)and time costs were obtained.Interestingly,the results show that the ACOW method can achieve the minimum MSE and has less time cost.It generates significantly smaller waveform distortion than the other three threshold estimation methods.In addition,the high efficiency and good quality of the output signals are beneficial to the diagnosis of local discharge signals in intelligent substations.

摘要： In this study,based on a closed bomb test combined with computational fluid dynamics,a structural finite element method,and an acoustic boundary element method,a fluid-solid acoustic one-way coupling calculation model is established for the combustion process of energetic materials in a closed bomb,and the effectiveness of the model is verified by experiments.It is found that the maximum peak sound pressure increases exponentially with an increase in loading doses or gas pressure.However,a change in the combustion coefficient of the energetic materials has little effect on the noise generated during the combustion process in the closed bomb.When the combustion coefficient is reduced by a multiple of 16,the maximum transient sound pressure is reduced by 1.79 dB,and the sound pressure level in the frequency band is reduced by 1.75 dB.With an increase in shell thickness,the combustion noise of the energetic materials in the closed bomb decreases,and the reduction range of the combustion noise increases with the increase in shell thickness.

摘要： This research is dedicated to the study of dynamics of vehicles moving through the additional entry lanes of a roundabout. Using the data created on the base of that model the constant coefficients of the sixth-degree polynomial function, previously proposed by us, have been found. In result of this there were obtained two analytic equations of vehicles’ movement, where one of them presented with the positive sign of the leading coefficient and the other one negative. These two equations allowed to make comprehensive investigation of the delays and the kinematics of the vehicles moving by such kinds of lanes. Based on the appropriate calculations it is determined vehicles’ consequent delays, velocities, accelerations and decelerations. Analyzing the delays, the dynamics of accelerations and decelerations, it is done an assumption that if the leading coefficient of algorithm of movement of vehicles is negative than it will lead to larger deceleration and consequently higher environmental pollutions and higher noises.

摘要： 本发明给出了一种基于Gaussian Noise CNN模型多变工况下轴承故障诊断方法与系统，包括使用振动传感器采集故障轴承振动信号，再对故障轴承振动信号采用定长随机分割方法进行分割获得数据样本；对数据样本按照滚动轴承的状态类型贴上各个类型对应的标签之后，再按照一定的比例划分为训练集、验证集和测试集；分别根据所述训练集和所述验证集中的数据制作出多种处于不平衡状态下的轴承故障数据集并将制作出的所有轴承故障数据集构成不平衡数据集；构建上述模型，分别用不同的轴承故障数据集训练上述模型，获得上述训练模型；利用上述训练模型对所述滚动轴承进行实时故障检测。本发明能够实时、准确、自动地识别轴承的运行状态，从而有效维护机械设备正常运转。

摘要： 本发明给出了一种基于Gaussian Noise CNN模型多变工况下轴承故障诊断方法与系统，包括使用振动传感器采集故障轴承振动信号，再对故障轴承振动信号采用定长随机分割方法进行分割获得数据样本；对数据样本按照滚动轴承的状态类型贴上各个类型对应的标签之后，再按照一定的比例划分为训练集、验证集和测试集；分别根据所述训练集和所述验证集中的数据制作出多种处于不平衡状态下的轴承故障数据集并将制作出的所有轴承故障数据集构成不平衡数据集；构建上述模型，分别用不同的轴承故障数据集训练上述模型，获得上述训练模型；利用上述训练模型对所述滚动轴承进行实时故障检测。本发明能够实时、准确、自动地识别轴承的运行状态，从而有效维护机械设备正常运转。

摘要： 本发明提供一种麦克风Noise、FFT、PSR性能测试系统及方法，所述测试系统调用AP仪器对麦克风Noise、FFT、PSR三种性能进行测试，测试系统包括：测试条件配置模块，用于配置测试麦克风Noise、FFT、PSR性能的测试条件；测试过程模块，用于根据测试条件配置模块配置的测试条件，调用AP仪器依次对麦克风Noise、FFT、PSR三种性能进行测试，对AP仪器测试的数据处理，并显示数据处理后的测试结果；测试结果模块，用于将测试过程模块获取的测试结果导出，并保存到对应的测试文件中。本发明能够解决目前测试结果准确性差、受人为影响因素大以及测试效率低下等问题。

摘要： 本发明涉及一种Poisson noise模型下对扩展目标成像时的相位恢复方法，将PD技术中的盲解算方法引入到PDPR技术中并结合PDPR对Poisson noise model的处理方式，提高扩展未知物体成像时的位相恢复精度，为将来我国更大口径望远镜光学系统在轨检测提供理论依据，以解决我国在大口径望远镜光学系统像差检测中遇到的困难，从而达到改善大口径望远镜光学系统成像性能的目的。本发明的相位恢复方法使扩展未知物体的位相恢复测量精度达到衍射极限水平。

摘要： 本发明提供了一种无pop noise高压D类音频功放系统及其上电启动时序，该功放系统包含：依次连接的积分器模块、比较器模块、逻辑控制电路、高压驱动电路模块、高压输出功率管模块和反馈电阻模块，该功放系统还包含预启动模块，所述积分器模块包含带失调自动校正功能的放大器。其优点是：采用预启动模块，使高压输出功率管模块关闭时和正常工作中高压输出功率管模块开启时的所有系统失配项保持一致；在此情况下，利用积分器模块进行失调自动校正，将上述失配项所带来的失调全部校正；校正功能完成后，再将输出功率管全部打开，使得最终的失调保持不变，即消除pop噪声。

摘要： 本发明涉及一种Poisson noise模型下对扩展目标成像时的相位恢复方法，将PD技术中的盲解算方法引入到PDPR技术中并结合PDPR对Poisson noise model的处理方式，提高扩展未知物体成像时的位相恢复精度，为将来我国更大口径望远镜光学系统在轨检测提供理论依据，以解决我国在大口径望远镜光学系统像差检测中遇到的困难，从而达到改善大口径望远镜光学系统成像性能的目的。本发明的相位恢复方法使扩展未知物体的位相恢复测量精度达到衍射极限水平。