人类对超声的听觉感知及应用前景

本文对人类通过骨传导所产生的超声听觉感知，就以下四方面进行介绍：１．感知的方法、频率和强度范围；２．感知机理；３．可能的应用；４．值得研究的问题。     

骨导振子佩戴位置对重放声的影响*

骨导振子佩戴位置会影响骨传导声重放的性能,但已有研究还不够全面和完善。针对11名双耳听力正常的受试者,采取不同的骨导振子佩戴位置,对骨传导声重放在听力阈值、主观音质评价和语言清晰度3个方面进行了研究。实验结果表明不同的佩戴位置会影响骨传导声重放性能,髁骨位置在3个实验都表现最好,髁骨的听力阈值比乳突位置平均低8.7 dB,主观音质评价得分平均高乳突38.4分。该文的研究可为骨导振子佩戴位置的选择提供依据,并为声重放质量的改进提供参考。     

基于听觉感知的语音稀疏表示及压缩感知*

本文针对语音信号稀疏表示及压缩感知问题,将听觉感知引入稀疏系数筛选过程,用掩蔽阈值筛选重要系数,以得到更符合听觉感受的语音稀疏表示。通过对一帧浊音信号分别采用掩蔽阈值和能量阈值方法进行系数筛选对比实验,结果表明掩蔽阈值法具有更好的稀疏表示效果。为验证听觉感知对语音压缩感知性能的影响,与能量阈值法对照对测试语音进行压缩感知观测和重构,通过压缩比、信噪比、主观平均意见分等主客观指标评价其性能,结果表明,掩蔽阈值法可有效地提高压缩比且保证重构语音具有较高的主观听觉质量。     

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。      

语音中相位的听觉感知实验研究

人的听觉对语音信号中相位的感知比较迟钝,因而对语音信号进行处理和编码时常常不关心相位失真。实际上,相位失真到一定程度时会明显导致语音质量的下降。为了取得高质量的声码器,语音谱分量的相位信息是不能不考虑的。本文通过主观听觉测试实验研究了语音信号的短时Fourier变换相位谱对人的听觉感知的影响。测试结果表明: (1)如果完全舍弃原相位信息,则得到的重建语音含有很强的噪声且自然度很差; (2)不论舍弃高频段还是低频段的相位信息,均能导致听觉感知差异; (3)当相位的量阶小于π/7时,人的听觉系统将分辨不出重建语音和原始语音之间存在的差异.     

人耳辨识非语言声目标能力的实验研究

以主观听觉测试实验为手段,研究人耳听觉系统辨识能力与声音特性、评价主体训练程度及噪声干扰的关系.实验结果发现：人耳辨识声音能力主要由声信号的谱时结构决定,人耳对于谐音信号的辨识能力明显强于非谐音,对于稳态信号的辨识能力略强于瞬态信号;评价主体的训练可以提高辨识效果及准确性,但与声音特性密切相关;不同的噪声干扰对人耳目标辨识能力的影响主要取决于声音频谱结构;比对测听方式能提高非受训人员的辨识准确性,但不影响受训人员的辨识效果. 关键词： 听觉系统 主观听觉测试 目标辨识     

语后聋人工耳蜗使用者电刺激听觉部位音调感知研究

系统地研究了人工耳蜗植入者的电刺激听觉部位音调感知,全面地探讨了部位音调感知与人工耳蜗植入者言语识别和音乐感知的关系。4位成人语后聋人工耳蜗植入者参与了该研究。通过电极音调排序测试度量植入者的部位音调感知能力。言语能力测试和音乐音高分辨测试分别用米考察植入者的言语识别和音乐感知能力。结果显示,随着电极刺激部位从蜗尖移向蜗底,所有受试者均可获得从"低"到"高"的音调感知变化,但个体差异较大。受试者的言语识别结果与其电刺激听觉部位音调感知能力相关,但受到天花板效应影响,对应关系并不明显。受试者的音乐音高分辨成绩与其电刺激听觉部位音调感知能力呈较好的对应关系。结果表明,当前人工耳蜗声音编码策略所传递的声信号特征已可使植入者获得良好的言语识别效果;且安静环境下言语识别对植入者的部位音调感知能力要求不高。但当前的声音编码策略并未能有效对音乐信号进行编码;植入者在理解音乐这类复杂声信号时,其电刺激听觉部位音调感知能力一定程度决定了其听音效果。      

膜迷路积水对豚鼠听觉外周系统振动特性的影响

为探究梅尼埃病引起的膜迷路积水对豚鼠听觉系统振动特性的作用机制,通过药物注射建立了内耳膜迷路积水豚鼠模型模拟梅尼埃病病理,搭建了多普勒激光测振系统对健康和膜迷路积水豚鼠听觉系统的振动特性进行测试研究,得到了健康与膜迷路积水豚鼠的听觉系统振动特性,并通过对比明确了内耳膜迷路积水对豚鼠听觉系统振动特性的影响。实验结果表明,在测试频率范围内,离体豚鼠镫骨及圆窗膜的振动特性与活体豚鼠无明显差异,离体豚鼠听觉系统振动特性与输入声压无关,镫骨及圆窗膜的振动位移与输入声压具有明显的线性关系。膜迷路积水显著降低了豚鼠听觉系统镫骨及圆窗膜的振动幅度,在低频及高频区间尤为明显,在500 Hz处镫骨最高由11.64 nm降低至2.27 nm,圆窗膜由24.97 nm降低至5.05 nm。在10 kHz处,圆窗膜最高由0.45 nm降低至0.03 nm。同时膜迷路积水导致豚鼠耳蜗传递比普遍下降,最高在1 kHz和10 kHz处分别由2.82,2.91下降至1.46,0.28。      

《空间声原理》

正谢菠荪著科学出版社,北京,2019年6月,818页,定价:249元听觉是我们感知外界信息的重要途径之一。人的听觉中,除了对声音的响度、音调和音色等主观属性的感觉外,还包括对声音的空间听觉,也就是对声音空间属性或特性的感知。这赋予了我们的听觉系统在一定的条件下,可以对声源进行定位,可以产生对周围声学环境的空间印象的可能。空间声的目的是重放声场的空间信息,给倾听者产生特定的空间听觉事件或感知。近年来,其应用已由传统的影院和家用声重放等文化娱乐领域,拓展到听觉心理和生理、室内声学设计、通信、互联网与计算机、多媒体与虚拟现实、医学等科学研究及工程技术领域。可见应用价值之重要。     

旋转调制捷联惯导激光陀螺仪误差自补偿新方法

基于旋转调制的自补偿技术是进一步提高激光陀螺仪捷联惯导系统导航精度的有效方法。研究了旋转调制捷联惯导系统中的激光陀螺仪误差补偿方法。建立旋转式捷联惯导系统激光陀螺仪的误差传播方程,分析激光陀螺仪旋转误差效应及误差传播特性,在此基础上建立了调制策略编排目标函数;研究了双轴交替旋转调制模式下的调制策略编排方案,提出了一种改进的16次序双轴交替旋转调制方法,建立了基于双轴转动角速度的动态误差方程,实现了转动过程中激光陀螺仪的常值项误差、标度因数误差、安装误差的有效补偿,进一步抑制速度误差积累所引起的位置误差。仿真结果验证了该方法的有效性,提高了捷联惯导系统导航精度,可为旋转调制光学捷联惯导系统设计提供理论参考。     

Estimating bottlenose dolphin (Tursiops truncatus) hearing thresholds from single and multiple simultaneous auditory evoked potentials

Hearing thresholds were estimated in four bottlenose dolphins by measuring auditory evoked responses to single and multiple sinusoidal amplitude modulated tones. Subjects consisted of two males and two females with ages from 4 to 22 years. Testing was conducted in air using a "jawphone" transducer to couple sound into each subject's lower right jaw. Carrier frequencies ranged from 10 to 160 kHz in one-half octave steps. Amplitude modulated stimuli were presented individually and as the sum of four, five, and nine simultaneous tones with unique carrier and modulation frequencies. Evoked potentials were noninvasively recorded using surface electrodes embedded in silicon suction cups. The presence or absence of an evoked response at each modulation frequency was assessed by calculating the magnitude-squared coherence from the frequency spectra of the recorded sweeps. All subjects exhibited traditional "U-shaped" audiograms with upper cutoff frequencies above 113 kHz. The time required for threshold estimates ranged from 23 to 37 min for single stimuli to 5-9 min for nine simultaneous stimuli. Agreement between thresholds estimated from single stimuli and multiple, simultaneous stimuli was generally good, indicating that multiple stimuli may be used for quick hearing assessment when time is limited.     

Modulation detection for amplitude-modulated bone-conducted sounds with sinusoidal carriers in the high- and ultrasonic-frequency range

Ultrasonic vibration generates a sensation of sound via bone-conduction. This phenomenon is called bone-conducted ultrasonic (BCU) hearing. Complex sounds can also be perceived by amplitude-modulating a BCU stimulus (AM-BCU). The influence of the modulation frequency on the sensitivity to detecting amplitude modulation of sinusoidal carriers of 10, 20, and 30 kHz was examined to clarify the characteristics of the perception of amplitude modulation over the sonic or audio-frequency range and the ultrasonic range. In addition, the detection sensitivity for single-sideband modulation for a 20 kHz carrier was measured. Temporal modulation transfer functions (TMTFs) obtained at each carrier frequency suggest that the auditory system has the ability to process timing information in the envelopes of AM-BCUs at lower modulation frequencies, as is the case with audio-frequency sounds. The possible influence of peripheral filtering on the shape of the TMTF at higher frequencies was examined.     

Variation in the hearing sensitivity of a dolphin population determined through the use of evoked potential audiometry

A portable electrophysiological data collection system was used to assess hearing in a captive population of bottlenose dolphins by recording auditory evoked potentials (AEPs). The AEP system used a transducer embedded in a suction cup to deliver amplitude modulated tones to the dolphin through the lower jaw. Evoked potentials were recorded noninvasively using surface electrodes. Adaptive procedures allowed hearing thresholds to be estimated from 10 to 150 kHz in a single ear in about 45 min. Hearing thresholds were measured in 42 bottlenose dolphins (28 male, 14 female), ranging in age from 4 to 47 years. Variations in hearing sensitivity with age and sex followed patterns seen in humans and terrestrial mammals: generally, within the population there was a progressive loss of high frequency hearing with age and an earlier onset of hearing loss in males than in females. Hearing loss generally occurred between the ages of 20 and 30, and all animals over the age of 27 had some degree of hearing loss. Two dolphins with profound hearing loss were found within the population. Aberrant hearing patterns were observed in related dolphins suggesting genetic links to hearing ability may exist.     

Frequency discrimination for pulsed versus modulated tones

Estimates of frequency discrimination for pulsed modulated tones were obtained by 11 observers at 350, 500, 1000, 4000, and 8000 Hz. At low frequencies, frequency DL's are larger for modulated than for pulsed tones; at 8000 Hz the contrary was found. Frequency DL's (difference limens) determined by different methods and procedures differed by a factor up to four; extreme individual frequency DL's, however, by a factor up to 27.     

Assessing temporary threshold shift in a bottlenose dolphin (Tursiops truncatus) using multiple simultaneous auditory evoked potentials

Hearing sensitivity was measured in a bottlenose dolphin before and after exposure to an intense 20-kHz fatiguing tone in three different experiments. In each experiment, hearing was characterized using both the auditory steady-state response (ASSR) and behavioral methods. In experiments 1 and 2, ASSR stimuli consisted of seven frequency-modulated tones, each with a unique carrier and modulation frequency. The tones were simultaneously presented to the subject and the ASSR at each modulation rate measured to determine the effects of the sound exposure at the corresponding carrier frequency. In experiment 3 behavioral thresholds and ASSR input-output functions were measured at a single frequency before and after three exposures. Hearing loss was frequency-dependent, with the largest temporary threshold shifts occurring (in order) at 30, 40, and 20 kHz. ASSR threshold shifts reached 40-45 dB and were always larger than behavioral shifts (19-33 dB). The ASSR input-output functions were represented as the sum of two processes: a low threshold, saturating process and a higher threshold, linear process, that react and recover to fatigue at different rates. The loss of the near-threshold saturating process after exposure may explain the discrepancies between the ASSR and behavioral threshold shifts.     

Discriminating between coherent and incoherent frequency modulation of complex tones

A series of experiments measured the discrimination by human listeners of frequency-modulated complex tones which differed only in the coherence of frequency modulation (FM). For the coherently modulated tones all components were modulated by the same 5-Hz sinusoid, and by the same percentage of their starting frequencies, whereas for the incoherently modulated tones the modulation of one (target) component differed from that of the rest. When the 400-ms complex was composed of consecutive harmonics of a common fundamental, performance improved monotonically with increases in modulator delay, and was nearly perfect at the longest delays. When the complex was inharmonic, performance was near chance at all modular delays, both for component frequencies between 1500 and 2500 Hz, and for component frequencies between 400 and 800 Hz. It is argued that listeners detected incoherence in harmonic complexes by detecting the resulting mistuning of the target component. This conclusion was supported by the finding that listeners were usually at least as good at detecting a fixed mistuning of the center component of a harmonic complex as they were at detecting a modulator phase delay imposed on it. A final experiment, with a stimulus duration of 1 s and slower modulation rates, showed that listeners could detect incoherence for some inharmonic complexes. However, detection was worse than for harmonic complexes and was, it is argued, based on weak harmonicity cues. The results of all experiments point to the absence of an across-frequency mechanism specific to the detection of FM incoherence.     

Hearing thresholds for pure tones above 16 kHz

Hearing thresholds for pure tones between 16 and 30 kHz were measured by an adaptive method. The maximum presentation level at the entrance of the outer ear was about 110 dB SPL. To prevent the listeners from detecting subharmonic distortions in the lower frequencies, pink noise was presented as a masker. Even at 28 kHz, threshold values were obtained from 3 out of 32 ears. No thresholds were obtained for 30 kHz tone. Between 20 and 28 kHz, the threshold tended to increase rather gradually, whereas it increased abruptly between 16 and 20 kHz.     

Neural responses to the onset of voicing are unrelated to other measures of temporal resolution

Voice onset time (VOT) is a temporal cue that can distinguish consonants such as /d/ from /t/. It has previously been shown that neurons' responses to the onset of voicing are strongly dependent on their static spectral sensitivity. This study examined the relation between temporal resolution, determined from responses to sinusoidally amplitude-modulated (SAM) tones, and responses to syllables with different VOTs. Responses to syllables and SAM tones were obtained from low-frequency neurons in the inferior colliculus (IC) of the chinchilla. VOT and modulation period varied from 10 to 70 ms in 10-ms steps, and discharge rates elicited by stimuli whose amplitude envelopes were modulated over the same temporal interval were compared. Neurons that respond preferentially to syllables with particular VOTs might be expected to respond best to the SAM tones with comparable modulation periods. However, no consistent agreement between responses to VOT syllables and to SAM tones was obtained. These results confirm the previous suggestion that IC neurons' selectivity for VOT is determined by spectral rather than temporal sensitivity.     

New hearing threshold measurements for pure tones under free-field listening conditions.

Hearing thresholds for pure tones were measured under free-field listening conditions in the frequency range of 40 Hz-15 kHz. Results are consistent with the standard threshold specified in ISO 226 for frequencies up to 250 Hz, but a few dB below the ISO curve at higher frequencies. Thresholds are distributed normally on a logarithmic level scale with a standard deviation of approximately 5 dB. No significant differences between thresholds of male and female subjects were observed.     

Dolphin and sea lion auditory evoked potentials in response to single and multiple swept amplitude tones

Measurement of the auditory steady-state response (ASSR) is increasingly used to assess marine mammal hearing. These tests normally entail measuring the ASSR to a sequence of sinusoidally amplitude modulated tones, so that the ASSR amplitude function can be defined and the auditory threshold estimated. In this study, an alternative method was employed, where the ASSR was elicited by an amplitude modulated stimulus whose sound pressure level was slowly varied, or "swept," over a range of levels believed to bracket the threshold. The ASSR amplitude function was obtained by analyzing the resulting grand average evoked potential using a short-time Fourier transform. The suitability of this technique for hearing assessment of bottlenose dolphins and California sea lions was evaluated by comparing ASSR amplitude functions and thresholds obtained with swept amplitude and discrete, constant amplitude stimuli. When factors such as the number of simultaneous tones, the number of averages, and the frequency analysis window length were taken into account, the performance and time required for the swept-amplitude and discrete stimulus techniques were similar. The decision to use one technique over another depends on the relative importance of obtaining suprathreshold information versus the lowest possible thresholds.