电影音乐节目的电平控制

声音信号的重要计量值为VU值和峰值,它们分别直观反映声音强度及失真情况。为了透彻分析和阐述电影音乐节目制作系统的特性,该文通过实验的方法,测量了大量乐器在典型演奏法下的VU值和峰值。进而通过实验数据的结果,做出P/VU概率分布曲线。各音乐信号的P/VU分布情况决定了系统的电平储备,掌握此结论非常有助于进行电影音乐节目制作过程中的电平控制。     

二值噪声驱动下二阶线性系统的随机共振

研究了二值噪声驱动下二阶线性系统的随机共振问题. 采用平均法推导出系统输出幅值增益的表达式,考察了幅值增益与系统频率、输入信号频率、噪声强度和噪声相关时间的关系,发现系统输出幅值增益随这些参量呈单峰共振变化. 另外,二值噪声的非对称性对共振峰值具有很大影响. 关键词： 随机共振 幅值增益 二值噪声 二阶线性系统     

热电器件综合性能表征系统及实验研究

基于直流瞬态Harman法测量热电器件优值系数原理,搭建热电器件综合性能表征实验系统,实现同时测量热电器件无量纲优值系数（ZT值）、Seebeck系数、电导率以及热导率,并通过Labview编程完成对实验系统的控制、数据采集、实时显示和处理。制作并改进具有夹层结构的热电器件,对此开展了性能测试评估。实验结果表明,室温下夹层结构热电器件ZT值小于常规Bi₂Te₃器件,但Seebeck系数比常规器件大;夹层结构器件电导率和热导率均大于常规器件值。     

CCD二值化测量的阈值自动调节方法

设计了一种利用单脉冲正向峰值探测电路构成的CCD二值化阈值自动调节方法。分析了峰值探测电路产生漂移现象的原因,提出了解决方法。实验结果表明,该方法可达到100倍左右的自动调节范围,实现了野外自然光照明条件下的CCD输出信号二值化阈值的自动调节。     

可调谐半导体激光吸收光谱技术的调制参量影响及优化选择

为获得较好的谐波信号,完成不同测量目的,以DFB-760.77nm波长处氧气监测为例,通过改变扫描锯齿信号和调制正弦信号的频率和幅值,讨论了调制参量对二次谐波信号峰-峰值、对称性、谐波信号展宽和信号完整性等判别依据的影响和变化.结果表明:Sinmulink模拟值和实验值相关性较高,当正弦调制信号和锯齿扫描信号频率比值为1 000倍时,可以获得较好的二次谐波信号.该研究为实验系统中调制参量的选取和调制度及系统准确度、稳定性、重复性等性能的优化提供了一定帮助.     

基于光斑跟踪器的脉冲峰值保持电路的实现

针对激光光斑跟踪器接收信号处理系统中常规A/D采样电路对脉冲电压峰值采集的技术要求,设计了一种脉冲峰值保持电路。通过对该峰值保持电路的各项指标进行理论分析,采用宽带宽跨导放大器MAX436设计该峰值保持电路,并对该电路进行了仿真分析与实验研究,得到满足参数指标设计要求的实验结果:对于脉宽50 ns的激光脉冲信号,在输入信号幅度大于100 mV时,峰值保持电路的响应速度2 ns,下垂速率6.0 mV/s,保持精度1.1%。     

一种改进的奇异值降噪阶次选取方法用于紫外光谱信号去噪的研究

光谱去噪是光谱检测的重要环节。针对光谱信号易受光谱仪热噪声、现场机械振动以及随机噪声等因素影响,而在线监测系统要求减少人为参数选择对去噪效果的影响,提出利用奇异值分解(SVD)理论对光谱信号去噪。提出一种改进的降噪阶次选取方法：指定奇异值差分谱最大峰值点θ₁为所选阶次下界;利用奇异值、奇异值差分谱综合信息选取阶次上界θ₂;将区间θ₁～θ₂定义为模糊区域,通过模糊C均值聚类求取隶属度,赋予模糊区域内奇异值相应的权重系数。用所提方法对不同信噪比下SO₂紫外光谱信号去噪,将信噪比、均方根误差、波形相似系数、平滑度指标用于去噪效果的评价。去噪结果表明：所提方法完全基于数据驱动,具有较好的去噪效果,能够真实的恢复原始信号。     

基于Labview的脉冲漏磁检测系统的研究

研究了一种脉冲信号激励的漏磁检测系统;利用USB数据采集卡I/O口输出脉冲方波信号经过功率放大环节生成激励信号,通过数据采集卡触发采样功能实现检测信号的同步采样;基于Labview软件搭建了漏磁检测虚拟仪器平台,实现了漏磁检测信号的采集、调理、储存、回放和分析功能;通过实验对加工有宽度为2 mm深度分别为2 mm、5 mm、10 mm的3个裂纹缺陷的钢样本进行检测,应用霍尔传感器检测漏磁场信号;检测信号经过调理和采集,在电脑中实时显示漏磁信号随时间的变化波形;通过分析回放采样信号的峰值和峰值到达时间评估缺陷的位置和深度;实验结果表明缺陷深度越大采样信号的峰值越大,峰值到达时间越长。     

光声池中微弱光声信号检测

大气中的污染源气体含量很少, 用光声光谱对其进行监测得到的光声信号极其微弱. 本文首先分析微弱信号产生机理, 在分析Holmes Duffing方程的基础上, 提出了适合光声池微弱信号检测的变尺度差分方法. 该方法通过对信号进行尺度变换, 再做差分来检测微弱信号. 理论分析和实验表明, 变尺度差分方法能很好地抑制系统相空间的共模噪声, 而且能很好地凸显混沌状态临界值. 变尺度差分方法测出的信号相对误差都小于5%, 说明其可以用于较高频率、 相位和频率都未知的微弱光声信号幅值检测. 关键词： 光声光谱 微弱信号 幅值 Duffing     

基于禁忌搜索的正交多相码波形设计

正交多相码信号有低自相关旁瓣值和低互相关峰值的特点,可以用于编队工作的主动声纳中,降低声纳之间的直达波干扰。文章提出用禁忌搜索的方法设计正交多相码信号集,优化正交多相码的自相关旁瓣值和互相关峰值。通过对实验结果的分析和多种算法之间的比较,证明了禁忌搜索算法能够设计相关性能更优的正交多相码。文章还通过数值实验,分析了正交多相码信号集的相关性能与信号数量和码长的关系。     

A model of the VU (volume-unit) meter, with speech applications

The Volume- Unit (VU) meter, used in speech research prior to the advent of computers and modern signal processing methods, is described in signal processing terms. There are no known software implementations of this meter, which meet the 1954 ASA standard and provide the instantaneous needle level. Important speech applications will be explored, such as making comparisons of speech levels to earlier classic works, and measuring speech levels using traditional methods on modern computers. It is our intention to make this venerable method of measuring speech levels available once again. The VU meter is simulated and its properties are studied. A 1950s vintage and a recent vintage VU meter are studied by comparing the transient responses to tones and measurement of speech levels. Based on these measurements, a software VU meter (henceforth referred to as VUSOFT) is simulated, and verified. The method for reading the meter is explained, and simulated in software. The VU level for speech is shown to depend on the reading duration. The relationship between the root-mean-squared (rms) level of a signal and the VU level of a signal is determined, as a function of the meter-reading time.     

电火花声源的某些特性

文中给出了电火花声源的压力波形及其频谱图，着重讨论了储能与压力波峰值P1m,和半峰值之间P1m/2的时间t1之间的关系，以及刚性圆筒内放电时边界对P1m和t1的影响。     

A prediction method of the response probability distribution for arbitrary sound insulation systems

This paper describes a practical evaluation method of the response probability distribution for an arbitrary sound insulation system with a random input noise of arbitrary distribution. Here, the response probability distribution is derived in a fairly simple form using the statistical Hermite expansion-type series expression. The effect of the sound insulation system and the input fluctuation on the resultant probability distribution form is hierarchically reflected in various types of statistics such as the mean, variance and each expansion coefficient. Finally, the proposed evaluation method is experimentally confirmed by applying it to the observed data for typical examples of single- and double-wall insulation system, with white noise and music excitations.     

阵列式双水听器平面扫描声强分布测量和声功率计算实验研究

根据双水听器法测量声强的基本原理，本文提出了基阵在湖中的布放及测量声强分布的实施步骤。通过对试验数据的处理与分析，给出了声强分布的三维力和等值曲线图，并利用扫描平面上的声强分布。计算出声源辐射的声功率。实验表明，本文提出的用列阵式双水听器声强测量系统，作平面扫描测量声强分布的方案是合理的；利用所测得的双平面近场声强分布来计算源的辐射也是可行的。     

Acoustic method for measuring air temperature and humidity in rooms

A method is proposed to determine air temperature and humidity in rooms with a system of sound sources and receivers, making it possible to find the sound velocity and reverberation time. Nomograms for determining the air temperature and relative air humidity are constructed from the found sound velocity and time reverberation values. The required accuracy of measuring these parameters is estimated.     

Acoustic comfort in large dining spaces

This study carried out a questionnaire field investigation in two typical large dining spaces. The results suggest that the acoustic comfort of diners has an influence on the comfort evaluation of the overall dining environment, and background noise is an important factor affecting the acoustic comfort evaluation of diners. The role of various individual sound sources in background noise has been investigated, considering general background music, speech sound, activity sound, and mechanical noise, and it has been revealed that background music, other diners’ speech sound and tableware’s impact sound has a dominant impact on the acoustic comfort evaluation of diners. Compared with the existence of background music in background noise, diners’ acoustic comfort evaluation is higher than that without background music. The loudness, articulation, noise level and preference degree of various individual sound sources are factors which affect diners’ acoustic comfort evaluation on sound sources. In terms of demographic and social factors, gender and the frequency of dining out have a significant impact on diners’ acoustic comfort evaluation.     

椰胡声功率级的半消声室测试

椰胡是具有地方特色的拉弦乐器之一,多用于演奏广东音乐和广东戏曲、曲艺的伴奏。但对其发声强度一直未进行过科学的测试。本文介绍在华南理工大学半消声室内参照ISO(GB)标准对椰胡声功率级的测量工作。由两位资深乐师分别用两把椰胡在pp,mp,f和ff力度下演奏单音、音阶和乐曲,对每一把椰胡的每一测试内容,由十通道测试设备同步测试中心频率为100～10000 Hz的1/3倍频带声压级谱,通过计算获得每把椰胡在演奏每项内容时的声功率级和动态范围。通过对两把椰胡的测试结果进行平均,获得该乐器在演奏上述内容时的典型声功率级数值及频谱。文中并将半消声室内的测试结果与混响室内的测试结果相对比,探讨测试环境对测试结果的影响。民族乐器发声强度及其频谱特性的获得是开展民族音乐厅堂音质研究的基础。     

考虑基底热传导的石墨烯薄膜热声理论

主要基于热声效应对石墨烯薄膜发声进行理论研究。首先建立了石墨烯薄膜耦合热振动模型,推导出了石墨烯薄膜发声器的声压表达式。在此基础上,进行了不同基底石墨烯薄膜发声器的声压测试,并将测试值与理论计算结果对比,二者随频率变化趋势基本吻合,测试值略低于理论值,验证了推导出的声压表达式的正确性。研究表明石墨烯薄膜发声器有很宽的频域响应,在低频段声压级随频率增大而增大,在高频段响应平稳,具有作为优秀的热致发声器的潜力。基底材料蓄热系数越小,石墨烯薄膜的声压值越大;声压级随薄膜热容量的增大而减小。研究结果对于石墨烯的发声机制探索及其在扬声器设计等方面的应用具有指导意义。      

Anomalous vibrational states of a monatomic surface film

Vibrational states of a one-dimentional chain of atoms which models peculiarities of a monatomic surface film are considered. A set of nontrivial equilibrium states of the system is determined in whose vicinity almost linear band vibrations are possible. Peculiarities of anomalous branches of vibrational states are discussed. It is shown that the low-frequency gap of vibrational states disappears under certain conditions. This determines the possibility of appearance of low-frequency sound vibrations which are not possible for a trivial equilibrium distribution of atoms in the film.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika No. 7, pp. 22–25, July, 1982.     

Subjective diffuseness of music signals convolved with binaural impulse responses

The spatial impression of sound in a hall can be quantified using sound field factors such as the interaural cross-correlation coefficient (IACC) calculated from binaural impulse response (BIR), henceforth denoted by IACC_IR. The subjective diffuseness for the listener is a spatial attribute which depends on factors associated both with the source signal and with the actual sound field, and is quantified using the IACC of the signal received by the listener, henceforth denoted by IACC_SR. Therefore, the subjective diffuseness in a given hall may change with the music. The aims of this study are to estimate the IACC_SR from the IACC_IR and the factors, which is obtained from autocorrelation function (ACF) of music signal, and to evaluate the subjective diffuseness by these factors. First, the relationship between the IACC_IR and IACC_SR was investigated. Second, subjective diffuseness was measured by a psycho-acoustical experiment. As a result, the IACC_SR could be estimated from the IACC_IR of the BIR and the effective duration (τ_e) from the ACF of music signal. It was found that the effects of BIRs on subjective diffuseness could be evaluated by IACC_IR for almost all subjects, while the effects of music signals could be evaluated by the τ_e and the width of the peak at τ=0 (W_?(0)) of the ACF.