民族器乐主观混响感差别阈限的测量

运用恒定刺激法测量了主观混响感的差别阈限,并通过一系列的实验检验了数据的有效性.实验素材为中国民族器乐中典型弹拨乐器、拉弦乐器、吹奏乐器独奏作品,受试人为音响技帅、音响工程专业学生、声学所研究生.实验发现主观混响感的差别阈限为25%左右,受试人群体的类型对实验结果有影响,实验素材对结果的影响不显著.     

混响感知的听觉心理

综述了中国传媒大学传播声学研究所近年来在混响的主观感知机理上的研究工作和进展,涉及混响感的语意调查与分析,音乐听闻的混响偏爱度实验,混响感的差别阈限,混响感的因素分析,以及混响处理与音乐情感之间的相互影响等研究结果。对混响感知的研究对进一步探究在有界空间中主观听感的生理心理机制是十分有启发的。     

汉语语境下混响感的语意调查与分析

探讨了汉语语境下混响和混响时间的定义问题。对两组具有声频工程和建筑声学专业背景的人员进行了主观混响感语意因素重要性的问卷调查,分析了听者个人背景对汉语语境下的混响感语意理解的影响。在实验室初步测量了混响时间与混响感之间的听觉心理关系。语意调查和听觉实验结果揭示出混响时间并不是唯一决定主观混响感的因素,混响感的构成有更为复杂和多元的机理,而且与听者的个人背景和经验有关。      

无顶空间内混响感特性的研究

混响时间是反映时间域内声能衰变率的参量,它大体上可反映扩散空间内的主观混响感。但是,对于庭院等无顶空间而言是否适用,值得研究。因为在这些空间内,声能衰变过程中缺失了大量来自顶面的反射声,虽然混响时间可能变化不大,但会显著影响主观听觉上混响的感受。本文通过模拟声场的主观试听实验,发现反射声的方向性因素不可忽略,其对混响感有明显影响。由于混响时间是以单声道收录为界定的,因此,它不能充分反映无顶空间内的主观混响感。      

视觉刺激条件下的听感差别阈限测量

视听交互的重要性日益突出,但视觉刺激对听觉感知的影响尚缺乏全面深入的研究。以视觉刺激下人耳对声音的主观听感差别阈限变化为研究对象,在主观听觉实验中施加颜色、质量、亮度、运动状态四个不同属性视觉刺激,同时测量纯音信号的响度、主观音长和音高的听感差别阈限。通过与无视觉刺激下相应差别阈限的比较,分析不同视觉条件对响度感知、主观音长感知、音高感知能力的影响。实验数据显示,施加视觉刺激后主观听觉感知的差别阈限值增大,主观音长、音高和响度的差别阈限值平均分别提高了45.1%,14.8%和12.3%。进一步分析的结果表明,施加视觉刺激后基本的听觉感知能力呈下降趋势。同一视觉属性的不同水平视觉条件对听觉感知的影响程度不同,主观听感的变化呈现出一定的规律性,即视觉刺激越舒适,听感的差别阈限变化越小。      

混响室条件下临界辐射干扰场强计算模型

为解决均匀场与混响室内辐射敏感度测试结果相关性较差的问题,利用统计学理论对混响室内场强直角分量及天线接收功率的统计特性进行分析,理论推导出基于受试设备干扰概率的混响室条件下临界辐射干扰场强计算模型。为验证该模型的正确性,以ETS 3142E型天线为受试设备分别在混响室及均匀场中进行临界辐射干扰场强测试,实验结果表明,利用该计算模型得出的临界辐射干扰场强值与均匀场测试结果吻合良好,平均相对误差可控制在2 dB以内,可将该模型应用于实际辐射敏感度测试。     

环境噪声对儿童短时记忆力和注意力的影响

通过实验室研究探讨了不同噪声源在不同声压级条件下对儿童短时记忆力和注意力的影响。在每一个实验中都选取了30名710岁的儿童作为被试,在他们完成相应认知任务的同时,用耳机随机播放3565 dBA的交通噪声、白噪声和空调噪声,考察各种噪声条件对被试认知成绩和主观烦恼度的影响。研究结果表明,噪声对儿童的影响主要体现在主观烦恼度的变化上,不同的噪声条件并没有引起作业成绩的显著差异。影响儿童主观烦恼度的主要因素是声压级,随着声压级的增大,儿童的烦恼度会增加,当声压级在4550 dBA时,儿童对噪声开始产生烦恼感,当声压级在6065 dBA时,儿童对噪声产生了较显著的烦恼感。声压级对儿童烦恼度的影响没有随着噪声源的改变而改变。在相同的噪声条件下,短时记忆力实验中儿童的主观烦恼度都高于注意力实验,说明随着认知过程复杂程度的增加,噪声引起的烦恼度会相应增加。      

海洋混响信号的自适应非线性预测

基于非线性动力学对海洋混响建模,提出了一种自适应非线性预测方法,通过设计一个滤波器来逼近混响信号在相空间的演化轨迹;采用在不同海域进行的两次海上实验获取的混响信号,对自适应预测方法进行验证,其单步预测结果与实验信号符合较好;以模型的单步预测误差作为检验统计量来检测混响中的目标回波,可以在一定程度上抑制混响干扰,提高信混比.     

深海本地界面混响平均强度模型与规律分析

为揭示深海多途传播效应及界面参数对本地界面混响强度的影响规律,将界面混响表述为不同多途混响衰落过程的非相干叠加结果,并结合界面散射的若干物理机制,建立了以海面海底物理参数为变量的混响强度模型.通过数值仿真和理论分析研究了不同多途混响强度的衰落特性、到达角的空间分布及部分物理参数对混响强度的影响,并利用南海海盆(典型泥质海底)实验数据对模型有效性进行验证.仿真结果表明,界面混响强度随时间变化呈现多峰结构,峰值时间与多途混响的到达时间分布一致。声源与接收器均位于近海面处时,首峰的峰值强度及其衰落过程由海面风速决定,其它峰的峰值强度由海面海底参数共同决定,但其衰落过程主要受到底质参数的影响.      

偏度最大化多通道逆滤波语音去混响研究*

房间混响会降低语音质量和语音可懂度。高阶统计量是衡量非高斯性的重要参量,基于语音非高斯特性可实现语音去混响。本文提出一种基于高阶统计量的多通道语音去混响方法,该方法首次用多通道语音信号线性预测残差的三阶统计量偏度（Skewness）构造代价函数,以去混响重建信号线性预测残差的偏度最大化为目标自适应地更新逆滤波器;同时结合语音信号的产生模型,提出基于偏度准则的线性预测与房间脉冲响应逆滤波联合估计方法,进一步提高去混响算法性能。实验结果表明,该方法相较于已有的基于线性预测残差四阶统计量峰度（Kurtosis）的方法具有更好的去混响效果,且对噪声具有更强的鲁棒性。     

Subjective preference tests for sound fields in concert halls simulated by the aid of a computer

In the context of optimal acoustic design of concert halls, preference tests for simulated sound fields with various combinations of early discrete reflections and subsequent reverberation were conducted and the results compared with objective parameters. The results show that lateral early reflections which yield a small value of the interaural cross correlation give more preferred judgments than do non-lateral ones. The most preferred initial time delay (or scale factor for the dimensions of concert halls) can be determined by the long-time autocorrelation function of a music motif and by the total amplitude of both early reflections and the subsequent reverberation. As a comprehensive design concept, an “overall preference” for listeners is introduced here from the preference results.     

Fast estimation of speech transmission index using the reverberation time

The paper presents the function of STI in the domain of reverberation time. Through the application of the said function, we can quickly estimate the speech transmission index, knowing only the time of room reverberation. For that purpose we applied a known method which consists in physical estimation of speech intelligibility basing on the modulation transfer function (MTF) determined in a room. Then, the STI was described using a logarithmic function whereof argument was the room reverberation time. To verify the model, reverberation times of six rooms were measured. The selected rooms were very different deliberately. They had different cubature and shape. The selection included a small cuboid, lecture halls and a church. Then, the same rooms were modeled in the ODEON version 11.23 and their reverberation times were determined. Furthermore, the STI was determined in the ODEON and then compared with the reverberation time obtained in effect of fast estimation. The statistical verification with the use of correlation index and regression equation has demonstrated that the fast estimation yields results close to those obtained in the computer simulation in ODEON. We obtained the correlation index at the level close to 1. Furthermore, the test probability at the level lower than 0.05 bespeaks of a statistically significant linear relation for the confidence level of 95%.     

球形传声器阵列下基于主导声源检测MUSIC群时延算法的多声源定位*

针对混响环境中,多径效应、散射、衍射等原因导致声源定位失败或分辨能力不足的现象,提出一种基于主导声源检测MUSIC群时延的邻近多声源定位方法。该方法采用球形传声器阵列,相比平面阵列可以捕获3D声场信息,利用球谐域下信号的频率分量与角度分量解耦的优势,从而可直接利用频率平滑技术处理宽带语声信号而不需要构造聚焦矩阵,并在球谐域下通过设置阈值对一组时频段进行主导声源检测,从而选择出包含直达声的一组时频块来构造MUSIC群时延空间谱。上述举措在提升波达方向估计在高混响环境下定位鲁棒性的同时,也提高了多个邻近声源的分辨能力。仿真实验结果表明,所提出的主导声源检测MUSIC群时延算法,在高混响和低信噪比条件下,仍具有更好的定位精度与更优的邻近多声源分辨效果。     

English consonant recognition in noise and in reverberation by Japanese and American listeners

English consonant recognition in undegraded and degraded listening conditions was compared for listeners whose primary language was either Japanese or American English. There were ten subjects in each of the two groups, termed the non-native (Japanese) and the native (American) subjects, respectively. The Modified Rhyme Test was degraded either by a babble of voices (S/N = -3 dB) or by a room reverberation (reverberation time, T = 1.2 s). The Japanese subjects performed at a lower level than the American subjects in both noise and reverberation, although the performance difference in the undegraded, quiet condition was relatively small. There was no difference between the scores obtained in noise and in reverberation for either group. A limited-error analysis revealed some differences in type of errors for the groups of listeners. Implications of the results are discussed in terms of the effects of degraded listening conditions on non-native listeners' speech perception.     

混响室内加载物损耗特性试验研究北大核心CSCD

为研究混响室加载效应,首先分析了混响室内各损耗途径,得出加载损耗是混响室测试过程中唯一人为可控的损耗路径。构建了常见的5种不同测试场景,利用时域法分别对这5种测试场景条件下的混响室品质因数进行测试并进行分析。结果表明,金属天线支架造成的加载效应最小,非金属天线支架会对混响室造成明显加载,降低混响室的品质因数,且随着非金属天线支架数量的增多,这种效应会愈发明显。此外,对加载物的平均吸收截面进行了研究,将混响室内所有加载物视为一个加载吸收截面,得到金属天线支架的吸收截面最小,非金属天线支架的加载吸收截面有明显增加。     

Reverberation time measurements in non-diffuse acoustic field by the modal reverberation time

The increasing presence of low frequency sources and the lack of acoustic standard measurement procedures make the extension of reverberation time measurements to frequencies below 100 Hz necessary. In typical ordinary rooms with volumes between 30 m³ and 200 m³ the sound field is non-diffuse at such low frequencies, entailing inhomogeneities in space and frequency domains. Presence of standing waves is also the main cause of bad quality of listening in terms of clarity and rumble effects. Since standard measurements according to ISO 3382 fail to achieve accurate and precise values in third octave bands due to non-linear decays caused by room modes, a new approach based on reverberation time measurements of single resonant frequencies (the modal reverberation time) has been introduced. From background theory, due to the intrinsic relation between modal decays and half bandwidth of resonant frequencies, two measurement methods have been proposed together with proper measurement procedures: a direct method based on interrupted source signal method, and an indirect method based on half bandwidth measurements. With microphones placed at corners of rectangular rooms in order to detect all modes and maximize SNRs, different source signals were tested. Anti-resonant sine waves and sweep signal turned out to be the most suitable for direct and indirect measurement methods respectively. From spatial measurements in an empty rectangular test room, comparison between direct and indirect methods showed good and significant agreements. This is the first experimental validation of the relation between resonant half bandwidth and modal reverberation time. Furthermore, comparisons between means and standard deviations of modal reverberation times and standard reverberation times in third octave bands confirm the inadequacy of standard procedure to get accurate and precise values at low frequencies with respect to the modal approach. Modal reverberation time measurements applied to furnished ordinary rooms confirm previous results in the limit of modal sound field: for highly damped modes due to furniture or acoustic treatment, the indirect method is not applicable due to strong suppression of modes and the consequent deviation of the acoustic field from a non-diffuse condition to a damped modal condition, while standard reverberation times align with direct method values. In the future, further investigations will be necessary in different rooms to improve uncertainty evaluation.     

利用正弦调频信号的宽带速度敏感特性抑制混响

有源声呐探测水中低速目标时,混响与目标回波的频率接近,目标回波与混响分离困难.根据运动目标与产生混响的散射体在速度域的差异,利用正弦调频信号(SFM)的速度敏感特性实现目标回波与混响的有效分离.推导了 SFM信号宽带混响抑制能力与速度分辨模糊之间的约束关系,建立了波形优化设计的搜索模型.通过多普勒滤波处理将数据从频率域...     

Identification of vowels in quiet, noise, and reverberation: relationships with age and hearing loss

Vowel identification in quiet, noise, and reverberation was tested with 40 subjects who varied in age and hearing level. Stimuli were 15 English vowels spoken in a (b-t) context in a carrier sentence, which were degraded by reverberation or noise (a babble of 12 voices). Vowel identification scores were correlated with various measures of hearing loss and with age. The mean of four hearing levels at 0.5, 1, 2, and 4 kHz, termed HTL4, produced the highest correlation coefficients in all three listening conditions. The correlation with age was smaller than with HTL4 and significant only for the degraded vowels. Further analyses were performed for subjects assigned to four groups on the basis of the amount of hearing loss. In noise, performance of all four groups was significantly different, whereas, in both quiet and reverberation, only the group with the greatest hearing loss performed differently from the other groups. The relationship among hearing loss, age, and number and type of errors is discussed in light of acoustic cues available for vowel identification.     

一种混响背景下的自适应动目标检测方法

本文提出了一种混响和噪声干扰下动目标检测的自适应方法,其结构为自适应混响抵消器（ARC）加推广的自适应相干累积器（GACI）。用自适应混响抵消实现干扰背景的预白化,用推广的自适应相干累积实现匹配滤波的功能。该方法不需要混响干扰的先验知识,也不需要知道信号参量,就可以实现混响干扰背景下动目标的检测。仿真和试验表明,其具有良好的动目标检测性能,且具有很好的海洋信道适应能力。