Encoding Sound Timbre in the Auditory System

The ability to localize a sound source is very important in our daily life, specifically to analyze auditory scenes in complex acoustic environments. The concept of minimum audible angle (MAA), which is defined as the smallest detectable difference between the incident directions of two sound sources, has been widely used in the research fields of auditory perception to measure localization ability. Measuring MAAs usually involves a reference sound source and either a large number of loudspeakers or a movable sound source in order to reproduce sound sources at a large number of predefined incident directions. However, existing MAA test systems are often cumbersome because they require a large number of loudspeakers or a mechanical rail slide and thus are expensive and inconvenient to use. This study investigates a novel MAA test method using virtual sound source synthesis and avoiding the problems with traditional methods. We compare the perceptual localization acuity of sound sources in two experimental designs: using the virtual presentation and real sound sources. The virtual sound source is reproduced through a pair of loudspeakers weighted by vector-based amplitude panning (VBAP). Results show that the average measured MAA at 0° azimuth is 1.1° and the average measured MAA at 90° azimuth is 3.1° in a virtual acoustic system, meanwhile the average measured MAA at 0° azimuth is about 1.2° and the average measured MAA at 90° azimuth is 3.3° when using the real sound sources. The measurements of the two methods have no significant difference. We conclude that the proposed MAA test system is a suitable alternative to more complicated and expensive setups.

The perception of basic emotional sounds, such as crying and laughter is associated with effective interpersonal communication. Difficulties with the perception and analysis of sounds that complicate understanding emotions at an early development age may contribute to communication deficits. This study focused on auditory nonverbal emotional perception including emotional vocalizations with opposite valences (crying and laughter) and neutral sound (phoneme "Pᴂ"). We conducted event-related potential analysis and compared peak alpha frequencies (PAFs) for different conditions in children with autism spectrum disorder (ASD) and typically developing (TD) children aged 4 to 6 years old (N = 25 for each group). Children with ASD had a higher amplitude of P100 and lower amplitude of N200 for all types of sounds and higher P270 in response to neutral phoneme. During the perception of emotional sounds, children with ASD demonstrated a single P270 electroencephalography (EEG) component instead of a P200-P300 complex specific to TD children. However, the most significant differences were associated with a response to emotional valences of stimuli. The EEG differences between crying and laughter were expressed as a lower amplitude of N400 and higher PAF for crying compared to laughter and were found only in TD children. Children with ASD have shown not just abnormal acoustical perception but altered emotional analysis of affective sounds as well.

The human brain has evolved to operate effectively in highly complex acoustic environments, segregating multiple sound sources into perceptually distinct auditory objects. A recent theory seeks to explain this ability by arguing that stream segregation occurs primarily due to the temporal coherence of the neural populations that encode the various features of an individual acoustic source. This theory has received support from both psychoacoustic and functional magnetic resonance imaging (fMRI) studies that use stimuli which model complex acoustic environments. Termed stochastic figure-ground (SFG) stimuli, they are composed of a "figure" and background that overlap in spectrotemporal space, such that the only way to segregate the figure is by computing the coherence of its frequency components over time. Here, we extend these psychoacoustic and fMRI findings by using the greater temporal resolution of electroencephalography to investigate the neural computation of temporal coherence. We present subjects with modified SFG stimuli wherein the temporal coherence of the figure is modulated stochastically over time, which allows us to use linear regression methods to extract a signature of the neural processing of this temporal coherence. We do this under both active and passive listening conditions. Our findings show an early effect of coherence during passive listening, lasting from ∼115 to 185 ms post-stimulus. When subjects are actively listening to the stimuli, these responses are larger and last longer, up to ∼265 ms. These findings provide evidence for early and preattentive neural computations of temporal coherence that are enhanced by active analysis of an auditory scene.

Binaural hearing and speech communication often take place in complex acoustic environments (CAEs) with a variety of interfering sounds and reverberation. For hearing research and the evaluation of hearing systems, virtual CAEs gained in interest to approach ecological validity. Here, the effects of complexity and visual representation of the CAEs on sound source localization, distance perception, loudness, speech intelligibility, and listening effort were investigated in a virtual audio-visual environment. The simulated sound field was rendered using a 3D, 86-channel loudspeaker array in combination with or without a stereoscopic head-mounted display (HMD) for the visual representation. The visual scenes consisted of a ring of eight virtual loudspeakers in an anechoic and an echoic condition with a reverberation time of about 1.5 s. Complexity of the environment was varied through the number of interfering sound sources, the receiver-target distance and by assessing all psychoacoustic measures after a single presentation or in consecutive measurements with one presentation for each measure. No significant effect of wearing an HMD was found. Reverberation, the number of maskers, and distance had significant effects on all psychoacoustic measures. These factors also degraded auditory cues relevant in speech communication, such as interaural coherence. There were significant, however, generally small deviations between assessment of all psychoacoustic measures after a single or consecutive presentation. The suggested setup is suited to be directly transferred to a corresponding real room, enabling a $1: 1$ comparison between real and virtual environments.

Masapollo, Polka, and Ménard (2017) recently reported a robust directional asymmetry in visual vowel perception: perceivers discriminated a change from an English /u/ viseme to a French /u/ viseme significantly better than a change in the reverse direction. This asymmetry parallels a frequent pattern in auditory vowel perception that points to a universal bias favoring “focal” vowels, whose distal articulatory gestures result in the convergence of adjacent formant frequencies. In the present study, we investigated how the integration of acoustic and visual speech cues influences these directional effects in bimodal vowel perception. In AX discrimination tests in which acoustic and visual cues were phonetically-incongruent, subjects showed an asymmetry, comparable to that found with unimodal stimuli, when there was an acoustic change in focalization, with visual focalization held constant. These findings indicate that acoustic cues are capable of inducing an asymmetry even when there is no cross-modal correspondence between the acoustic and visual channels. We are currently examining whether a similar asymmetry also emerges when there is a visual change in focalization, with acoustic focalization held constant. By comparing different types of audio-visual incongruence, we will be able to examine whether one sensory channel has more perceptual potency than the other.

The influence of the perceptual or fear learning on rats’ prepulse inhibition induced by changes in the correlation between two spatially separated noise sounds

Sound spectral analysis of prosthetic valvular clicks for diagnosis of thrombosed Björk-Shiley tilting standard disc valve prostheses

The regular behavior of sound sources helps us to make sense of the auditory environment. Regular patterns may, for instance, convey information on the identity of a sound source (such as the acoustic signature of a train moving on the rails). Yet typically, this signature overlaps in time with signals emitted from other sound sources. It is generally assumed that auditory regularity extraction cannot operate upon this mixture of signals because it only finds regularities between adjacent sounds. In this view, the auditory environment would be grouped into separate entities by means of readily available acoustic cues such as separation in frequency and location. Regularity extraction processes would then operate upon the resulting groups. Our new experimental evidence challenges this view. We presented two interleaved sound sequences which overlapped in frequency range and shared all acoustic parameters. The sequences only differed in their underlying regular patterns. We inserted deviants into one of the sequences to probe whether the regularity was extracted. In the first experiment, we found that these deviants elicited the mismatch negativity (MMN) component. Thus the auditory system was able to find the regularity between the non-adjacent sounds. Regularity extraction was not influenced by sequence cohesiveness as manipulated by the relative duration of tones and silent inter-tone-intervals. In the second experiment, we showed that a regularity connecting non-adjacent sounds was discovered only when the intervening sequence also contained a regular pattern, but not when the intervening sounds were randomly varying. This suggests that separate regular patterns are available to the auditory system as a cue for identifying signals coming from distinct sound sources. Thus auditory regularity extraction is not necessarily confined to a processing stage after initial sound grouping, but may precede grouping when other acoustic cues are unavailable.

This article presents common methods for sound source localization and separation, and their applications to robots.Sound source localization is an estimate of the location or direction of a sound source, whereas sound source separation extracts each sound source from a mixture of sound sources. Two approaches are possible for both technologies: binaural and microphone array processing. Sound source localization and separation have been widely studied in the fields of psychoacoustics, signal processing, and robotics. In binaural research, the human auditory capability is explored to solve both localization and separation problems. However, this approach is limited in terms of performance. Thus, microphone array processing is also being investigated as a primary topic in signal processing. Since robots are among the most promising applications of sound source localization and separation, robot audition is introduced and real‐time methods (such as the software platform for robot audition called Honda Research Institute Japan Audition for Robot with Kyoto University (HARK)) to deal with real‐world problems are explained.

The linearized inhomogeneous Euler (LIE) equation, originated from the generalized acoustic analogy theory, demonstrates that there is an exact analogy between the fluctuations occurring in any real flow and the linear inviscid fluctuations about an arbitrary flow produced by appropriate external stress and energy flux perturbations, which can be regarded as an input−output system. By employing a well-defined base flow, acoustic resolvent analysis can be performed based on the LIE equation, where the forcing mode corresponds to the sound source and the response mode to the far-field noise. According to such analyses, one can identify the nominally sound source structures that possess the highest acoustic radiation efficiency, which are optimally enhanced by the LIE system. However, a significant challenge arises from the rarity or even the nonexistence of these structures in actual flows. To address this, we have developed a constrained acoustic resolvent analysis with a physical low-dimensional forcing space, in which the forcing is space-time correlated. This approach can reveal the most significant part of sound source structures within flow fields, which is crucial for economical and efficient noise reduction control design. Then, sound noise analysis based on the constrained acoustic resolvent is applied in a subsonic turbulent jet. The dominant source mechanisms with high acoustic efficiency indicated by the optimal resolvent mode have been identified clearly. The leading forcing modes of constrained acoustic resolvent modes are capable of proposing a low-rank source model to recover the acoustic field. While the generalized acoustic analogy provided mathematical sources rather than true sound sources, we illustrated that the constrained acoustic resolvent is capable of distinguishing the ingredients with strong noise production in the far field and has the potential to develop a more accurate noise model as well as efficient noise control strategies in this framework.

When we designedly listen to a target, perhaps its signal is in the presence of competing signals or noise. An effective solution is to extract target signals from background noise and interference based on either location attributes or source attributes. Location attributes typically involve arrival angles and distance between listener and the sound source. Source attributes include characteristics that are specific to a signal, such as pitch, intensity, timbre, or statistical properties that differentiate signals. This paper describes a novel approach to analyze and comprehend real-world audition, and at the same time, it provides an effective way to auditory scene analysis. This idea and approach is named “auditory feature binding”. It can be used in machine perception, which has the ability of extract the focused target from its competing signals or noise. The elements and segments can be organized in the non-linear way to over-fly from the primary audition to senior audition perception. Besides, we will combine it with optic feature binding to realize cooperating management of audio-visual cross-modal signals which is emphasized in the National Science Fund of China Project “Research on Synergic Learning Algorithm of Audition-vision Cross-modal Coherence” (#60873139).

Electroacoustic music lacks a definitive vocabulary for describing its spatiality. Not only does it lack a vocabulary for describing the spatial attributes of individual sound sources, it lacks a vocabulary for describing how these attributes participate in artistic expression. Following work by Rumsey, the definition of spatial attributes is examined in the broader context of auditory scene analysis. A limited number of spatial attributes are found to be adequate to characterize the individual levels of organization nested within the auditory scene. These levels are then viewed in relationship to auditory spatial schemata, the recurrent patterns by which listeners understand the behavior of sound in space. In electroacoustic music the interrelationship of spatial attributes and spatial schemata is often engaged in a play of perceptual grouping that blurs and confounds distinctions like source and ensemble. Our ability to describe and categorize these complex interactions depends on having clear concepts and terminology.KeywordsSpatial AttributeSource ImagePerceptual GroupingSpatial SchemaConcert HallThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

We designed a computer-based respiratory sound analysis system to identify pediatric normal lung sound. To verify the validity of the computer-based respiratory sound analysis system. First we downloaded the standard lung sounds from the network database (website: http: //www.easyauscultation.com/lung-sounds-reference-guide) and recorded 3 samples of abnormal loud sound (rhonchi, wheeze and crackles) from three patients of The Department of Pediatrics, the First Affiliated Hospital of Xiamen University. We regarded such lung sounds as"reference lung sounds". The"test lung sounds"were recorded from 29 children form Kindergarten of Xiamen University. we recorded lung sound by portable electronic stethoscope and valid lung sounds were selected by manual identification. We introduced Mel-frequency cepstral coefficient (MFCC) to extract lung sound features and dynamic time warping (DTW) for signal classification. We had 39 standard lung sounds, recorded 58 test lung sounds. This computer-based respiratory sound analysis system was carried out in 58 lung sound recognition, correct identification of 52 times, error identification 6 times. Accuracy was 89.7%. Based on MFCC and DTW, our computer-based respiratory sound analysis system can effectively identify healthy lung sounds of children (accuracy can reach 89.7%), fully embodies the reliability of the lung sounds analysis system.

In the previous chapters I have mainly argued from within a Leibnizian perspective — first giving an outline of his account of (unconscious) perception, then relating it to some empirical findings, notably from auditory research, and finally explicating Leibniz’s account of the transition between unconscious and conscious states. In this chapter I attempt something complementary: I will introduce findings from auditory research in a systematic fashion to then relate them back to some of Leibniz’s claims. And since auditory research encompasses physiological as well as psychoacoustic studies and also correlations between physiological and psychological (behavioral) measures, Leibniz’s hypothesis of agreement will be scrutinized in this chapter as well.1

Recently, it has been demonstrated that men outperform women in spatial analysis of complex auditory scenes (Zündorf et al., 2011). The present study investigated the relation between the effects of ageing and sex on the spatial segregation of concurrent sounds in younger and middle-aged adults. The experimental design allowed simultaneous presentation of target and distractor sound sources at different locations. The resulting spatial "pulling" effect (that is, the bias of target localization toward that of the distractor) was used as a measure of performance. The pulling effect was stronger in middle-aged than younger subjects, and female than male subjects. This indicates lower performance of the middle-aged women in the sensory and attentional mechanisms extracting spatial information about the acoustic event of interest from the auditory scene than both younger and male subjects. Moreover, age-specific differences were most prominent for conditions with targets in right hemispace and distractors in left hemispace, suggesting bilateral asymmetries underlying the effect of ageing.