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.

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.

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.

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.

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。

声校准器声压级计量比对研究

声校准器是空气声声压量值传递的主要标准器之一,既作为声学计量标准中的标准器,又作为计量器具广泛应用。为考察国内实验室声校准器声压级测量量值准确一致程度,考核声校准器计量标准、环境条件、人员水平、方法、数据处理、管理能力等方面的实际水平和能力,国家市场监督管理总局组织了声校准器声压级量值计量比对,中国测试技术研究院作为主导实验室,参比实验室包括主导实验室在内的6家国内计量技术机构。文章介绍了声校准器声压级的测量原理与比对实施过程,应用归一化偏差对测量数据进行处理,分析了比对数据与结果,验证了参比实验室的比对结果具有较好的一致性,针对一些技术问题提出了建议与解决方法。

Active control of structural sound radiation in an acoustic enclosure consisting of flexible structure

The active control of structural sound radiation in an acoustic enclosure is studied by using distributed point force actuators as the secondary control force, and the control mechanisms for the radiated noise in the cavity are analyzed. A rectangular enclosure involving two simply supported flexible plates is created for this investigation. The characteristics of the primary and secondary sound field and the structural-acoustic coupled system are analyzed, and the optimal control objective for reducing the sound pressure level （SPL） in the cavity is derived. The response of the SPL in the cavity is analyzed and compared when the secondary point force actuators with different locations and parameters are applied to the two flexible plates. The results indicate that the noise in the cavity can be better controlled when some point force actuators are applied to two flexible plates for cooperative control rather than the point force actuators being only applied to the excited flexible plate.

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。

应急广播系统对声环境影响和优化措施

随着浙江省新一轮应急广播系统的建设,应急广播终端的部署密度显著提升。这一趋势下,应急广播对当地声环境的影响成为了系统设计与建设过程中一个不可忽视的问题。本研究依据国家现行的噪声控制标准,深入分析了影响广播声音传播的各种因素,并针对不同的应用场景推荐了适宜的声压级水平。此外,本文还提出了一系列优化措施,旨在有效平衡应急信息传达的有效性与居民生活环境质量之间的关系。

大型客车座舱语言清晰度试验研究

大型客车座舱语言清晰度对乘坐体验及驾驶安全具有重要影响。以48座柴油营运客车为例,结合座舱内声压级、混响时间、座舱内外空气隔声量等客观声学参量,将客观评价融入主观研究中。构建量化评价模型,连续采集静止和恒定车速运行的噪声数据,揭示多种复杂激励源共同作用下的大型客车座舱内真实声环境。分析听音者位置、发音者性别及运行工况对语言清晰度的影响,避免因语言清晰度造成的信息误解、误判。结果表明:不同区域的噪声幅值差别较大,语言清晰度随距发音者位置的增大而减小,呈现非正态分布;乘客区后部座舱声环境最差,且为语言清晰度分析阈值边界值,乘客区前部与中部的声环境较好且无显著差异;由于时长、基音及能量多方面的不同,使用女发音者优于男发音者,女发音者的语言清晰度效果较好且更稳定;在相同性别发音者的情况下,语言清晰度与运行速度呈现负相关,当车速达到60 km/h时,整体数据波动较大,语言清晰度数据波动达到峰值,平均得分降至74.6。本研究对降低大型客车座舱内噪声干扰、改善座舱内声环境提供积极的指导意义,适用于大型客车内声环境的优化设计。

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.

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.

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。

基于GA-BP神经网络模型的石墨烯发声器研究

为了解决传统石墨烯发声器物理模型计算量大、精度不高的问题,提出了一种基于GA遗传算法的BP神经网络模型,该算法模型具有更高的精度和适应性。首先,介绍了石墨烯热声发声原理以及实验设计,建立了GA-BP神经网络模型。其次,对模型的参数进行了调节,并对比了基于dropout、基于正则化、基于正则化和GA遗传算法的三种神经网络模型。随后在模型中输入石墨烯发声器的正弦激励幅值、频率以及测量距离,使用GA遗传算法对隐藏层的权值和偏置进行全局寻优,将寻优结果代入BP神经网络,最终预测出给定条件下的声压级。结果表明,在均使用正则化的条件下,BP神经网络预测准确度为98.05%,均方差为0.23;GA-BP神经网络预测准确度达到98.62%,均方差仅为0.14。优化后精准度提高了0.57%,均方差降低了41.36%,展现出更加优异的准确性和适应性。该研究为预测多类特征传感器的非线性输出结果提供了一种高精准度、高适应性的方案。

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。

400 km/h高速列车车下带格栅裙板区域气动噪声机理及影响因素分析

位于高速列车车体下部区域的通风口格栅与设备舱壁面构成格栅–空腔结构,列车高速运行时,该结构的流声耦合问题较为突出,有必要深入分析其流声耦合机理。将位于车体下部区域的带格栅裙板简化为带格栅的二维空腔模型(格栅–空腔结构),采用延迟分离涡数值模型(Delayed Detached Eddy Simulation,DDES)研究其气动噪声产生机理、流场和声场特性等。研究结果表明:当列车以400 km/h速度运行时,格栅–空腔结构开口处的剪切振荡较为剧烈,特别是空腔冲击边缘附近区域;基于总声压级的空间、频域分布和湍流压力波数–频率谱,发现形格栅–空腔结构的流场始终处于自激振荡的过渡状态,且各位置的总声压级和波数域上的振荡幅值始终低于V形格栅–空腔结构和半圆环形格栅–空腔结构;对目前常用的半圆环形带格栅裙板考虑通风口的出风作用后,观察到空腔内部的涡团演化明显减缓,直接导致格栅附近的总声压级大幅下降约15 d B,表明出风作用能够显著降低带裙板格栅的近场噪声。

机器噪声平均声压级计算方法差异性实证研究

针对家用电器、电动工具、电弧焊机、容积式压缩机、水泵、风机等机器的噪声平均声压级计算过程,介绍典型的机器噪声平均声压级计算方法。分析多种计算方法的差异,同时给出确定噪声平均声压级推荐采用的计算方法。

声波干预下微液滴群微物理变化及其与雷达反射率因子关系研究

通过室内实验,探究了声波干预下微液滴群微物理变化特征,建立了滴群特征粒径与雷达反射率因子之间的关系,讨论了粒径增量与宏观雨强增量之间的量化关系。结果表明:(1)存在优选声波频率和临界声压级,实验重点关注的120 Hz声波频率(超过临界声压级)干预实验滴群,引起微液滴群特征粒径增大、粒径谱右移变宽,粒子数浓度减小,雷达反射率因子增大,该结论对于30~280 Hz声波同样适用。(2)D90-Z相关系数在0.9以上,大粒径对雷达反射率因子贡献较大,拟合参数a、b范围分别为[2.84×10^(-8),1.104]和[0.6713,9.2000]。(3)滴群特征粒径增量与宏观雨强增量呈线性正相关关系,相关系数均在0.98以上,并且声压级越大,拟合的线性斜率越小。研究结果对外场试验效果评价具有重要的参考意义和指导价值。