基于样本熵的听觉神经锁相机理的实验分析

锁相是指系统的响应与周期性刺激的特定相位同步的物理现象. 听觉神经的锁相对揭示人的听觉认知基本的神经机理及改善听觉感知有重要意义. 然而, 现有研究主要集中于心理物理方法和幅度谱分析, 不能有效区分包络响应和时域细节结构响应, 不能直观反映神经锁相. 本文主要利用拔靴法和离散傅里叶变换, 提出了基于样本熵的时域细节结构频率跟随响应(temporal-fine-structure-related frequency following response, FFR_T)的神经锁相值(phase locking value, PLV)计算方法, 用于分析神经物理实验数据. 两个脑电实验结果表明: FFR_T的PLV样本熵显著大于包络相关频率跟随响应(envelope-related frequency following response, FFR_E)的PLV, 且二者正交独立, 新方法能有效地分别反映听觉系统对包络和时间细节结构的锁相机理; 基频处的响应主要来源于FFR_E的锁相; 基频处, 不可分辨谐波成分包络的锁相能力优于对可分辨谐波; 基频缺失时, 畸变产物是不同的听觉神经通路的FFR_E的混合; 谐波处, FFR_E 集中于低频, FFR_T则集中于中、高频; 听觉神经元锁相能力与声源的频率可分辨性相关. FFR_T的PLV方法克服了现有FFR分析的局限性, 可用于深入研究听觉神经机理.     

重放自由场虚拟源距离信息的动态双耳Ambisonics方法

双耳重放的目标之一是在耳机重放中产生不同方向和距离的虚拟源感知。本文研究了动态双耳Ambisonics重放自由场虚拟源方向和距离信息的简化信号处理方法。该信号处理方法包括两步:第1步是基于目标声场的球谐函数分解,合成采用扬声器的近场Ambisonics重放中逐级重构目标声场的信号;第2步是采用虚拟扬声器重放的方法,用动态头相关函数滤波处理将Ambisonics的扬声器重放信号转换为双耳重放信号并用耳机重放。进一步研究了动态双耳Ambisonics的阶数对定位效果的影响,为简化信号处理提供依据。对重放产生的双耳声压分析表明,5阶动态双耳Ambisonics重放足以提供听觉方向定位和距离感知的重要信息。同时心理声学的实验结果表明,结合声源距离相关的响度因素,5阶动态双耳Ambisonics重放可产生不同方向和1.0 m以下不同近场距离的自由场虚拟源的听觉感知。本文的方法仅需要固定距离的48个均匀空间方向的远场非个性化HRTF处理,实现了信号处理的简化。      

基于低温超导量子干涉器件的脑 听觉激励磁场探测

本文利用磁屏蔽室和二阶轴向梯度计抑制环境磁场噪声, 建立了单通道脑磁探测系统, 并对不用声音频率下脑听觉激励磁场N100m响应进行了初步探测.结果显示, 1000 Hz音频和100 ms持续声音激励下, N100m峰值的典型强度约为0.4 pT.在低的声音频率激励下, N100m峰出现延时, 100 Hz 和1000 Hz之间的延时差别达到25 ms.相比于1 kHz特定频率的声音激励, 1—4 kHz 随机变频下的N100m峰幅度增强, 出现了数毫秒的延时.本研究为下一步利用软件梯度计进行多通道脑磁系统和听觉机理研究奠定了一定的基础.     

听觉基础研究的若干问题展望(2)

三、心理声学 当前心理声学研究的主要趋向是从以往纯音听觉的单因素研究转向具有频谱时间表征的复合声的多维研究。这个转变和生理声学的发展情况恰成有趣的对比。如上节所述,生理声学的近期进展是对Helmholtz为代表的传统耳蜗观念的突破。与此相反,心理声学的前进却不能不回到Helmholtz在其名著“乐音感觉:音乐理论的生理学基础”一书中提出的一个基本课题,即对音乐、言语这类复合声的知觉。自然,这并不是说心理声学应该迳直去研究音乐和言语,去取代音乐声学和言语声学。在     

基于双耳自相关函数的车辆噪声烦恼度研究

利用主成分分析法研究车辆噪声的双耳自相关函数(ACF)因子,确定了车辆噪声的原始听感与决定其代表性听觉感知属性的主导听感,并从各类听感描述因子与基本因子的变化规律角度,分析了车辆噪声主观烦恼度的形成机制.首先,依据车辆噪声的ACF特性,对既有ACF因子理论进行了补充和完善;提出平均起伏度(EMD)与包络衰减率(ESM)...     

Auditory filter based broadband MUSIC algorithm for sound source localization

Based on the analysis of the shortcomings of broadband MUSIC algorithm with short-time Fourier transform （SF-MUSIC） for sound source localization, a broadband MUSIC algorithm with auditory filter （AF-MUSIC） was proposed. The proposed algorithm first em- ploys auditory filter bank to decompose the signals received on the microphone array, and then locates the sound source with MUSIC algorithm over every frequency channel. At last, by combining with the subinterval frequency estimation, the final localization result is gained. Evaluations on the proposed algorithm prove that comparing with the SF-MUSIC algorithm, the AF-MUSIC algorithm decreases the average error of the estimation results with 2.5479 de- gree in different source conditions. The accuracy of sound source DOA estimation is enhanced effectively.     

声学随机共振实验

在特定的非线性系统中,噪声的存在能够增强信号的响应, 这种现象为随机共振. 本文实验通过观察噪声对听觉阈限的影响,使学生了解声学中的随机共振现象.     

Auditory place theory and frequency difference limen

It has been a barrier that the place code is far too coarse a mechanism to account for the finest frequency difference limen for place theory of hearing since it was proposed in 19th century. A place correlation model, which takes the energy distribution of a pure tone in neighboring bands of auditory filters into full account, was presented in this paper. The model based on the place theory and some experimental results of the psychophysical tuning curves of hearing can explain the finest difference limen for frequency (about 0.02 or 0.3% at 1000 Hz) easily. Using a standard 1/3 octave filter bank of which the relationship between the frequency of a input pure tone apart from the centre frequency of K-th filter band, Δf, and the output intensity difference between K-th and (K l)-th filters,ΔE, was established in order to show the fine frequency detection ability of the filter bank. This model can also be used to abstract the fundamental frequency of speech and to measure the frequency of pure tone precisely.     

Frequency Selectivity Behaviour in the Auditory Midbrain： Implications of Model Study

By numerical simulations on frequency dependence of the spiking threshold, i.e. on the critical amplitude of periodic stimulus, for a neuron to fire, we find that bushy cells in the cochlear nuclear exhibit frequency selec- tivity behaviour. However, the selective frequency band of a bushy cell is far away from that of the preferred spectral range in human and mammal auditory perception. The mechanism underlying this neural activity is also discussed. Further studies show that the ion channel densities have little impact on the selective frequency band of bushy cells. These findings suggest that the neuronal behaviour of frequency selectivity in bushy cells at both the single cell and population levels may be not functionally relevant to frequency discrimination. Our results may reveal a neural hint to the reconsideration on the busily cell functional role in auditory information processing of sound frequency.