头相关传输函数幅度谱的听觉空间分辨阈值的分析

提出一种分析头相关传输函数(head-related transfer function,HRTF)幅度谱的听觉空间分辨阈值模型。采用数值计算得到的高空间分辨率HRTF数据,计算了声源空间位置变化引起的HRTF幅度谱的变化,进一步利用Moore响度模型分析双耳响度级差、双耳响度级谱和总响度级等三个听觉感知量的变化。根据现有的3个听觉感知量最小可察觉差异,模型利用双耳响度级差和双耳响度级谱的变化得到的估计结果与心理声学实验一致,因此是一种有效预测听觉空间分辨阈值的方法,可用于为简化虚拟听觉信号处理和数据储存。      

头相关传输函数幅度谱的听觉空间分辨阈值的分析

提出一种分析头相关传输函数(head-related transfer function,HRTF)幅度谱的听觉空间分辨阈值模型。采用数值计算得到的高空间分辨率HRTF数据,计算了声源空间位置变化引起的HRTF幅度谱的变化,进一步利用Moore响度模型分析双耳响度级差、双耳响度级谱和总响度级等三个听觉感知量的变化。根据现有的3个听觉感知量最小可察觉差异,模型利用双耳响度级差和双耳响度级谱的变化得到的估计结果与心理声学实验一致,因此是一种有效预测听觉空间分辨阈值的方法,可用于为简化虚拟听觉信号处理和数据储存。     

采用生理响度感知机制的车内噪声声品质预测

现有车内噪声声品质预测的响度计算中没有考虑真实人耳生理解剖结构的传声特性,因此提出了一种基于生理响度感知模型的车内噪声声品质预估方法。首先,采集两款轿车的车内噪声样本,并通过主观评价试验得到车内噪声的主观评价烦恼度。之后,整合中耳集总参数模型与耳蜗传输线模型,构建生理响度模型。然后,以生理响度模型的响度计算值为主要参数,结合尖锐度、粗糙度与车内噪声的主观评价值,通过TabNet模型构建了车辆声品质预测模型。最终,对比分析了所构建声品质模型与基于现有标准响度模型所构建的声品质模型的预测效果。结果表明,采用生理响度模型的声品质预测平均误差百分比仅有4.73%,优于采用Moore响度(6.13%)与Zwicker响度(6.94%)的声品质预测结果。此外,所构建的TabNet声品质预测模型的平均误差百分比也低于基于BP神经网络模型的平均误差百分比(7.60%)。采用生理响度模型的TabNet声品质预测能够提高车内噪声声品质客观评价的准确率。     

高密度氦状态方程的分子动力学模拟研究

 用分子动力学模拟和与固氦实验等温线比较的方法,确定了高密度氦指数6势函数中劲度系数α的优选值为12.7。然后我们用这个新的α值计算了fcc固氦的状态方程及其径向分布函数,发现当把ρ限定为1.60 g/cm³时,其径向分布函数的第二个峰将在2 000 K到3 040 K区间消失,表明此时固氦的长程有序性降低,或者说发生了固-液相变过程。     

在CP/MAS条件下交联聚甲基丙烯酸甲酯中α-甲基的~(13)C自旋-晶格弛豫(英文)

根据不同的跃迁运动和自由扩散运动模型导出了魔角旋转条件下的平均谱密度函数。从CP/MAS谱计算了样品中交联剂DVB的含量。依据实验测得的T_1值计算了一系列用DVB交联的聚甲基丙烯酸甲酯中x-甲基的转动相关时间以及扩散系数。结果表明:(1)随交联剂DVB含量的增加,相关时间增加,而扩散系数下降;(2)x-甲基的转动活化能与交联剂DVB无关,并且小于从介电和力学松弛所得的值。     

O2分子激发态a1△g和b1∑+g态的分析势能函数

以aug-co-pVQZ,cc-pV5Z,6-311++g(d,p)和6-311++g(3df,3pd)等为基函数,采用多组态相互作用(MRCI)方法对O2分子最低的两个激发态1△g和1∑+g的平衡结构、谐振频率和势能曲线进行了计算.并选用MurrelI-Sorbie势能函数对曲线进行拟合,利用拟合的参数值计算出了力常数和光谱数据.结果表明计算值与实验值符合较好.     

AlN,GaN和InN分子基态的结构和解析势能函数(英文)

采用密度泛函理论的B3LYP/6-311+G(3df)方法优化计算了A1N,GaN和InN分子基态的平衡结构、振动频率和离解能.根据原子分子反应静力学原理,导出了A1N,GaN和InN分子的合理离解极限,利用Murrell-Sorbie势能函数和从头算结果得到基态相应的解析势能函数并由光谱数据和解析势能函数的关系计算了基态的光谱数据(α_e,B_e,ω_e和ω_ex_e),计算结果与实验数据符合得相当好.     

金属钒弹性波速与热力学函数的理论计算

在全电子水平上,基于广义梯度近似(GGA)的密度泛函理论和全势能线性缀加平面波方法(FLAPW)计算了钒的晶格参数,弹性波速和格临爱森参数.在德拜模型的基础上,利用弹性波速方法和原子位移方法分别计算了钒的德拜频率,以及在标准条件下(298.15 K,1atm)的热容,熵等热力学函数,并与实验值进行了比较.     

HeH+分子X 1∑+、A 1∑+和a 3∑+态的势能函数与光谱常数研究

以Aug-cc-pVDZ、Aug-cc-pVTZ、Aug-cc-pVQZ和Aug-cc-pV5Z为基函数,分别采用组态相互作用(CI)和完全活性空间自洽场(CASSCF)方法对HeH+的X 1∑+、A 1∑+和a 3∑+的平衡结构、离解能、绝热跃迁能、谐振频率和势能曲线进行了计算。并选用Murrell-Sorbie势能函数对势能曲线进行拟合,利用拟合的参数值计算出了力常数和光谱数据。结果表明以Aug-cc-pV5Z为基函数,采用CI方法的计算值与实验值和其它理论结果吻合较好。     

用耦合簇理论及相关一致五重基研究SiH2(X1A1)自由基的解析势能函数

运用单双迭代三重激发耦合簇理论和相关一致五重基对SiH2的基态结构进行了优化,并在优化结构的基础上进行了离解能和振动频率的计算.结果表明:SiH2的基态为C2v结构,平衡核间距RSi-H=0.15163 nm,H-Si-H键的键角α=92.363°,离解能De(HSi-H)=3.2735 eV,频率ν1(a1)=1020.0095 cm -1,ν2(a1)=2074.8742cm-1,ν3(a1)=2076.4762cm-1.这些结果与实验值均较为相符.对H2的基态使用优选出的cc-pV6Z基组、对SiH的基态使用优选出的aug-cc-pV5Z基组进行几何构型与谐振频率的计算并进行单点能扫描,且将扫描结果拟合成了解析的Murrell-Sorbie函数.与实验结果及其他理论计算结果的比较表明,本文关于SiH自由基光谱常数(De,Re,ωe,Be,αe和ωeχe)的计算结果达到了很高的精度.采用多体项展式理论导出了SiH2(C2v,X1A1)自由基的解析势能函数,其等值势能图准确再现了它的离解能和平衡结构特征.同时还给出了SiH2(C2v,X1A1)自由基对称伸缩振动等值势能图中存在的两个对称鞍点,对应于SiH+H→SiH2反应,势垒高度为0.5084 eV.     

Relationships between arithmetic averages of sound pressure level calculated in octave bands and Zwicker’s loudness level

Previously it has been found through a series of psychoacoustical experiments that the arithmetic average of sound pressure level calculated in octave bands is a good estimator of loudness for various kinds of environmental noise. Remarkably, the arithmetic average of sound pressure level in octave bands from 63 Hz to 4 kHz, L_m,1/1(63-4k), strongly correlates with the loudness level specified in ISO 532B, LL(Z), as well as with loudness assessment. To investigate this relationship further, a numerical study has been carried out based on Zwicker’s loudness model. As a result, practical expressions to estimate the loudness levels of general environmental noises from the sound pressure levels in octave bands from 63 Hz or 125 Hz to 4 kHz are proposed.     

Modeling binaural loudness

A survey of data on the perception of binaurally presented sounds indicates that loudness summation across ears is less than perfect; a diotic sound is less than twice as loud as the same sound presented monaurally. The loudness model proposed by Moore et al. [J. Audio Eng. Soc. 45, 224-240 (1997)] determines the loudness of binaural stimuli by a simple summation of loudness across ears. It is described here how the model can be modified so as to give more accurate predictions of the loudness of binaurally presented sounds, including cases where the sounds at the two ears differ in level, frequency or both. The modification is based on the idea that there are inhibitory interactions between the internal representations of the signals at the two ears, such that a signal at the left ear inhibits (reduces) the loudness evoked by a signal at the right ear, and vice versa. The inhibition is assumed to spread across frequency channels. The modified model gives reasonably accurate predictions of a variety of data on the loudness of binaural stimuli, including data obtained using loudness scaling and loudness matching procedures.     

Acoustic and Perceptual Analyses of Brazilian Male Actors' and Nonactors' Voices: Long-term Average Spectrum and the “Actor's Formant”

SUMMARY: This study investigates the possible differences between actors' and nonactors' vocal projection strategies using acoustic and perceptual analyses. A total of 11 male actors and 10 male nonactors volunteered as subjects, reading an extended text sample in habitual, moderate, and loud levels. The samples were analyzed for sound pressure level (SPL), alpha ratio (difference between the average SPL of the 1-5kHz region and the average SPL of the 50Hz-1kHz region), fundamental frequency (F0), and long-term average spectrum (LTAS). Through LTAS, the mean frequency of the first formant (F1) range, the mean frequency of the "actor's formant," the level differences between the F1 frequency region and the F0 region (L1-L0), and the level differences between the strongest peak at 0-1kHz and that at 3-4kHz were measured. Eight voice specialists evaluated perceptually the degree of projection, loudness, and tension in the samples. The actors had a greater alpha ratio, stronger level of the "actor's formant" range, and a higher degree of perceived projection and loudness in all loudness levels. SPL, however, did not differ significantly between the actors and nonactors, and no differences were found in the mean formant frequencies ranges. The alpha ratio and the relative level of the "actor's formant" range seemed to be related to the degree of perceived loudness. From the physiological point of view, a more favorable glottal setting, providing a higher glottal closing speed, may be characteristic of these actors' projected voices. So, the projected voices, in this group of actors, were more related to the glottic source than to the resonance of the vocal tract.     

Further evaluation of a model of loudness perception applied to cochlear hearing loss.

This paper describes further tests of a model for loudness perception in people with cochlear hearing loss. It is assumed that the hearing loss (the elevation in absolute threshold) at each audiometric frequency can be partitioned into a loss due to damage to outer hair cells (OHCs) and a loss due to damage to inner hair cells (IHCs) and/or neurons. The former affects primarily the active mechanism that amplifies the basilar membrane (BM) response to weak sounds. It is modeled by increasing the excitation level required for threshold, which results in a steeper growth of specific loudness with increasing excitation level. Loss of frequency selectivity, which results in broader excitation patterns, is also assumed to be directly related to the OHC loss. IHC damage is modeled by an attenuation of the calculated excitation level at each frequency. The model also allows for the possibility of complete loss of IHCs or functional neurons at certain places within the cochlea ("dead" regions). The parameters of the model (OHC loss at each audiometric frequency, plus frequency limits of the dead regions) were determined for three subjects with unilateral cochlear hearing loss, using data on loudness matches between sinusoids presented alternately to their two ears. Further experiments used bands of noise that were either 1-equivalent rectangular bandwidth (ERB) wide or 6-ERBs wide, centered at 1 kHz. Subjects made loudness matches for these bands of noise both within ears and across ears. The model was reasonably accurate in predicting the results of these matches without any further adjustment of the parameters.     

Induced loudness reduction as a function of exposure time and signal frequency

Induced loudness reduction (ILR) is the decline in the loudness of a weaker tone induced by a preceding stronger tone. In this study we investigate how ILR depends on exposure time and signal frequency. For 12 listeners, successive magnitude estimation was used to measure the loudness of 70-dB-SPL test tones, presented with and without preceding 80-dB-SPL inducer tones at the same frequency. Experiment 1 measured the evolution of ILR over time at 0.5 kHz. The results suggest that ILR may begin after a single inducer presentation, and increases over at least 2 to 3 min as the inducer and test tones are repeated every few seconds. Following the cessation of the inducer, the recovery of loudness is slow and still incomplete after 1 min. Experiment 2 extended the measurements to additional signal frequencies. The results show that the amount of ILR and its evolution over time are approximately the same at frequencies from 0.5 to 8 kHz. Similarly, loudness matching showed no effect of frequency on ILR, which averaged 8.2 dB. These findings, together with previously noted similarities among ILR, ipsilaterally induced loudness adaptation, and temporary loudness shift, indicate that loudness reduction induced by stronger sounds is a very common phenomenon.     

Psychometric functions for gap detection in a yes-no procedure

To examine models of temporal resolution and to investigate the decision processes underlying the detection of a brief pause in a bandpass noise, psychometric functions for gap detection were measured at octave frequencies from 0.25 to 8 kHz. Three normal listeners were tested using a constant-stimulus procedure with a cued Yes-No paradigm. The Minimum Detectable Gap (MDG) estimated from the midpoint of the psychometric functions decreased systematically with increasing frequency. The slopes of the psychometric functions generally increased as the test frequency increased up to 2 kHz, but remained constant at the higher frequencies. Two models were investigated: an energy-detector model and a loudness-detector model. Both consisted of auditory filtering, a nonlinearity, and short-term integration. In the energy-detector model, the nonlinearity was a square law. In the loudness-detector model, it was a compressive power law. Using the usual Gaussian approximations, the energy-detector model fails at low frequencies because the probability distributions of short-term energy differ from Gaussian distributions. The probability distributions of short-term loudness closely follow Gaussian distributions. The loudness-detector model predicts the frequency dependence of the MDG quite accurately, except at 0.25 kHz. It also predicts psychometric functions that resemble the data at low frequencies, but the predicted slopes increase much less with frequency than the measured slopes. This result may indicate that the onset response to the trailing marker of the gap provides an important cue for detection of gaps with durations exceeding the MDG.     

Temporal integration of loudness in listeners with hearing losses of primarily cochlear origin.

To investigate how hearing loss of primarily cochlear origin affects the loudness of brief tones, loudness matches between 5- and 200-ms tones were obtained as a function of level for 15 listeners with cochlear impairments and for seven age-matched controls. Three frequencies, usually 0.5, 1, and 4 kHz, were tested in each listener using a two-interval, two--alternative forced--choice (2I, 2AFC) paradigm with a roving-level, up-down adaptive procedure. Results for the normal listeners generally were consistent with published data [e.g., Florentine et al., J. Acoust Soc. Am. 99, 1633-1644 (1996)]. The amount of temporal integration--defined as the level difference between equally loud short and long tones--varied nonmonotonically with level and was largest at moderate levels. No consistent effect of frequency was apparent. The impaired listeners varied widely, but most showed a clear effect of level on the amount of temporal integration. Overall, their results appear consistent with expectations based on knowledge of the general properties of their loudness-growth functions and the equal-loudness-ratio hypothesis, which states that the loudness ratio between equal-SPL long and brief tones is the same at all SPLs. The impaired listeners' amounts of temporal integration at high SPLs often were larger than normal, although it was reduced near threshold. When evaluated at equal SLs, the amount of temporal integration well above threshold usually was in the low end of the normal range. Two listeners with abrupt high-frequency hearing losses (slopes > 50 dB/octave) showed larger-than-normal maximal amounts of temporal integration (40 to 50 dB). This finding is consistent with the shallow loudness functions predicted by our excitation-pattern model for impaired listeners [Florentine et al., in Modeling Sensorineural Hearing Loss, edited by W. Jesteadt (Erlbaum, Mahwah, NJ, 1997), pp. 187-198]. Loudness functions derived from impaired listeners' temporal-integration functions indicate that restoration of loudness in listeners with cochlear hearing loss usually will require the same gain whether the sound is short or long.     

Subjective loudness level measurements and equal loudness contours in a bottlenose dolphin (Tursiops truncatus)

Loudness level measurements in human listeners are straightforward; however, it is difficult to convey the concepts of loudness matching or loudness comparison to (non-human) animals. For this reason, prior studies have relied upon objective measurements, such as response latency, to estimate equal loudness contours in animals. In this study, a bottlenose dolphin was trained to perform a loudness comparison test, where the listener indicates which of two sequential tones is louder. To enable reward of the dolphin, most trials featured tones with identical or similar frequencies, but relatively large sound pressure level differences, so that the loudness relationship was known. A relatively small percentage of trials were "probe" trials, with tone pairs whose loudness relationship was not known. Responses to the probe trials were used to construct psychometric functions describing the loudness relationship between a tone at a particular frequency and sound pressure level and that of a reference tone at 10 kHz with a sound pressure level of 90, 105, or 115 dB re 1 μPa. The loudness relationships were then used to construct equal loudness contours and auditory weighting functions that can be used to predict the frequency-dependent effects of noise on odontocetes.     

Objective estimation of loudness growth in hearing-impaired listeners

A methodology for the estimation of individual loudness growth functions using tone-burst otoacoustic emissions (TBOAEs) and tone-burst auditory brainstem responses (TBABRs) was proposed by Silva and Epstein [J. Acoust. Soc. Am. 127, 3629-3642 (2010)]. This work attempted to investigate the application of such technique to the more challenging cases of hearing-impaired listeners. The specific aims of this study were to (1) verify the accuracy of this technique with eight hearing-impaired listeners for 1- and 4-kHz tone-burst stimuli, (2) investigate the effect of residual noise levels from the TBABRs on the quality of the loudness growth estimation, and (3) provide a public dataset of physiological and psychoacoustical responses to a wide range of stimuli intensity. The results show that some of the physiological loudness growth estimates were within the mean-square-error range for standard psychoacoustical procedures, with closer agreement at 1 kHz. The median residual noise in the TBABRs was found to be related to the performance of the estimation, with some listeners showing strong improvements in the estimated loudness growth function when controlling for noise levels. This suggests that future studies using evoked potentials to estimate loudness growth should control for the estimated averaged residual noise levels of the TBABRs.