An examination of the effects of various noises on physiological sensibility responses by using human EEG

This study investigated human stress levels based on electroencephalogram (EEG) data and carried out a subjective evaluation analysis about noise. Visual information is very important for finding human’s emotional state. And relatively more previous works have been done than those using auditory stimulus. Since there are fewer previous works, we thought that using auditory stimulus is good choice for our study. Twelve human subjects were exposed to classic piano, ocean wave, army alarm, ambulance, and mosquito noises. We used two groups of comfortable and uncomfortable noises are to see the difference between the definitely different two groups to confirm usefulness of using this setting of experiment. EEG data were collected during the experimental session. The subjects were tested in a soundproof chamber and asked to minimize blinking, head movement, and swallowing during the experiment. The total time of the noise experiment included the time of the relaxation phase, during which the subjects relaxed in silence for 10 minutes. The relaxation phase was followed by a 20 — second noise exposure. The alpha band activities of the subjects were significantly decreased for the ambulance and mosquito noises, as it compared to the classic piano and ocean wave noises. The alpha band activities of the subjects decreased by 12.8 ± 2.3% for the ocean wave noise, decreased by 32.0 ± 5.4% for the army alarm noise, decreased by 34.5 ± 6.7% for the ambulance noise and decreased by 58.3 ± 9.1% for the mosquito noise compared to that of classic piano. On the other hand, their beta band activities were significantly increased for the ambulance and mosquito noises as it compared to classic piano and ocean wave. The beta band activities of the subjects increased by 7.9 ± 1.7% for the ocean wave noise, increased by 20.6 ± 5.3% for the army alarm noise, increased by 48.0 ± 7.5% for the ambulance noise and increased by 61.9 ± 11.2% for the mosquito noise, as it is compared to classic piano. The results of the subjective evaluation were similar to those of the EEG signal analysis. The results from this study may contribute to apply this method to actual products which are closely related to human-machine-interface (HMI) like air-conditioner, car, and so on. So, our experiment was designed for its own purpose.     

复合结构泡沫铝隔声性能的研究

采用自制的试验装置对泡沫铝与实体铝复合结构的隔声性能作了研究。结果表明：泡沫铝与实体铝的复合结构在声频范围内均具有较好的隔声作用且对频率敏感，在500-1000Hz内隔声效果最佳，综合降噪率为40％；隔声效果受两者复合方式的影响不大，但随泡沫铝孔结构的不同而异；孔径为1．0mm、孔隙率为60％的泡沫铝试样，隔声效果最优，可在实体铝隔声的基础上再降噪16％-23％。     

Transmission loss of a silencer using resonator arrays at high sound pressure level

Helmholtz resonator is generally used to reduce the low frequency noise. However, it has only high transmission loss in a narrow band at the resonance frequency. In order to obtain broad band transmission loss, studies of a silencer using various resonator arrays have been carried out. These previous studies have been limited to low incident sound pressure level conditions with no change of impedance with respect to pressure. In the case of high sound pressure, the resistance increases due to nonlinear behavior at the neck of a resonator. As a result, the desired noise reduction performance cannot be achieved due to the transmission loss decrease. To predict the transmission loss of a silencer using resonator arrays at high sound pressure level, impedance variation depending on the incident sound pressure level should be considered. Furthermore, resonator’s numbers and order of arrangement are significant design parameters for design of transmission loss shape.     

基于阵列测量与声功率分析的三轮摩托车整车噪声源识别

针对某型三轮摩托车加速行驶噪声超过国家标准限值,基于声波声压、阶次分析等理论,运用频谱分析、阵列声压测量以及声功率分析,对车辆主要噪声源进行了识别,确定排气系统为主要噪声源,排气消声器辐射噪声在中、低频和高频段贡献相当,将吸声材料运用到摩托车覆盖件上,进一步验证了排气消声器为主要噪声源,并取得了一定的降噪效果。     

轴系扭振诱发的车内异响诊断及优化

针对某涡轮增压轿车在加速过程中出现320~470Hz异响问题进行诊断与优化。首先,对异响特性及源头进行诊断,按照一般整车异响诊断流程,依次进行了基本的声振测试、机舱内声强测试以及燃烧测试,发现异响源自发动机且为整体扩散式异响,排除了燃烧激励起异响的可能性之后,判断异响由轴系振动引起;然后,进行小惯量扭振减振器(torsional vibration damping,简称TVD)的轴系扭振测试来验证异响与扭振的关系,时频图上显示异响频段内扭角特性与异响十分相似,断定异响源自轴系扭振;最后,针对装配大惯量TVD条件下的轴系进行扭振仿真计算,350Hz对一阶扭转模态具有最优的减振效果。依照仿真结果重新设计TVD进行试验,结果显示车内噪声异响频段内幅值衰减明显,主观评价"咕噜"音消失。本研究对于主流轿车的车内异响诊断和优化都具有着重要的指导意义。     

动力调谐陀螺再平衡回路数字化的研究与实现

为克服模拟再平衡回路时由控制补偿和温度补偿引起的各种问题,研究了动力调谐陀螺仪再平衡回路的数字化设计和实现方法。采用基于DSP的SVPWM数字化方法设计了频率可调的高精度三相逆变电源,解决了传统陀螺电机电源频率调整困难、相位稳定性低、效率低等问题;基于dSPACE半实物仿真系统设计了双输入双输出频率特性分析仪,辨识出数字再平衡回路的开环离散传递函数矩阵;利用矩阵求逆法与经典控制器设计方法设计了数字解耦合校正环节,使陀螺系统能够获得更好的动态性能。实验结果表明:所设计的陀螺电机电源频率稳定性优于±1.5×10^－6,波形失真度＜5%,满足陀螺使用要求;控制后的锁定回路带宽＞70Hz,阶跃响应超调量＜5%,上升时间＜5ms,输入信号频率为10Hz时,两轴交叉耦合＜1%。在保证稳定裕度的前提下,实现了比模拟再平衡回路更好的系统动态性能,为深入研究现代控制方法在动调陀螺再平衡回路中的应用奠定了基础。     

柴油机噪声测试与分析系统的开发及应用

基于近场声全息(NAH)技术及空间快速傅里叶变换(FFT)算法,利用虚拟仪器软件Labview开发了柴油机噪声测试与分析系统;对系统中的数据采集模块、NAH模块、仿真程式模块进行了分析;通过已知声源进行仿真模型校正,该系统具有对噪声进行频域分析及识别的功能.该文以直列四缸涡轮增压柴油机为测试对象,在次推力侧主要对180...     

汽车门密封处的气动噪声研究

使用数值模拟方法对汽车门密封处的气动噪声进行了模拟,在得到流场的基础上,应用FW-H声学类比方程分析了由流动诱发的气动噪声.通过数值模拟观察到了涡结构的脱体及门密封处腔体内部的自激振荡过程,并针对其中一个自激振荡循环做了说明与分析.得出了由流动诱发噪声的声压-频率曲线,发现采用流速30m/s时,汽车门密封处流动噪声声压级在70db以下;频率在2000Hz以内的峰值为349Hz及其高次谐波噪声,2000Hz以上出现了非349.65Hz倍频的峰值,体现了伴流模式诱发声场的复杂性.     

P91钢蠕变损伤的非线性超声检测方法研究

针对现有的非线性超声评价金属高温蠕变状态的方法中存在的问题,借鉴了高频段能量与低频段能量之比作为非线性参数的定义方式及兰姆波应力波损伤因子表达式,提出利用一定频带范围内非线性参数的累积效应表征金属蠕变损伤程度的新方法。根据非线性能量从低频向高频转移的特性,得到某一激发频率下的高频段能量与低频段能量之比的非线性参量,其次,在考虑基波能量与高次谐波能量随频率变化的基础上,对一定频率范围内得到的非线性参量进行积分,得到累积非线性响应总和。应用该方法对实际现场截取的P91钢主蒸汽管道蠕变程度进行检测（该管道运行温度为550℃,运行压力为3 MPa,运行时间约3万小时）。检测结果与较精确的X射线衍射法测得的残余应力及传统的非线性系数方法作对比,结果表明,累积的非线性参数方法灵敏度较高,稳定性较好,与应力的测量结果符合性较好,能够跟随试样所受应力的改变评价管道的蠕变程度。     

磨机负荷的磨音多频带检测研究与开发

对磨音的频谱分析。发现与磨机负荷相关的磨音频带范围比较大,从500Hz到4kHz左右。在此基础上本文设计多组带通滤波器将磨音信号的频域划分多个频带。对磨机的各个状态（空磨、正常、饱磨）在不同的频带内检测,经相关软件分析处理,确定磨机的工作状态以及磨机的负荷量。     

基于独立分量分析的脑电信号消噪

脑电信号中往往含有各种形式的噪声干扰信号。这些干扰成分包括眼电、心电伪迹以及工频干扰等。由于干扰信号和脑电信号在频域上相互重叠,因此用时域或频域滤波的方法难以有效地消除脑电信号中的干扰成分。独立分量分析(Independent Component Analysis,ICA)是20世纪90年代发展起来的一种新的盲源分离方法(Blind Source Separation,BSS),将ICA方法应用于实测脑电信号的处理,获得非常理想的消噪效果。     

A digital computing synthesizer with a V-shaped frequency change law

The structure of a digital synthesizer based on direct digital frequency synthesis is described. The synthesizer can operate in the frequency band of 0–10 MHz with a frequency step of <0.005 Hz, the phase noise level is less than ?140 dB/Hz, and the amplitude noise level is less than ?60 dB/V.     

一种耳鸣治疗声优化算法的研究

为解决传统耳鸣治疗声难以兼顾治疗效果和音频悦耳程度等问题,本文提出了一种兼顾音频悦耳程度和耳鸣治疗效果的创新音频处理算法。首先遵循耳蜗感音的对数分布特性,基于固定上下限截止频率的数字滤波器组对原始自然声的音频进行分频滤波;然后对原始自然声的音频沿着频率对数轴均衡,使得声频在全频率范围内实现能量均衡的同时,兼顾治疗效果。结果显示,经过对数能量均衡处理后的音频,不但整体符合粉红噪声的分布,且在4 001～8 000 Hz和8 001～10 000 Hz高频段内的能量得到显著提高,处理后的音频能量分别超过原始音频能量15倍和100倍。本文提出的创新算法不但满足耳鸣患耳对音频感音的悦耳习惯,而且为高频耳鸣无疗效的国际难题提供了治疗方案。     

汽车声品质的GA-BP网络预测与权重分析

为了高效而准确地评价与控制车内噪声品质,以B级车稳态工况下副驾位置的车内噪声为研究对象,采用等级评分法对采集到的声音样本进行了主观评价试验,同时计算了7个客观参数。以客观参量为输入,声品质主观结果为输出,引入基于遗传算法的BP神经网络建立了声品质预测模型。实验显示该模型输出结果与实际评分的相关系数达到0.928,检验组的预测最大误差为±8%。以所建模型的连接权值,分析了客观参数对主观评价结果的贡献度,并以影响系数较大的参数为输入重新构建了预测模型。研究结果表明：稳态工况下,车内声品质主要受响度、粗糙度和尖锐度的影响,其预测模型可由这3个参数来描述。     

多带隙联合的声子晶体滤波梁弹性波传播特性

提出了一种包含Bragg散射、整体局域共振和局部局域共振机理的多带隙联合声子晶体滤波梁,通过传递矩阵法与Bloch定理求得无限周期结构各阶带隙为0～170 Hz、180～262.6 Hz、552.3～597 Hz、974～1 563 Hz、1 903～2 667 Hz;并调节结构参数,得出带隙调制规律和带隙机理。同时,与其他3种工况声子晶体梁带隙特征进行对比分析,证明了声子晶体滤波梁在带隙宽度、丰富度以及弹性波衰减率方面均有着相对优势,具备更好的过滤或抑制结构中弹性波的性能。此外,求解近声子晶体滤波梁的振动传递系数,得出在各阶带隙范围内,弹性波的传播存在明显衰减,验证了带隙的存在。最后为探究弹性波在带隙/通带范围内的波动模式,分别提取位于带隙/通带范围梁体位移分布,发现在带隙频率范围内的弹性波沿波动方向快速衰减,表现出带隙特性;通带频率范围内的弹性波无明显变化或衰减,表现出通带特性。     

钹型开槽式阀压电泵的设计

由于有阀压电泵内部阀体所受应力过大易导致阀体失效,本文提出了钹型开槽式截止阀来减小有阀压电泵内部阀体所受应力。基于钹型开槽式截止阀设计了有阀压电泵,分析了钹型开槽式阀压电泵的工作原理。对钹型开槽膜片进行了受力分析,研究了该压电泵的输出性能及耦合作用下的膜片应力。加工制作了钹型开槽式阀压电泵样机,建立了钹型开槽式阀压电泵的有限元模型,数值计算了流固耦合作用下的阀体应力值。计算结果表明:在压电泵正常输出的驱动频率范围内,当驱动频率为418Hz时,膜片所受应力的计算值也达到最大,为81.74 MPa。最后,进行了压电泵性能试验。试验结果显示:该压电泵的输出流量最大值和振子振幅最大值均出现在低频段;当驱动电压为160V,驱动频率为5Hz时,输出流量达到最大,为6.6g/min;驱动频率为4Hz时,压电振子振幅达到最大,为165.8μm。文中的研究验证了钹型开槽式阀体压电泵的有效性,并得出当钹型开槽式阀压电泵工作在低频段时,阀门所受应力远小于高频段时阀门的应力值。     

活塞式压缩机振动测试研究

为了降低压缩机整机的振动烈度和加速度值,找到一种最佳的减振器。针对某型压缩机,在试验现场,进行了振动和噪声测试。分别选取BE-85,BE-160,BE-300等3种型号的橡胶减振器进行测试,测点取在了联接螺栓正上方。通过观察和比较压缩机振动指标,换上减振器后,4个测点振动加速度均被放大。经过FFT分析,发现振动能量主要集中在低频段。10~315Hz,315~1000Hz,10~8000 Hz 3个频段加速度级,满足要求,但振动烈度偏高。所得试验数据和分析结果对压缩机的动态设计、改造具有指导意义。     

Analysis of the HVAC system’s sound quality using the design of experiments

Human hearing is very sensitive to sound, so a subjective index of sound quality is required. Each situation of sound evaluation is composed of Sound Quality (SQ) metrics. When substituting the level of one frequency band, we could not see the tendency of substitution at the whole frequency band during SQ evaluation. In this study, the Design of Experiments (DOE) is used to analyze noise from an automotive Heating, Ventilating, and Air Conditioning (HVAC) system. The frequency domain is divided into 12 equal parts, and each level of the domain is given an increase or decrease due to the change in frequency band based on the “loud” and “sharp” sound of the SQ analyzed. By using DOE, the number of tests is effectively reduced by the number of experiments, and the main result is a solution at each band. SQ in terms of the “loud” and “sharp” sound at each band, the change in band (increase or decrease in sound pressure) or no change in band will have the most effect on the identifiable characteristics of SQ. This will enable us to select the objective frequency band. Through the results obtained, the physical level changes in arbitrary frequency domain sensitivity can be determined.     

一种新型宽带频率计

在宽带频率范围内首度将预分频法、相检测频法和多周期同步法相结合,在2 Hz～6 GHz的范围内实现了较高精度的频率测量.频率计模块采用高、中、低3个输入通道,功能电路及控制电路在复杂可编程逻辑器件CPLD内完成.该频率计模块基于PXI总线,采用虚拟仪器技术设计了仪器操作软面板.经过仿真和实验,验证了该测量方法的正确性.     

Sound quality change of the automotive engine noise by variation of engine oil condition

Sometimes, engine oil is referred to as a factor that affects engine sound and driving feeling. To investigate the difference of engine noise according to the engine oil conditions in the viewpoint of sound quality, the interior and exterior sound of middle-class sedan with gasoline engine was compared under the different oil conditions. Objective analysis was conducted to find the existence of any appreciable change in psychoacoustic attributes. Loudness, sharpness, and roughness are observed as the important sound quality metrics. It was observed that the noise differences were induced by the oil property, temperature and used time. Basically, the dramatic difference is rarely observed with the difference of initial property of oil. According to change of temperature, lower loudness is observed at the high temperature condition. Comparing new and used oils, the relatively high loudness was observed at idle condition after replacing oil, especially in the low frequency range.