利用扫频音的刺激频率耳声发射实验研究

耳声发射是一种可以被记录的弹性波能量，产生于耳蜗，可以用于检测耳蜗外毛细胞的健康 情况。目前，临床上使用的瞬态诱发耳声发射和畸变产物耳声发射各有优缺点，而该文研究的对象是一种比其他耳声发射应用更广泛的刺激频率耳声发射(Stimulus Frequency Otoacoustic Emissions， SFOAE)。因此，该文提出了一种基于扫频的 SFOAE 测量方法。所谓扫频是一种频率随时间线性变化的刺激声，利用其所测量的 SFOAE 频率范围更宽，而分辨率取决于扫频率。该文中，首先，采用三间隔范式产生 SFOAE，并用跟踪滤波器从背景噪声中提取扫频 SFOAE。其次，依次通过对相同实验对象在不同时间所测得结果、与传统方法结果和对不同扫描时间所测得结果进行对比，以验证扫频 SFOAE 的可靠性、兼容性和有效性。研究结果表明，所提出的 SFOAE 可以用于改进临床上现有的听力损失的检测方法。     

基于短声和扫频音的听觉脑干诱发电位比较研究

听觉脑干诱发电位检测(Auditory Brainstem Response,ABR)是一种客观检测听力损失的常用方 法。短声作为一种宽频信号,其诱发的 ABR 通常被认为是 ABR 检测的金标准。但由于人体耳蜗基底 膜行波具有延迟特性,短声不能同时刺激整个耳蜗基底膜产生兴奋,导致诱发的 ABR 波形因不同相而 产生衰减。为解决这一局限性,该研究设计了一种扫频音刺激,根据耳蜗基底膜的延迟特性重新调整 不同频率成分出现的时间,以诱发 ABR 信号。实验通过将所设计的扫频 ABR 方法和传统的短声 ABR 方法的波质量进行比较发现,在不同的刺激强度和刺激速率下,扫频 ABR 的波形形态均明显优于短声 ABR 的。此外,在不同的响应叠加次数下,所设计的扫频音比短声诱发 ABR 能更快地诱发出 ABR 波 形。该文所提出的扫频 ABR 方法有望提高 ABR 在听力损失诊断中的灵敏度。     

纯音听力计中纯音信号发生器的设计与实现

纯音听力计是进行听觉功能测试的基本声学仪器,而纯音信号发生器是其最重要的组成模块,它决定着可控声源的质量,直接影响测试结果的准确性;文章分析了现有纯音信号发生器存在的问题,提出了一种基于微处理器ATMEG128的设计与实现方法;该发生器可生成频率在125Hz~8kHz、听力级为-10~120dB的精密纯音信号;其中,频率按1/3倍频程输出,听力级的最小调节精度可达0.5 dB,符合国家标准。     

非接触式光纤声发射传感器的设计

为克服常用声发射传感器必须和被测物体接触、工作频带较窄且带内幅频特性波动较大和易受电磁干扰的不足,提出采用光纤干涉仪原理研制声发射传感器.介绍了光纤声发射传感器的原理、系统组成.其频率范围为100kHz～1.4MHz,振幅分辨率为0.08nm.     

微弱信号混沌检测的自跟踪扫频控制方法

当利用混沌理论进行微弱信号的检测时,针对不同频率的信号只能分别构建不同的检测系统进行检测,势必使其检测效率低下.本文阐述了一种分频段阈值变换的混沌检测方法,并基于该方法实现了自跟踪扫频检测.为此,首先分析了微弱信号混沌检测方法中的变阈值法和定阈值法,指出了这两种方法的优缺点,然后提出了分频段阈值变换的混沌检测方法,并基于该方法开展了微弱信号的自跟踪扫频检测控制的研究,设计制作了微弱信号自跟踪扫频检测控制电路,并进行了微弱信号自跟踪扫频混沌检测的实验研究.结果表明该检测控制系统可以实现在噪声背景下的中低频率微弱周期信号的自跟踪扫频检测.     

声表面波温度传感器频率分级扫描方法研究

针对声表面波(SAW)谐振腔体的频率响应单侧单调特征,为提高传感器的温度响应速度,提出了一种频率分级扫描方法,将频率扫描分为粗扫频和精扫频两个阶段,以不同的扫频步长依次进行.利用粗扫频确定中心谐振频率所处的频率区间,再在该频率区间内利用精扫频得到腔体中心谐振频率,可将温度传感器扫频时间降为原来的1/7.利用提出的频率扫描方法开展实验研究,分别研究了单个传感器的温度量测不确定度和多个传感器的温度量测一致性,并分析了实验结果.     

非接触光纤声发射传感器的设计

为克服常用声发射传感器必须和被测物体接触,工作频带较窄且带内幅频特性波动较大和易肥电磁干扰的不足,提出采用光纤干涉仪原理研制声发射传感器,介绍了光纤声发射传感器的原理,系统组成。其频率范围为１００ｋＨｚ－１．４ＭＨｚ,振幅分辨率为０．１８ｎｍ。     

基于时间反转聚焦的声发射源定位算法

声发射检测可以判断损伤的活性和严重性而被广泛应用,但对损伤位置仍没有更准确的定位方法。提出一种基于时间反转理论的声发射源准确定位的方法。根据声发射被动监测的特点,研究采用时间反转聚焦方法使声发射信号能量叠加放大,提高信号的信噪比,并分析推导了具体损伤声源信号时间反转聚焦增强过程;利用时间反转对声发射源的自适应聚焦能力,重建信号传播波动图,通过信号聚焦显示出损伤声源位置和区域;最后通过数值仿真对该方法进行验证,仿真结果表明能有效提高损伤声源信号的能量,能够对检测区域的信号重建,并通过显示准确给出损伤声源位置,定位精度较常规时差定位法有较大提高。     

LabVIEW下的扫频阻抗测试系统稳定性研究

扫频阻抗法是一种新型的检测变压器绕组变形的方法,它结合了短路阻抗法和频响法的优点。由于信号发生器以及采集卡的精度有限,扫频阻抗测试系统存在50 Hz短路阻抗值测试稳定性低、准确度不高的情况,从而导致对于变压器绕组变形情况的误判。利用Lab VIEW编程调用程控宽频带信号发生器以及高速采集卡,在信号发生器准确度有限、环境中存在工频干扰的条件下,针对扫频阻抗曲线在低频段为线性这一特性,采用多种测试方法进行测试。从频率准确度、测试平均误差、测试耗时等方面评估了几种方法,并从中选取了一种能够有效减小信号发生器频率误差、提高扫频阻抗测试结果稳定性的方法。该方法可将扫频阻抗测试中50 Hz短路阻抗测试的平均误差由0.526%降低至0.119%,同时消除了由于信号发生器带来的频率误差。     

基于小波分解与希尔伯特-黄变换的跳频信号检测

现有的基于时频分析的检测方法在时间分辨率和频率分辨率上往往不能同时满足要求,针对这一问题,提出了一种结合小波分解与希尔伯特-黄变换(HHT)的跳频(FH)信号检测方法.利用小波分解去除混合信号中的噪声;利用希尔伯特-黄变换实现跳频信号的检测,避免了传统时频分析过程中窗函数的影响.理论推导和仿真实验表明:本文方法能同时有效地兼顾时间分辨率和频率分辨率,明显改善了跳频信号检测的准确性.     

Synergistic effects of noise and hand-arm vibration on distortion product otoacoustic emissions in healthy subjects

An experimental study has been performed on the effect of exposure to noise (N), vibration (V), and combined noise and vibration (NV), on the distortion product otoacoustic emission (DPOAE) level. The aim of the study is investigating the possible synergistic effect of noise and vibration, increasing the risk of damage to the hearing function due to noise only.Twelve normal-hearing volunteers were randomly exposed to hand arm vibration (HAV) only, noise only, and HAV and noise simultaneously. The exposure consisted of five consecutive sessions interspersed with quiet periods. DPOAEs were recorded during the quiet intervals following each exposure session, and during recovery, and compared to their baseline level, and among different test treatments. An ad hoc acquisition system developed in Labview was used to record high frequency-resolution DPOAE spectra in a suitably short time. Time-frequency filtering, based on the wavelet transform, was used to separate the DPOAE components coming from different generation mechanisms.The three test treatments, N, V, and NV, yielded significantly different results. The condition affecting most significantly all DPOAE component levels was the exposure to vibration only, causing a statistically significant increase of the signal level during all the exposure periods, with a decreasing trend during recovery. Also the exposure to noise only, N, caused a DPOAE level increase, statistically significant for the long latency (LL) DPOAE component. Only when exposure to noise was in combination with vibration, the zero-latency (ZL) component was clearly suppressed during the exposure. The results suggest a synergistic adverse effect of noise and vibration on the cochlear function.Relevance to industryThe simultaneous exposure to noise and hand arm vibration is a very common industrial scenario. The risk that exposure to mild noise levels could interfere with the exposure to vibration, enhancing the adverse effect on the hearing function, should be considered to optimize prevention strategies at the workplace.     

Interactive Evolutionary Computation-Based Hearing Aid Fitting

An interactive evolutionary computation (EC) fitting method is proposed that applies interactive EC to hearing aid fitting and the method is evaluated using a hearing aid simulator with human subjects. The advantages of the method are that it can optimize a hearing aid based on how a user hears and that it realizes whatever+whenever+wherever (W³) fitting. Conventional fitting methods are based on the user's partially measured auditory characteristics, the fitting engineer's experience, and the user's linguistic explanation of his or her hearing. These conventional methods, therefore, suffer from the fundamental problem that no one can experience another person's hearing. However, as interactive EC fitting uses EC to optimize a hearing aid based on the user's evaluation of his or her hearing, this problem is addressed. Moreover, whereas conventional fitting methods must use pure tones and bandpass noise for measuring hearing characteristics, our proposed method has no such restrictions. Evaluating the proposed method using speech sources, we demonstrate that it shows significantly better results than either the conventional method or the unprocessed case in terms of both speech intelligibility and speech quality. We also evaluate our method using musical sources, unusable for evaluation by conventional methods, and demonstrate that its sound quality is preferable to the unprocessed case     

基于圆结构光的复杂深孔内轮廓尺寸测量方法

涡流法、超声法测量深孔截面轮廓尺寸精度低,而光学单点扫描法测量效率低。介绍了一种基于圆结构光的复杂深孔内轮廓3维测量系统,提出了一种采用FFT分析和差分分析进行测试数据处理的方法,能够实现快速高精度测量。测试系统主要由圆结构光发生器、扩束锥镜、成像锥镜、镜头和CCD组成,对于获取的每一幅被测截面的结构光图像,首先提取光条中心,对光条中心上的点作最小二乘法拟合获取光条中心拟合圆心,并以此圆心点将光条中心线展开,展开波形中存在整体形状误差,主要由圆心偏心误差、椭圆形状误差两个周期性误差分量构成,由于二者振动频率与细节分量的振动频率不相同,借助于FFT分析,将两个误差分量分离出来,进而采取措施减小其对系统的影响;差分分析用于去除阴线和阳线之间的过渡线。该方法提高了阴线圆与阳线圆尺寸计算的精度和效率,实验结果表明,系统内径测量精度达到005mm。     

基于压缩Voxel模型的五坐标数控加工仿真新方法

文章介绍了一种基于压缩Voxel模型的五坐标数控加工仿真新方法。该方法采用压缩Voxel模型表示数控加工工件模型和刀具空间扫描体模型,计算机内部存贮空间小,布尔操作简单、速度快。通过MarchingCubes方法提取数控加工仿真工件表面三角网格模型并进行图形显,提高了仿真工件显示质量。文章同时提出了一种基于压缩Voxel模型的刀具空间扫描体构造新方法,通过构造基本几何体球体、圆柱体、圆环体、锥形体和鼓形体的空间扫描体,完成各种加工刀具棒刀、球头刀、环形刀、锥形刀和鼓形刀空间扫描体压缩Voxel模型。该方法在《基于压缩Voxel模型的五坐标数控加工仿真系统》中得到了应用,仿真结果三维信息完备,操作人员可从任意方向观察、验证仿真结果,克服了现有五坐标数控加工仿真方法和商品化软件系统的不足,该方法是虚拟数控加工的关键技术。     

The statistical measurements and neural network analysis of the effect of musical education to musical hearing and sensing

This work presents the help of music education to musical hearing, the sensing of hearing at the end of education, and the affection of hearing levels of young people. In this study, neural network is used for classification of students using musical hearing and sensing. We demonstrate that machine learning can be used to predict the students musical perception, who entered to the Education Faculty, using neural networks. The pure tone audiometric measurements were realized for the evaluation of hearing at the frequencies 250, 500, 1000, 2000, and 8000 Hz. The evaluation of musical hearing for the students was achieved as: single tone-vertical hearing, poly tone-horizontal hearing and melody and rhythm hearing. The testing of musical hearing and sensing of students were compared with the test after two-year education. It was observed that the tests after two-year education offered good performances at all frequency level and this is meaningful in statistically, While musical hearing sensitivity is significantly high in horizontal and rhythm hearing tests, it is not changed in vertical hearing tests. Our results show that by using musical hearing and sensing our neural network classifies students whether they are at musical Education Department or other educational department of Education Faculty at a success rate of 92% and 88%, respectively.     

Audibility of reverse alarms under hearing protectors for normal and hearing-impaired listeners

The question of whether or not an individual suffering from a hearing loss is capable of hearing an auditory alarm or warning is an extremely important industrial safety issue. The ISO Standard that addresses auditory warnings for workplaces requires that any auditory alarm or warning be audible to all individuals in the workplace including those suffering from a hearing loss and/or wearing hearing protection devices (HPDs). Research was undertaken to determine how the ability to detect an alarm or warning signal changed for individuals with normal hearing and two levels of hearing loss as the levels of masking noise and alarm were manipulated. Pink noise was used as the masker and a heavy-equipment reverse alarm was used as the signal. The rating method paradigm of signal detection theory was used as the experimental procedure to separate the subjects’ absolute sensitivities to the alarm from their individual criteria for deciding to respond in an affirmative manner. Results indicated that even at a fairly low signal-to-noise ratio (OdB), subjects with a substantial hearing loss [a pure-tone average (PTA) hearing level of 45-50 dBHL in both ears] were capable of hearing the reverse alarm while wearing a high-attenuation earmuff in the pink noise used in the study.