Sound Source Distance Research Articles

Sound source localization based on sparse estimation and convex clustering

Sound source localization techniques in array signal processing have been interested for many years. A lot of direction-of-arrival (DOA) estimation methods have been proposed. Most of them use plane waves as model. On the other hand, 3D sound source localization techniques are important for many applications. They are required to estimate the DOA and the distance of sound sources. In the case of the techniques targeted to estimate the distances of sound sources, monopoles must be used for the model. The positions of monopoles are candidates for the sound source positions. However, it is difficult to handle a large number of monopoles placed at various distances. Moreover, it is difficult to decide the number of sound sources to be estimated from the candidates. The proposed method uses sparse estimation with a monopole dictionary in frequency domain, as is well known that the effectiveness of sparse representation for DOA estimation has been in late years. After the sparse estimation, the proposed method ...

Factors influencing auditory localization by moving listeners

Previous results have shown that observers who are walking at a constant pace on a treadmill are able to localize continuous sound sources and acquire and identify audiovisual targets more quickly than observers who are standing on a stationary platform, with no apparent loss in accuracy. In order to better understand the conditions where self-motion might enhance localization performance, a follow-on experiment was conducted that measured localization accuracy with sounds of three different durations (250 ms, 1000 ms, and continuous) under four different movement conditions (standing on a stationary platform, standing on a moving platform, walking on a treadmill at a self-paced rate, and walking on a treadmill at a constant rate). Localization accuracy was also measured both standing and walking when spatial cues were degraded by the use of a hearing protection device. As expected, the results suggest that short sounds are localized less accurately than long-duration sounds. However, preliminary results also suggest that walking at a constant pace may provide a greater benefit for localization than self-paced walking. The results are discussed in terms of the possible dynamic localization cues listeners might have access to when they are moving relative to the location of a distant sound source. [Work supported by MRMC Grant W81XWH-12-2-0068; The opinions presented are the private views of the authors and are not to be construed as official or as necessarily reflecting the views of the Department of Defense.]

Interactive Sound Propagation and Rendering for Large Multi-Source Scenes

We present an approach to generate plausible acoustic effects at interactive rates in large dynamic environments containing many sound sources. Our formulation combines listener-based backward ray tracing with sound source clustering and hybrid audio rendering to handle complex scenes. We present a new algorithm for dynamic late reverberation that performs high-order ray tracing from the listener against spherical sound sources. We achieve sublinear scaling with the number of sources by clustering distant sound sources and taking relative visibility into account. We also describe a hybrid convolution-based audio rendering technique that can process hundreds of thousands of sound paths at interactive rates. We demonstrate the performance on many indoor and outdoor scenes with up to 200 sound sources. In practice, our algorithm can compute more than 50 reflection orders at interactive rates on a multicore PC, and we observe a 5x speedup over prior geometric sound propagation algorithms.

Enhanced novelty detection in auditory scenes through adaptation of inhibition

Animals and humans must behave efficiently in acoustically rich environments, where few sound sources are of interest of many others that are considered background noise. How does the auditory system implement such robust processing is a topic of intense research. In this work I am interested in the neural mechanisms underlying detection of novel objects in auditory scenes, such as a novel sound source at a given location. It has been shown psycho-physically that the perception of a sound depends on the acoustical context in which it occurs. A basic example of such effect is called enhancement [1]. A harmonic complex (i.e. a series of tones at different frequencies) presented in isolation will be perceived as a single auditory object. If one tone is deleted from the complex (the conditioner) and then reintroduced (test), it will perceptually pop out as a separate sound object. To maximally induce enhancement in humans, the conditioner must have an energy notch in its spectrum with a preferred width of 0.6 octave. This effect originates in the central nervous system; neural correlate thereof were found in the cochlear nucleus, two synapses away from the cochlea [2]. The standard model explaining the emergence of auditory enhancement is based on the adaptation of wide-band inhibition inputs [1,2]: the increase in output rate due to a preceding conditioner comes from a decrease in activity of the wide-band inhibitory inputs, i.e. inhibition have adapted during the conditioner while narrow band excitation has not. In this study I seek to test functions of enhancement effects in realistic listening situations. In particular, I hypothesize that the enhancement of speech signals by realistic environments is a neural implementation of a novelty detector. I implemented on the Brian simulator and its auditory package [3] a model of the auditory periphery followed by a network of adapting spiking neurons [4] comprising feed forward excitation and inhibition. This network was first tuned to reproduce the basic enhancement effects reported physiologically. In order to mimic realistic listening conditions, sounds are filtered by realistic environmental processes prior to being fed to the model. In particular I'm interested in the filtering induced in sounds arriving at the ear by the listener's body and by the surrounding room. The head and the shoulder create reflections of the direct sound, resulting in notches in the high frequency sound spectrum, which depend on the sound source elevation [5]. Similarly, reflections from the ground and the walls of a room will induce notches in the low-frequency spectrum, which depend on the sound source azimuth and distance [6]. As spectral notches are critical in inducing auditory enhancement I show that if a novel sound is preceded by other sounds located at different positions, the detection of this novel sound will be enhanced. The present functional study of auditory enhancement suggests that such contextual effects could be critical for animal survival and for hearing in realistic conditions. The results show how simple neural mechanisms modulate a sensory pathway so that it adapts to its surrounding environment and suggest that bias in perception could have ecological advantages. The model could also inspire the design of speech processing devices in real environments.

Sound frequency-invariant neural coding of a frequency-dependent cue to sound source location.

The century-old duplex theory of sound localization posits that low- and high-frequency sounds are localized with two different acoustical cues, interaural time and level differences (ITDs and ILDs), respectively. While behavioral studies in humans and behavioral and neurophysiological studies in a variety of animal models have largely supported the duplex theory, behavioral sensitivity to ILD is curiously invariant across the audible spectrum. Here we demonstrate that auditory midbrain neurons in the chinchilla (Chinchilla lanigera) also encode ILDs in a frequency-invariant manner, efficiently representing the full range of acoustical ILDs experienced as a joint function of sound source frequency, azimuth, and distance. We further show, using Fisher information, that nominal "low-frequency" and "high-frequency" ILD-sensitive neural populations can discriminate ILD with similar acuity, yielding neural ILD discrimination thresholds for near-midline sources comparable to behavioral discrimination thresholds estimated for chinchillas. These findings thus suggest a revision to the duplex theory and reinforce ecological and efficiency principles that hold that neural systems have evolved to encode the spectrum of biologically relevant sensory signals to which they are naturally exposed.

Auditory distance coding in rabbit midbrain neurons and human perception: monaural amplitude modulation depth as a cue.

Mechanisms underlying sound source distance localization are not well understood. Here we tested the hypothesis that a novel mechanism can create monaural distance sensitivity: a combination of auditory midbrain neurons' sensitivity to amplitude modulation (AM) depth and distance-dependent loss of AM in reverberation. We used virtual auditory space (VAS) methods for sounds at various distances in anechoic and reverberant environments. Stimulus level was constant across distance. With increasing modulation depth, some rabbit inferior colliculus neurons increased firing rates whereas others decreased. These neurons exhibited monotonic relationships between firing rates and distance for monaurally presented noise when two conditions were met: (1) the sound had AM, and (2) the environment was reverberant. The firing rates as a function of distance remained approximately constant without AM in either environment and, in an anechoic condition, even with AM. We corroborated this finding by reproducing the distance sensitivity using a neural model. We also conducted a human psychophysical study using similar methods. Normal-hearing listeners reported perceived distance in response to monaural 1 octave 4 kHz noise source sounds presented at distances of 35-200 cm. We found parallels between the rabbit neural and human responses. In both, sound distance could be discriminated only if the monaural sound in reverberation had AM. These observations support the hypothesis. When other cues are available (e.g., in binaural hearing), how much the auditory system actually uses the AM as a distance cue remains to be determined.

Auditory/visual distance perception

A considerable body of research suggests that the perception of sound source distance exhibits systematic biases. The distances of far sources are progressively underestimated, but near sources are overestimated. Such biases are typically not observed in vision, where perceived distance is found to be highly accurate under natural viewing conditions in which a variety of visual distance cues are available. Relatively little is known about how distance information from both auditory and visual modalities is combined in the perception of distance, however. This is surprising, given that auditory/visual aspects of directional perception have been extensively studied, primarily in relation to the “ventriloquist effect.” Here, two recent experiments on auditory/visual distance perception are summarized. The results from both suggest that not only is perceived distance less accurate in the auditory modality than in vision, but it is also considerably less precise. These results explain why visual information, when available, appears to dominate auditory information in the perception of distance. [Work supported by NEI.]

Near-field discrimination of sound source distance in the rabbit.

The acoustical cues and physiological processing mechanisms underlying the perception of the distance of sound sources are not well understood. To understand the relation between physiology and behavior, a first step is to use an animal model to study distance sensitivity. The goal of these experiments was to establish the capacity of the Dutch-belted rabbit to discriminate between sound sources at two distances. Trains of noise bursts were presented from speakers that were located either directly in front of the rabbit or at a 45 ° angle in azimuth. The reference speaker was positioned at distances of 20, 40, and 60 cm from the subject, and the more distant test speaker was systematically moved to determine the smallest difference in distance that could be reliably discriminated by the subject. Noise stimuli had one of three bandwidths: wideband (0.1-10 kHz), low-pass (0.1-3 kHz), or high-pass (3-10 kHz). The mean stimulus level was 60 dB sound pressure level (SPL) at the location of the rabbit's head, and the level was roved over a 12-dB range from trial to trial to reduce the availability of level cues. An operant one-interval two-alternative non-forced choice task was used, with a blocked two-down-one-up tracking procedure to determine the distance discriminability. Rabbits were consistently able to discriminate two distances when they were sufficiently separated. Sensitivity was better when the reference distance was 60 cm at either azimuth (distance ratio = 1.5) and was worse when the reference distance was 20 cm (distance ratio = 2.4 at 0 ° and 1.75 at 45 °).

On distance dependence of pinna spectral patterns in head-related transfer functions.

The aim of this letter is to address a little understood question in sound source localization: Can the distance of a near sound source affect our own perception of its elevation? The issue is studied by means of an objective analysis of a database of distance-dependent head-related transfer functions (HRTFs) of a KEMAR (Knowles Electronic Manikin for Acoustic Research) mannequin with different pinnae on a dense spatial grid. Iso-directional HRTFs are compared through spectral error metrics; results indicate significant distance-dependent HRTF modifications due to the pinna occur when the source is close to the interaural axis.

The role of amplitude modulation in auditory distance perception

The ratio of direct to reverberant sound energy (D/R) has been shown to be a primary acoustic cue to perceived sound source distance. Because it is unclear exactly how D/R might be encoded in the auditory system, a variety of more physiologically plausible correlates to D/R have been identified, including: spectral variance, interaural correlation, and temporal cues. Here, following recent neural work by Kuwada and Kim [ARO (2014)], we describe a new correlate to D/R and perceived distance related to the amplitude modulation (AM) depth of the signal at the listener's location. This cue is caused by the change in the modulation transfer characteristics of the room as a function of source distance. Results from an apparent distance estimation task confirm the efficacy of this AM depth cue in a reverberant soundfield (approximate broadband T60 = 3 s), when level cues are made ineffective. Distance estimates were found to be more accurate when the source signal (1-octave band of noise centered at 4 kHz) had AM (32 Hz, 100% depth), and this facilitation was only observed in reverberation. The facilitation was most evident for monaural input, indicating that the AM depth cue is likely processed monaurally.

Light Source Distance Affects Perceived Audiovisual Simultaneity

Distance of sound and light sources affects the proximal stimulation and some of these changes can influence the perceived timing of stimuli. Sound source distance causes attenuation and transmission delay. Light source distance causes decreased retinal size and lower stimulus energy. These modifications could have opposite influences on the perception of simultaneity, however it is often assumed that the effect of distance on simultaneity perception is primarily due to the distance of the sound source. Here we compare the magnitude of the effect of audio and visual source distance on perceived simultaneity when distances are presented interleaved or blocked during the course of the experiment.Participants performed temporal order judgments of audiovisual stimuli presented from speakers and LEDs located at 1 and 16 m. Sounds and lights sources could be either co-located or dislocated as the distances of the sound and light sources were combined. The four distance conditions were either presented interleaved or blocked throughout the course of the experiment.As expected, we find that sound source distance requires beeps to be presented earlier to appear simultaneous with flashes. We also find that light source distance requires flashes to be presented earlier to appear simultaneous with beeps. Interestingly, the effect of sound source distance is higher with blocked presentation whereas the effect of light source distance is larger than sound source distance (but opposite in sign) when the four distance conditions are presented randomly interleaved. This effect can be related to peripheral viewing of the light sources in the interleaved condition and it suggests that scenes with audio-visual events at several distances could be perceived simultaneously without the need for a perceptual mechanism that use distance cues to maintain perceptual synchrony.

Fast Maximum Likelihood Localization of Near-Field Sources

Conventional methods for locating near-field sources generally suffer performance degradation when the assumption of uniform spatial Gaussian noise does not hold. In this paper study the scenario of non-uniform spatial Gaussian noise. First we construct the near-field signal model based on planar sensor array and derive the maximum likelihood method for obtaining the azimuth and distance of sound sources, then we proposed two fast algorithms-stepwise-concentrated maximum likelihood method(SML) and approximate maximum likelihood method(AML) to reduce the high computational complexity of maximum likelihood localization method. Simulation results show that the two proposed methods outperform conventional maximum likelihood method, with lower computational complexity and less mean squared error of both azimuth estimation and distance estimation.

The effect of interaural-level-difference fluctuations on the externalization of sound

Real-world sound sources are usually perceived as externalized and thus properly localized in both direction and distance. This is largely due to (1) the acoustic filtering by the head, torso, and pinna, resulting in modifications of the signal spectrum and thereby a frequency-dependent shaping of interaural cues and (2) interaural cues provided by the reverberation inside an enclosed space. This study first investigated the effect of room reverberation on the spectro-temporal behavior of interaural level differences (ILDs) by analyzing dummy-head recordings of speech played at different distances in a standard listening room. Next, the effect of ILD fluctuations on the degree of externalization was investigated in a psychoacoustic experiment performed in the same listening room. Individual binaural impulse responses were used to simulate a distant sound source delivered via headphones. The ILDs were altered using a gammatone filterbank for analysis and resynthesis, where the envelopes of the left and right-ear signals were modified such that the naturally occurring fluctuations of the ILDs were restricted. This manipulation reduced the perceived degree of externalization. This was consistent with the analysis of short-term ILDs at different distances showing that a decreased distance to the sound source also reduced the ILD fluctuations.

Sound Source Distance Estimation in Rooms based on Statistical Properties of Binaural Signals

A novel method for the estimation of the distance of a sound source from binaural speech signals is proposed. The method relies on several statistical features extracted from such signals and their binaural cues. Firstly, the standard deviation of the difference of the magnitude spectra of the left and right binaural signals is used as a feature for this method. In addition, an extended set of additional statistical features that can improve distance detection is extracted from an auditory front-end which models the peripheral processing of the human auditory system. The method incorporates the above features into two classification frameworks based on Gaussian mixture models and Support Vector Machines and the relative merits of those frameworks are evaluated. The proposed method achieves distance detection when tested in various acoustical environments and performs well in unknown environments. Its performance is also compared to an existing binaural distance detection method.

Environmental reverberation affects processing of sound intensity in right temporal cortex

Although sound reverberation is considered a nuisance variable in most studies investigating auditory processing, it can serve as a cue for loudness constancy, a phenomenon describing constant loudness perception in spite of changing sound source distance. In this study, we manipulated room reverberation characteristics to test their effect on psychophysical loudness constancy and we tested with magnetoencephalography on human subjects for neural responses reflecting loudness constancy. Psychophysically, we found that loudness constancy was present in strong, but not weak, reverberation conditions. In contrast, the dependence of sound distance judgment on actual distance was similar across conditions. We observed brain activity reflecting behavioral loudness constancy, i.e. inverse scaling of the evoked magnetic fields with distance for weak reverberation but constant responses across distance for strong reverberation from ~210 to 270ms after stimulus onset. Distributed magnetoencephalography source reconstruction revealed underlying neural generators within the right middle temporal and right inferior anterior temporal lobe. Our data suggest a dissociation of loudness constancy and distance perception, implying a direct usage of reverberation cues for constructing constant loudness across distance. Furthermore, our magnetoencephalography data suggest involvement of auditory association areas in the right middle and right inferior anterior temporal cortex in this process.

Fenomena Perbedaan Tingkat Kebisingan pada 2 Unit Ruang Tidur: Studi Kasus Rumah Tinggal Peneliti di Tepi Jalan Raya

Resting is essential to restore the freshness of body both physically and mentally. To optimally gain freshness quality depends on a conducive and comfortable atmosphere during resting time. Architecture also makes convenience factor as a basis for managing comfort zones as classification placement for room specification. One convenience aspect to consider is the noise level, so it is natural that the resting room (bedroom) is placed in zones that are considered quiet, away from the noise level. Theoritically, noise is getting weaker as the sound source distance is getting further. Sound source will also propagate or bounce on a specific object. On contrary, in this case (at the researcher’s residential), the rooms closer to the sound source are even have lower noise levels due to the lower position and barrier block.

Effects of interaural level differences on the externalization of sound

Distant sound sources in our environment are perceived as externalized and are thus properly localized in both direction and distance. This is due to the acoustic filtering by the head, torso, and external ears, which provides frequency-dependent shaping of binaural cues such as interaural level differences (ILDs) and interaural time differences (ITDs). In rooms, the sound reaching the two ears is further modified by reverberant energy, which leads to increased fluctuations in short-term ILDs and ITDs. In the present study, the effect of ILD fluctuations on the externalization of sound was investigated. A psychoacoustic experiment was performed in a standard IEC 268-13 listening room by normal-hearing listeners. Individual binaural room impulse responses were used to simulate a distant speech source delivered via headphones. The speech signal was then processed such that the naturally occurring fluctuations in the ILDs were compressed, while the ITDs were preserved. This manipulation reduced the perceived degree of externalization mainly for broadband and highpass filtered speech. In the case of lowpass filtered speech, the compression of ILD fluctuations did not affect externalization. Overall, for sounds that contain frequencies above about 1 kHz the ILD fluctuations were found to be an essential cue for externalization.

The distance-dependence of interaural level difference cues to sound location and their encoding by neurons the inferior colliculus – implications for the Duplex theory

The Duplex theory posits that low- and high-frequency sounds are localized using two different acoustical cues, interaural time (ITDs) and level (ILDs) differences, respectively. Anatomically, ITDs and ILDs are separately encoded in two parallel pathways consistent with ecological and efficiency principles which state that neural systems evolved strategies to represent the full spectrum of sensory signals as experienced by an organism in its natural habitat. ILDs are location and frequency dependent such that lower and higher frequencies exhibit smaller and larger ILDs, respectively. Neurons throughout the auditory neuraxis encode ILDs for high-frequency sounds. However, although low-frequency ILDs are negligible, humans are quite sensitive to them and physiological studies report low-frequency ILD sensitive neurons. The presence of such neurons is at odds with the Duplex theory and ecological and efficiency principles. We suggest these discrepancies arise from inadequate understanding of the ecological acoustical environment. Via measurements in the chinchilla of acoustical ILDs and their encoding by inferior colliculus neurons the hypothesis is explored that low-frequency ILDs become useful when sound source distance is varied. We demonstrate that a population of neurons is sufficient to encode the frequency-dependent range of ILDs that would be experienced as a function of location and distance. (R01-DC01155)

Approaches to the study of neural coding of sound source location and sound envelope in real environments

The major functions of the auditory system are recognition (what is the sound) and localization (where is the sound). Although each of these has received considerable attention, rarely are they studied in combination. Furthermore, the stimuli used in the bulk of studies did not represent sound location in real environments and ignored the effects of reverberation. Another ignored dimension is the distance of a sound source. Finally, there is a scarcity of studies conducted in unanesthetized animals. We illustrate a set of efficient methods that overcome these shortcomings. We use the virtual auditory space method (VAS) to efficiently present sounds at different azimuths, different distances and in different environments. Additionally, this method allows for efficient switching between binaural and monaural stimulation and alteration of acoustic cues singly or in combination to elucidate neural mechanisms underlying localization and recognition. Such procedures cannot be performed with real sound field stimulation. Our research is designed to address the following questions: Are IC neurons specialized to process what and where auditory information? How does reverberation and distance of the sound source affect this processing? How do IC neurons represent sound source distance? Are neural mechanisms underlying envelope processing binaural or monaural?

Assessment of Urban Soundscapes

This article presents the different tools for assessing soundscapes within urban public spaces and develops in particular the use of the sonic mind map. We will successively define the notions of sonic perception and representation, and sonic and spatial evaluation; we will approach the concept of soundscape and finally give details about the sonic mind-map tool. Through this tool, the soundscape of urban public spaces can be understood, not through speech analysis, but through spatial representations of memorised sonic ambiances.Investigation results based among other things on sonic mind-map analyses explain the significance of sonic spatialisation and of the sound source distance in urban soundscape assessment. Using the sonic mind map to analyse the sonic representations associated with certain urban spaces seems to be relevant for researchers in space sciences or even for urban planners.