声波干涉可闻其声见其“影”

如图1所示，信号发生器产生音频信号，经放大后由两音箱发出相同频率的声波形成干涉，在干涉区域接收装置将接收到的声波转化成电信号，经放大送入指示电路，接收点接收声波的强弱可由指示电路显示出来，因此，可以显示干涉“条纹”的存在。     

声波干涉的实验

声波干涉实验获得成功的关键:在于有一个相干波源。过去用音叉作声源,因音量太小,效果不够理想。现在我们用电声源做此实验,效果很好。仪器的构造:分为发声和支架两部分。1.发声部分:可以用音频讯号发生器,在其输出端串接两只相同的小型喇叭T_1和T_2(口径在1.5时以下)组成,也可以自制或使用     

声波干涉实验的设计与演示

在现行的中学物理教材和师范物理教科书中都没有声波干涉的演示实验，只是列举实际生活中的一些现象，来说明产生这些现象的原因是由于声波的干涉引起的，缺乏直观性。例如，某教材中讲到声波的干涉时，是这样举例分析的：“操场上安装两个相同的扬声器，当它们发出相同频率的声波互相叠加时，会产生振动加强和振动减弱的区域，因此，在操场上某些地方听到的声音大，在另外一些地方听到的声音小，这是声波的干涉现象。”     

基于多层石墨烯材料的光纤声波传感器

研究了一种基于多层石墨烯材料的光纤声波传感器,该传感器是由单模光纤和多层石墨烯薄膜构成的光纤法布里-珀罗干涉腔结构。分别采用多层的石墨烯和氧化石墨烯(GO)材料作为声压敏感薄膜,进行声波传感实验研究。结果表明,在音频范围内,基于石墨烯和GO薄膜的光纤声波传感器的平均信噪比分别达到56dB和69dB,平均最小可探测声压灵敏度分别为20.8μPa·Hz~(-1/2)和6.63μPa·Hz~(-1/2),远低于电学声波传感器的最小可探测声压灵敏度。基于石墨烯材料的光纤声波传感器具有更高的声波检测灵敏度,适用于强电磁干扰、狭小空间等环境下的微声压测量。     

声波干涉的演示

声波干涉的演示陈建（江苏省南通师范学校２２６００６）器材音频讯号产生器（音讯－１甲型）、低频放大器、教学示波器、话筒及扬声器两只．演示方法将各仪器按附图连接，音频讯号产生器的“输出总阻”旋钮置于“５０Ω”，“频率范围”旋钮扳到“２００—２ｋＨｚ”档，...     

基于Lab view声卡音频演示拍现象

介绍了利用Lab view演示声波拍现象方法,设计基于声卡的Lab view双通道信号发生器产生两个频率接近的音频信号,分左右声道驱动两个喇叭,相当于两个振源,即形成拍音,并利用信号发生器测量拍频。     

声波在双层非线性介质中传播的二极管现象

假设声波在双层一维非线性系统中传播时线性部分满足波动方程,非线性部分类似于非线性薛定谔方程的非线性部分.对该模型正反两个方向分别入射相同的声波计算透射率发现:一定频率及强度的声波在模型中具有单向透过性,表现出声二极管的行为;随着非线性强度差异的增强,单向导通性显著提高.     

基于智能手机实现典型声学现象的课堂多边互动模式

利用智能手机的音频发送和接收功能,编写声波合成与拍的现象以及多普勒效应等典型声学效应演示的APP程序,并将该演示程序应用于大学物理课堂教学或者声学有关的物理实验教学之中,探索了课堂多边互动的新模式.     

一种减小尺寸的声彩虹捕获效应结构*

该文提出了一种减小尺寸的彩虹捕获效应结构,在铁板上刻上深度相同的空气凹槽阵列并加入周期性缝板单元,通过调节缝宽得到不同的等效折射率。该文对1000 Hz～2000 Hz的声波进行仿真实验,仿真结果表明不同频率的声波被局域在不同的位置,即实现了彩虹捕获效应。由于局域处声波群速度很小,局域处声场能量得到很大的提升。相对于传统的深度渐变的空气凹槽结构,我们的结构尺寸更小,可调性更强,更容易实现对低频声波的捕获效应。该结构具有能量加强和声波空间分离的效应,相信在声吸收、声波识别等领域有着潜在的应用前景。     

用脉冲重叠法精确测定表面声波的传播速度

本文提出采用交叉触发脉冲重叠法来精确测定材料的表面声波相速度.在一块样品上制作相同的三个叉指换能器A、B、C,在B与C之间的样品表面镀上金属膜.分别依次由A或C发射表面声波,而由其它两个换能器接收,即可测定表面声波的速度和速度变化.本文对LiNbO,石英及压电陶瓷样品进行了测量,测量精度估计约为±2m/s.     

大功率调制气流声源阵列的相干合成实验研究

完成了调制气流声源阵列的相干合成实验. 提出了利用主动相位控制方法实现调制气流声源阵列相干合成的思路, 介绍了基于随机并行梯度下降算法的声源阵列相干合成的原理. 对利用该算法实现声源阵列的相干合成进行了数值模拟, 完成了双调制气流声源阵列在远场的相干合成实验, 并给出算法参数的合理设置方案. 实验结果显示, 基频成分的相干合成效果明显, 算法收敛时测点处的声压级相比单源发射增加了4 dB, 接近于各单源功率谱中基频成分相干合成、其他频率成分非相干合成的结果; 结果表明实验中算法能够有效控制各调制气流声源辐射声波的相位, 取得了明显的相干合成效果. 关键词： 调制气流声源 相干合成 随机并行梯度下降 高阶谐波     

Measuring the neck frequency response function of laryngectomy patients: implications for the design of electrolarynx devices

Measurements of the neck frequency response function (NFRF), defined as the ratio of the spectrum of the estimated volume velocity that excites the vocal tract to the spectrum of the acceleration delivered to the neck wall, were made at three different positions on the necks of nine laryngectomized subjects (five males and four females) and four normal laryngeal speakers (two males and two females). A minishaker driven by broadband noise provided excitation to the necks of subjects as they configured their vocal tracts to mimic the production of the vowels /a/, /ae/, and /I/. The sound pressure at the lips was measured with a microphone and an impedance head mounted on the shaker measured the acceleration. The neck wall passed low-frequency sound energy better than high-frequency sound energy, and thus the NFRF was accurately modeled as a low-pass filter. The NFRFs of the different subject groups (female laryngeal, male laryngeal speakers, laryngectomized males, and laryngectomized females) differed from each other in terms of corner frequency and gain, with both types of male subjects presenting NFRFs with larger overall gains. In addition, there was a notable amount of intersubject variability within groups. Because the NFRF is an estimate of how sound energy passes through the neck wall, these results should aid in the design of improved neck-type electrolarynx devices.     

声速测量及声波干涉演示仪器的研制

本介绍了声波干涉、反射的两种物理演示仪器的研制,一种是通过调节波导管中液面的高度形成驻波,实现对声速的测量;另一种是由一个信号发生器驱动两个扬声器,这两个相干的声源在自由空间中形成强弱变化的声波干涉。本分别介绍了这两种装置的原理、制作及使用效果。     

A study of sentence stress production in Mandarin speakers of American English

Acoustic characteristics of American English sentence stress produced by native Mandarin speakers are reported. Fundamental frequency (F0), vowel duration, and vowel intensity in the sentence-level stress produced by 40 Mandarin speakers were compared to those of 40 American English speakers. Results obtained from two methods of stress calculation indicated that Mandarin speakers of American English are able to differentiate stressed and unstressed words according to features of F0, duration, and intensity. Although the group of Mandarin speakers were able to signal stress in their sentence productions, the acoustic characteristics of stress were not identical to the American speakers. Mandarin speakers were found to produce stressed words with a significantly higher F0 and shorter duration compared to the American speakers. The groups also differed in production of unstressed words with Mandarin speakers using a higher F0 and greater intensity compared to American speakers. Although the acoustic differences observed may reflect an interference of L1 Mandarin in the production of L2 American English, the outcome of this study suggests no critical divergence between these speakers in the way they implement American English sentence stress.     

Propagation and radiation of sound in a finite length duct

An analysis has been carried out to investigate sound transmission in an unflanged circular duct of finite length. A new formulation for calculating the generalized radiation impedance of the opening of a finite length duct with a spinning source inside is presented. The effect of interference between the duct apertures at its two ends is identified in the calculations of radiation impedance, reflection coefficient, and the far field radiation pattern. The results show that the degree of interference between the two ends reduces for high frequency waves and/or for long ducts. Further, the interference effects on the far field for spinning sound are more serious than those for non-spinning sound.     

使用脉冲声和矢量传声器的现场测量吸声系数

使用不同声源利用矢量传声器对毛毡材料进行现场吸声系数测试,研究了不同背景下不同声源的抗噪能力。矢量传声器可以同时测得声压和质点振速信号,进而可计算得到阻抗,利用自由空间和材料表面的阻抗可计算得到材料的吸声系数。在此次实验中,使用不同声源分别在无干扰和有一白噪声干扰源的两种情况下进行测试。结果表明,使用对数扫频脉冲和巴特沃斯脉冲测试所得的吸声系数曲线更平滑,说明脉冲声可以有效降低环境反射的影响,在高噪声背景下使用对数扫频脉冲测试所得的结果基本没有受到背景噪声的影响,说明对数扫频脉冲的抗噪能力更强。因此,使用对数扫频脉冲作为声源进行测试可有效减弱环境反射和背景噪声的影响。     

深海中利用单水听器的影区声源无源测距测深方法

在典型深海情况下当声源与接收水听器位于海水表层时,在影区内由声源海底接收器、声源海面海底接收器、声源海底海面接收器和声源海面海底海面接收器4条声线形成声场干涉结构,声强随着频率具有两种干涉周期,随着收发距离的增加而增大,分别随着声源深度、接收水听器深度的增加而减小。因此由单水听器记录的声场干涉结构即可实现宽带声源目标的无源测距测深,仿真分析验证了其有效性。在南海深海声学实验中观测到海面宽带噪声源在声场影区所形成的声场干涉结构,数据分析结果验证了深海声场干涉结构用于声源无源定位的有效性。与传统无源定位方法相比,该方法不需要宽带引导声源、精确的海底声学参数和大规模的拷贝场计算。      

Aerodynamic and acoustic characteristics of the adult AfricanAmerican voice

Laryngeal aerodynamic and acoustic characteristics of African American voice production were examined from vowel samples produced by ten adult female and ten adult male speakers. The data were compared with that for a control group consisting of ten adult female and ten adult male White speakers, matched for age, height, and weight. All measures were analyzed using Cspeech 4.0. Aerodynamic measurements, extracted from a glottal airflow waveform, included maximum flow declination rate, alternating glottal airflow, minimum glottal airflow, and airflow open quotient. Acoustic measures included fundamental frequency and sound pressure level. No significant mean differences between the African American and White speakers were found, except for maximum-flow declination rate. The White speakers produced significantly higher declination rates than the African American speakers. The factor of sex for the African American speakers was statistically significant for the measures of maximum-flow declination rate, alternating glottal airflow, open quotient, and fundamental frequency, consistent with the functioning of the White speakers. The results suggest that during vowel production, where the vocal tract is in a fairly static position, acoustic and aerodynamic characteristics for African American and White Speakers are comparable.     

The possibility of reconstruction of two-dimensional random inhomogeneities in a shallow sea by frequency shifts of the spatial interference structure of the sound field

Fluctuations of frequency shifts of the spatial interference structure of the sound field in the oceanic waveguide, caused by a two-dimensional field of a random perturbation, are described. Various schemes of observation point spacing are considered. The possibility is shown to reconstruct the spatial spectrum of waveguide perturbations by measuring the spatial spectrum of the frequency shift of the interference pattern. The results of the theoretical treatment are illustrated by the examples of background internal waves and bottom roughness. The sensitivity of monitoring based on measurements of frequency shifts of the interference structure of the sound field is estimated. For medium perturbations by background internal waves, the fluctuations of liquid layer vibrations, sound speed, and temperature, which are minimum detectable by frequency shifts of the interference pattern, were estimated.     

Possibility of reconstructing hydrological variability of shallow sea by measuring frequency shifts of interference structure of sound field

Variations in the vertical space-frequency interference structure of the sound field in the oceanic waveguide are described. Reconstruction algorithms of sound speed field, based on information on frequency shifts of interference maxima of the sound field, are presented.