Evaluation of Individual and Environmental Sound Pressure Level and Drawing Noise-Isosonic Maps Using Surfer V.14 and Noise at Work V.5.0

Noise pollution is one of the common physical harmful factors in many work environments.The current study aimed to assess personal and environmental sound pressure level and project the sound-Isosonic map in one of the Razavi Khorasan Paste manufacture using Surfer V.14 and Noise at work V.5.0.This cross-sectional,descrip-tive study is analytical that was conducted in 2018 in the Paste factory that contains Canister,production and Brewing unit.Following ISO 9612:2009,Casella Cel-320 was used to measure personal sound pressure level,while CEL-450 sound level meter(manufactured by Casella-Cel,the UK)was employed to assess environmental sound pressure level.Statistical analyzes was done using SPSS V.18 and Linear Regression test.The sound-isosonic maps were projected using Surfer V.14 and Noise at work V.5.0.The results of assessing personal sound pressure level indicated that the highest received dose(172.21%)and personal equivalent sound level(87.36 dBA)were recorded for workers in the Canister unit.According to results of measuring of the environmental sound pressure level,out of 16 measurement stations in this unit,overall 87.5%were regarded as danger and caution areas.The lowest and highest sound pressure levels in this units were 61 dBA and 92 dBA that belong to Brewing and Canister units respectively.Results indicate Over 75%of the Canister and production units had a sound pressure level greater than 85 dBA and these two units were regarded as the most dangerous area in terms of noise pollution.It is there-fore necessary to implement noise control measures,apply hearing protection program and auditory tests among workers in these units.

Measurement of Sound Pressure Levels in Anechoic Chamber and a Noisy Environment Experimentally

In real life, when a noise problem occurs, it is important to identify the cause and measure the noise of the source, since it may affect human beings or other constructions due to vibration generated from noise, so it is necessary to determine the noise related to a specific source like a machine in the presence of other sources which is a very important approach in noise control engineering. In this article a full experiment was executed to measure the sound pressure levels of various sources (stationary and non-stationary), in both an anechoic chamber and a non-ideal noisy environment. The sound pressure level was extracted for different sources and compared for both ideal and non-ideal environment. The results showed that acoustical free field of the space is the best field to do measurements to avoid reflection, on the other hand the difference between the source and the background should be more than 3 dB to get better results.

Presenting a Signal to Noise Ratio Model Based on the Combined Effect ofSound Pressure Level/frequency, Exposure Time and Oral Potassium:Experimental Study in Rats

Exposure to noise can lead to anatomical,nonauditory,and auditory impacts.The auditory influence of noise exposure is manifested in the form of Noise-induced hearing loss(NIHL).The current study aimed at present a signal to noise ratio model of otoacoustic emission of rats’ears in the light of the combined effect of sound pressure level,sound frequency,exposure time,and potassium concentration of the used water.In total,36 adult male rates,whose age varied from 3 to 4 months and had a weight of 200±50 g,were randomly divided into 12 groups,with each group consisting of 3 rats.The rats in both groups(case and control groups)were exposed to SPLs of 85,95,and 105 dB,emitted from sources that generated white noise.A distortion product otoacoustic emission(DPOAE)machine(4000 I/O manufactured by Homoth of Germany)was utilized to gauge the signal to noise ratio(SNR)of otoacoustic emissions of rats’ears at various frequencies in an acoustic room.The inclusion criterion was SNR≥6 dB.The collected data were fed into the Statistical Package for Social Sciences(SPSS)version 18,followed by conducting descriptive and inferential data analysis procedures.The results of SNR analysis indicated that over 82%of all data had SNRs that were equal to or greater than 6 dB.These data were considered as acceptable response.Furthermore,SPL and sound frequency had significant associations with SNR(P<0.0001).Exposure time also significantly correlated with SNR(P=0.008).However,the potassium concentration of the used water had no significant correlation with SNR(P=0.97).High sound pressure levels result in lower DPOAE.Furthermore,higher frequency leads to higher SNR.On the contrary,longer exposure time reduces SNR.Finally,the potassium concentration of the used water has no effect on SNR.

Evaluation of Environmental Sound Pressure Level,Drawing of Noise-Isosonic Map Using Surfer V.19,and Prioritization of Engineering Noise Control Methods Using the Analytic Hierarchy Process(AHP):A Field Study in CGS Stations

Noise pollution is one of the most significant harmful physical factors in the industrial and occupational environments.Due to the high costs of exposure to excessive noise;continuous sound evaluation,propose and implement noise control plans in occupational environments is necessary.Thus,the present study aimed to review environmental sound measurements,drawing of noise maps,and prioritizing the engineering noise control methods using the Analytic Hierarchy Process(AHP).This study was a descriptive-analytical study that aimed to assess occupational noises and present a control plan in the City Gas Stations(CGSs)of Kerman,Iran in 2021.The present study was done in two phases.In the first phase,six CGSs were investigated to measure and evaluate the noise.In addition,the noise map of a CGS was drawn using the Surfer software.Finally,the AHP was used in the second phase of the research to prioritize the control measures.In this phase,four criteria and ten alternatives were identified.According to first phase results,the sound pressure level(SPL)of the stations varied from 76 to 98 dBA.Besides,the majority of the studied stations had a sound level higher than 85 dBA(danger zone).The second phase of the study showed that out of the four evaluated criteria,the executability criterion had the highest impact and the cost criterion had the lowest impact on the selection of control measures with a weight of 0.587 and 0.052,respectively.Based on the results of prioritization of the alternatives,using a silenced regulator(weight of 0.223)and increasing the thickness of the tube(weight of 0.023)had the highest and lowest priorities among the alternatives,respectively.The use of engineering noise control methods such as using silenced regulators was the best way to control the noises of CGSs.Additionally;it is noteworthy that AHP is a practical method for prioritizing alternatives to achieve the most accurate decision-making.The results of AHP can be of great help to health and safety experts and managers in choosing the sound engineering control measures more precisely.

Comparison of the Sound Power Levels of an Aerodynamically Designed EGV and a State-of-the-Art EGV

Within previous EU projects, possible modifications to the engine components have been investigated, that would allow for an optimised aerodynamic or acoustic design of the EGV （exit guide vanes） of the TEC （turbine exit casing）. However, the engine weight should not be increased and the aerodynamic performance must be at least the same. This paper compares the sound power level of a state-of-the-art TEC （reference TEC） with typical EGVs with an aerodynamically optimised TEC configuration for the engine operating point approach. It is shown that a significant weight reduction （only bladings considered） and reduction in engine length can be achieved but the sound power level for the fundamental tone （lst blade passing frequency） for this acoustically important operating point is increased. It is also shown that the losses of the aerodynamical optimised EGVs are higher for this off design point but significantly lower at the aero design point. Measurements were conducted in the STTF （subsonic test turbine facility） at the Institute for Thermal Turbo machinery and Machine Dynamics, Graz University of Technology. The inlet guide vanes, the LPT （low pressure turbine） stage, and the EGVs have been designed by MTU Aero Engines.

Environmental Sound Recognition Using Double-Level Energy Detection

The performance of classic Mel-frequency cepstral coefficients (MFCC) is unsatisfactory in noisy environment with different sound sources from nature. In this paper, a classification approach of the ecological environmental sounds using the double-level energy detection (DED) was presented. The DED was used to detect the existence of the sound signals under noise conditions. In addition, MFCC features from the frames which were detected the presence of the sound signals by DED were extracted. Experimental results show that the proposed technology has better noise immunity than classic MFCC, and also outperforms time-domain energy detection (TED) and frequency-domain energy detection (FED) respectively.

400 km/h高速铁路直立式声屏障降噪效果及安全性研究

开展400 km/h高速铁路噪声影响研究是践行“交通强国”战略的有力举措。为研究400 km/h高速铁路噪声特性及辐射源强,获取现有直立式声屏障在速度400 km/h条件下降噪效果及适应性,采用有限元模型进行仿真计算,模拟计算400 km/h高速铁路噪声源强并进行组成分析,对高速铁路通用的直立式声屏障降噪效果、耐久性、安全性等进行分析研究,对目前直立式声屏障适应性提出实施建议。研究表明:高速列车以速度400 km/h运行时,距离铁路外轨中心线25 m、轨上3.5 m处,桥梁段总声级为97.8 dB(A),路基段总声级为96.7 dB(A),气动噪声大于轮轨噪声;提出现有直立式声屏障在速度400 km/h条件下插入损失为2.7~8.9 dB(A);在安全方面,提出立柱底部螺栓养护年限;针对目前铁路直立式声屏障通用图适用性进行分析,提出结构安全优化建议。研究结果可指导400 km/h高速铁路噪声影响分析及直立式声屏障设计工作。

无人机系列化旋翼气动噪声特性对比研究

旋翼的气动噪声是各类旋翼无人机噪声的主要来源,为降低无人机整体噪声和提升其声隐身性能,文中针对某无人机的系列化等径旋翼开展定转速气动噪声特性的对比研究.分别建立各旋翼气动噪声特性预测大涡模拟计算模型,将获取的各旋翼表面压力脉动信息作为声学求解输入,基于FW-H方程计算了等距(3R)和不同方位的旋翼远场噪声特性并进行了试验验证,5个型号旋翼等距处总声压级仿真与试验结果误差不大于4.3%,气动噪声呈现明显的偶极子特性,气动噪声径向声压级明显高于轴向值,且不同旋翼的气动噪声声压级与旋翼转矩具有正相关关系,与旋翼升力间关系则不明显.

带式输送机托辊组振动噪声仿真分析及参数优化

带式输送机托辊组产生的振动噪声受多因素联合影响,为解决其振动噪声过大问题,文章提出一种基于有限元-边界元理论对托辊组振动噪声分析与优化的方法。首先,对托辊组进行模态分析与动力学仿真,探明托辊组的振动特性;然后,基于有限元-边界元复合声场仿真方法,作声场的谐响应分析计算托辊组的声场分布,并搭建实际测试平台验证声学仿真模型的可靠性;最后,结合输送能力与轻量化约束条件,得到托辊组结构参数与工作参数的最优解。结果表明,有限元-边界元法可有效模拟托辊组声场分布和变化规律,优化后托辊组噪声声压级较优化前减小约6.1dB,并且托辊组综合性能均有所改善,可对实际工程中的带式输送机优化设计起到有效的指导作用。

基于改进DBNet-RNN的声级计读数识别方法

为提高声级计校准工作效率,提出了一种基于深度学习神经网络的声级计图像读数检测与识别方法。读数检测模型以DBNet为基础模型,将ShuffleNetV2作为主干网络,显著降低模型参数量;为提高读数区域检测精度,引入高效通道注意力ECA模块,提高网络对于通道特征的提取能力,优化后的模型在保持精度的同时参数量缩减为原来的15.4%,计算量缩减为原来的67.4%。读数识别模型以CRNN为基础模型,先加入批量规范化层,提高网络训练时的稳定性;然后,引入残差块替换原有的卷积块,提高了网络对于复杂特征的提取能力;将Dropout应用于网络中,提高网络的泛化能力;此外,在合成读数数据集上对读数识别模型进行预训练,有效增加了模型准确率。改进后的方法准确率达到了99.7%,相较原方法提高了2.4%。实验结果表明,该方法对声级计图像中存在的字体多样、光照不均、模糊等影响因素具有较强的鲁棒能力,对声级计图像中的读数具有较高的识别精度。

水下等离子体声源放电特性和声特性实测与分析

在小型消声水池中,同步测量水下等离子体脉冲声源的放电特性和声特性,实验分析研究了其在单电极和多电极下负载注入峰值功率和放电能量对声特性的影响。结果表明,在相同的电极数和间距下,直达波脉冲声源级仅与负载注入峰值功率有关,气泡脉冲声源级和气泡周期则主要受放电能量影响,多电极放电通过减小单根电极放的电能量来减小气泡脉冲声源级和气泡周期。此外,在相同的充电电压下,减小充电电容对电极数的比,可以增大直达波脉冲声源级并压制气泡脉冲;负载注入峰值功率对放电能量的比对声特性的影响也呈现出类似规律。实测及其分析结果可为进一步优化水下等离子体脉冲声源的声特性提供参考。

老旧小区声环境评价及优化策略研究

老旧小区内部建设年代较早,声环境形势面临一些挑战和问题。基于此,以吉林省长春市为例,选取4个不同建筑布局形式的老旧小区为研究对象,根据小区的不同范围设置多个监测点,同时对居民进行访谈和问卷调查,对小区主要噪声源进行分析。基于噪声问题和居民对于不同声源的偏好性,提出长春市老旧小区室外声环境优化策略,以提高居民生活质量。

树脂基复合材料摩擦噪声特性研究

树脂基复合材料被广泛应用于多种制动系统中,但其在摩擦过程中易产生严重的环境噪声污染.通过摩擦试验和有限元模拟方法,总结了不同试验条件下摩擦系数、摩擦力波动系数以及摩擦噪声有效声压级的变化规律,分析了摩擦噪声与摩擦界面稳定性之间的关系,揭示了酚醛树脂基复合材料摩擦噪声的产生机理,同时研究了温度对其摩擦学性能及摩擦噪声行为的影响.结果表明:摩擦系数和摩擦力波动系数随载荷、相对滑动速度以及温度的改变呈现出不同的变化趋势,摩擦噪声的有效声压级与摩擦力波动系数正相关,且噪声的自功率谱与摩擦界面振动自功率谱相吻合.摩擦噪声的产生归因于接触界面的不稳定振动,研究结果为树脂基复合材料摩擦噪声的控制及发生机理提供了一定的理论基础.

艇后大侧斜螺旋桨非定常空化及噪声性能研究

结合数值和试验方法,对艇后七叶大侧斜螺旋桨进行空化性能及空化噪声分析.采用雷诺平均(RANS)方法和Ffows Williams-Hawkings声学类比方程混合的计算方法,结合SST k-ω湍流模型和Schnerr-Sauer空化模型,研究了艇后七叶螺旋桨的非定常空化脉动压力、推力系数、速度分布及空化形态演变过程,并将数值结果与试验结果进行比较验证.基于艇后螺旋桨空化噪声的数值仿真,分析不同空化数下各阶压力脉动幅值、噪声功率谱、频率普.结果表明:随着空化数的减小,脉动压力波动峰值减小,桨叶无明显空化时,噪声高幅值主要集中在低频段,空化发生时,高频段噪声的声压级会明显增大,声功率级增大60 dB,而低频段的噪声随着空化的发展而增加,空化完全发展时,所有频段噪声一起增大到更高水平.

变压器声级试验标准差异性对比分析

本文作者对三个变压器声级试验标准(GB/T 1094.10、IEEE C57.12.90-2015和IEC 60076.10-2016)之间的差异性做了对比分析,指出了其中诸如修正因数、测量点数、数据计算等多方面的不同。

超声消除电缆火灾烟雾的实验研究

声波团聚技术是利用高强声场的作用使颗粒物发生相对运动从而碰撞并凝聚,大幅减少悬浮的颗粒物。当今城市地下电缆一旦发生火灾将造成巨大的生命及财产损失。在火场应用声波团聚技术能够大幅提高火场的能见度,有助于人员逃生。文章研究了超声场下消除地下电缆火灾烟雾的效果。首先设计了一款频率为18 kHz的气介式换能器,并对其进行模态分析;随后加工了声源,测试其发声效果。结果表明,换能器在开放空间及团聚室内声压级最高分别可达154.1 dB及158.7 dB。开放空间下输入功率越高、越靠近圆盘中心,声压级越高;团聚室内中间监测点处由于壁面及底部反射作用声压级最高。团聚实验结果表明,在声压级为155 dB、初始透光率为8%时,对于液相烟雾及电缆烟雾,分别在5、15 s内透光率达到60%,这表明在超声场下,团聚效果显著,且团聚效果随声压级的增大而增大。

气井环空液面下泄漏声场模拟

气井油套管环空液面下泄漏声波的产生及传播机理一直备受关注。为研究液面下泄漏声波声源特性,建立了井下油套管环空泄漏物理模型,联合STAR-CCM+软件对环空液面下气体泄漏状态进行了流场及声场的仿真分析,得到了泄漏流场的压力和相态云图及不同泄漏孔径、泄漏位置和泄漏速度下的声压频率曲线。研究结果表明:随着泄漏速度升高,泄漏气流冲击管壁且液面震荡剧烈,液面下泄漏声源主要以四极子声源为主;液面上泄漏声源主要由液面震荡破裂及液面下四极子声源共同产生,泄漏声波能量的主要频率分布在0~100 Hz区间;在单一变量条件下,泄漏声压级随泄漏孔径、泄漏速度及泄漏位置距底部距离的增大而增大。研究结果可为在井口应用声波法检测液面下泄漏奠定理论基础。

提高煤层气直井动液面解释精度方法研究与应用

煤层气井动液面解释精度对于煤层气井精细化排采管控至关重要,本文对比了接箍法、音标法及声速法等测液面方法的优缺点,分析了影响动液面解释精度的主控因素为井筒温度和气泡段,从而提出了一种提高动液面解释精度的新方法。此方法综合考虑了影响动液面解释精度的各个要素,能够依据所解释液面较为准确地反映煤层气井的井底流压,克服了前期其它方法所存在的一系列问题,为煤层气井精细化排采管控提供保障。

基于HyperMesh的乘用车驾驶室NVH性能分析

为测定某乘用车驾驶室噪声、振动、声振粗糙度(noise vibration harshness,NVH)性能,采用有限元软件ANSA建立车辆内饰车身模型,HyperMesh建立驾驶室声腔模型,并采用HyperMesh将车身模型与声腔模型耦合连接,进行声腔模态分析和噪声传递函数分析。声腔模态分析结果表明:驾驶室声腔模型各阶次声压分布基本处于对称状态,符合车内声压分布规律,声腔模态结构合理。噪声传递函数分析结果表明:在不同方向、不同位置的激励作用下,驾驶员右耳处最大声压级为55.60 dB,未超出57 dB的限值规定;后排乘客右耳处最大声压级为56.25 dB,未超出58 dB的限值规定,车辆驾驶室满足NVH性能要求。

基于通道和帧级特征注意力模型的环境声音识别

为了对环境声音进行更好的识别,提出基于通道和帧级特征注意力的环境声音识别卷积神经网络模型。该模型针对声音特征特点选取一维卷积以提高模型对声音特征信息的提取能力,并引入SE-Res2Net模块实现对声音特征细粒度上的全局感受并帮助模型关注特征通道间的信息,在全连接层前加入注意力统计池化模块,增强模型对表征不同声音类别的关键帧级特征的学习以提高模型识别性能。采用Urbansound8K数据集,实验结果表明:所提模型在测试集上的训练准确率达到94.5%,即模型可以有效学习声音特征中表征不同环境声音的关键信息并进行正确预测。对消融实验结果分析可得,所提模型的设计可使其分类错误率的下降率达到43.8%,表明模型对一维卷积的应用和各个模块的引入是有效的,可见所提环境声音识别模型性能优越。