Acoustic Objects Research Articles

Influence of visual cues on localization of acoustic sound sources in old adults

Localization accuracy of stationary acoustic objects is reduced as people grow older. While it is known that this reduction can be caused by many age-related declines in the peripheral sensory system, at central cortical levels as well as in cognitive processes, it is not known how much localization performance is influenced by concurrent congruent and/or incongruent spatial information from a different sensory system, e.g., vision. In the present study we examined localization accuracy of young and old adults to acoustic stimuli that were presented simultaneously to a visual stimulus that was either spatially congruent or spatially disparate (by ±5°/±10°/±15°) in acoustic free field. The acoustic reference position was presented at frontal (9°), para-frontal (30°), and lateral (64°) positions. To infer how strongly the visual cue interacted with the auditory stimulus a unification task was examined. Here, acoustic and visual stimulus combinations were the same as in the localization task. Participants were instructed to indicate whenever both visual and acoustic information matched in terms of their spatial position. Localization accuracy was not influenced by the visual cue in young adults, but the influence of the visual distractor was strong in old adults, i.e., visual bias was strong. These observations were supported by the unification task where old adults had increased perception of congruent audio–visual directions at all reference positions and even at very large disparities (e.g., ±15°). Conclusively, concurrent information from different sensory systems highly influences auditory localization accuracy in older adults, supporting the notion that multisensory integration is enhanced in older adults.

Superspheroidal modeling of resonance scattering from elongated air bubbles and fish swim bladders

The extended boundary condition technique of Waterman [J. Acoust. Soc. Am. 45, 1417-1429 (1969)] has been used to make accurate studies of the frequency and azimuthal scattering distributions from extended axisymmetric acoustic objects. These objects are formed using the mathematical function for a "superellipse" [i.e., (x/a)(s) + z/b)(s) = 1, where s = 2n, n = 1,2,[ellipsis (horizontal)]], and revolving around the z-axis. For s = 2, the object is a spheroid with aspect ratio α = b/a. As s increases, the shape of the object approaches a right circular cylinder of diameter 2a and length 2b. The method is applied to the case of prolate (i.e., α > 1) air-filled objects in water, which has importance for the interpretation of acoustic scattering from oceanic objects such as air-bubbles, the swim bladders of some fish, and zooplankton. It is found that the resonance frequency increases with α, essentially as predicted using a different method by Weston, and increases in a relatively minor way with s. The resonance peak amplitude, and Q, are also more sensitive to changes in α, than s. The method shows that the monopole resonance continues to dominate low frequency scattering, leading to an almost spherically symmetric azimuthal scattering distribution, even for elongated, cylindrical, air-filled, objects with an aspect ratio up to α = 20, and s = 32.

Scattering from highly extended acoustical objects using multiple precision computation

The extended boundary condition (or “T-matrix”) technique of Waterman [J. Acoust. Soc. Am., 45, 1417-1429 (1969)] has recently been used to study scattering from highly non-spherical axisymmetric air-filled acoustical objects in water. Evaluation of the T-matrix for extended objects is frequently problematical, typically requiring the inversion of very large and highly ill-conditioned matrices. A second issue is computation of the matrix elements themselves, requiring accurate numerical quadrature of the surface integrals around the scattering object. In this work, a computational scheme was implemented using MATLAB®, and a freely downloadable software package “mptoolbox,” which enables numerical computations to be performed to arbitrary degrees of precision. Here, it was implemented with 250 bits of precision specified for the mantissa part of the number, leading to computations with about 75 decimal places of accuracy. Using a multiple precision method significantly improved the stability and accuracy of both types of operations and indicates a powerful tool for the successful implementation of many scattering and other acoustical problems demanding high precision computational schemes. [Work supported by ONR.]

Vibro-acoustic optimization of an immersed cylindrical structure with a floating-raft system inside by using frequency-response-function-based substructuring sensitivity analysis

Optimization of the vibration transmission of an internal floating-raft system and the resultant sound radiation of the fluid-loaded cylindrical structure is presented. The influences of different objective functions, fluid loading, external loading, and an optimized frequency band on the optimization results are investigated in detail. The frequency-response-function (FRF)-based substructuring method and the coupled finite element method–boundary element method are employed to study the vibration transmission from vibrating machines to the base and the vibro-acoustic behaviour of the fluid-loaded cylindrical structure respectively. An FRF-based substructuring sensitivity analysis is applied to obtain the optimal values of the stiffness of isolators under five objective functions in the low-frequency range. The optimized results demonstrate that some of the objective functions are equivalent to each other and can be replaced by each other. The reasons for the difference in the variation trends of the stiffness of the lower isolators for different objective functions are discussed in detail. The fluid loading does have an impact on the optimal results and it influences the variation trend of only the stiffness of the isolators that support the machines without an externally applied load. The external loading and the optimized frequency band are two factors to be carefully considered in the design stage. This investigation reveals that it should take into account fluid–structure interaction and comprehensively consider different vibration or acoustic objectives in the design stage.

Acoustical behavior of colonial churches in Cusco, Peru.

The paper searches for characterizing the acoustical behavior of more than ten colonial churches in Cusco, a southern city of Peru. Cusco was an important city through the Spaniard Colonial Era in Peru; several religious orders established in the area and fix the European styles and building process to the geography, geology and building materials. Through five typical acoustical objective parameters the acoustical environment in each church is defined. A comparison between several positions in each church analyzed and among churches will be presented.

Acoustic evaluation of a contemporary church based on in situ measurements of reverberation time, definition, and computer-predicted speech transmission index

An acoustic survey was conducted in a church with a modern architectural style in Curitiba, southern Brazil. The investigation used acoustic measurement methods to assess the acoustic quality of the nave and the results were compared with the NBR 12179 Brazilian National Standard, ISO 3382-1 international standard and IEC 60268-16 Standard. Integrated impulse responses were measured to determine two acoustic objective parameters: (1) Reverberation Time (RT), (2) Definition ( D 50) according to the international ISO/3382 and ISO/3382-1 standards. The Speech Transmission Index (STI) inside the church was calculated by computer simulation. The measured and calculated values were consistent with those proposed by the standards for speech auditoria (RT 500Hz = 1.18 s, D 50 > 50% and STI > 0.45), and are in line with the music and speech intelligibility requirements resulting from the Second Ecumenical Council of the Vatican in 1965, whose liturgical reforms involved the adoption of vernacular languages in place of Latin for religious service.

Acoustic Sensor-Based Multiple Object Tracking with Visual Information Association

Object tracking by an acoustic sensor based on particle filtering is extended for the tracking of multiple objects. In order to overcome the inherent limitation of the acoustic sensor for the simultaneous multiple object tracking, support from the visual sensor is considered. Cooperation from the visual sensor, however, is better to be minimized, as the visual sensor's operation requires much higher computational resources than the acoustic sensor-based estimation, especially when the visual sensor is not dedicated to object tracking and deployed for other applications. The acoustic sensormainly tracks multiple objects, and the visual sensor supports the tracking task only when the acoustic sensor has a difficulty. Several techniques based on particle filtering are used for multiple object tracking by the acoustic sensor, and the limitations of the acoustic sensor are discussed to identify the need for the visual sensor cooperation. Performance of the triggering-based cooperation by the two visual sensors is evaluated and compared with a periodic cooperation in a real environment.

Intensity invariance properties of auditory neurons compared to the statistics of relevant natural signals in grasshoppers

The temporal pattern of amplitude modulations (AM) is often used to recognize acoustic objects. To identify objects reliably, intensity invariant representations have to be formed. We approached this problem within the auditory pathway of grasshoppers. We presented AM patterns modulated at different time scales and intensities. Metric space analysis of neuronal responses allowed us to determine how well, how invariantly, and at which time scales AM frequency is encoded. We find that in some neurons spike-count cues contribute substantially (20-60%) to the decoding of AM frequency at a single intensity. However, such cues are not robust when intensity varies. The general intensity invariance of the system is poor. However, there exists a range of AM frequencies around 83 Hz where intensity invariance of local interneurons is relatively high. In this range, natural communication signals exhibit much variation between species, suggesting an important behavioral role for this frequency band. We hypothesize, just as has been proposed for human speech, that the communication signals might have evolved to match the processing properties of the receivers. This contrasts with optimal coding theory, which postulates that neuronal systems are adapted to the statistics of the relevant signals.

In Between as a Permanent Status: Milan Adamčiak's Version of Intermedia

ABSTRACT Milan Adamčiak is a Slovak composer, cellist and musicologist; creator of acoustic objects, installations and unconventional musical instruments; a performer, visual artist and experimental poet. Traditionally trained but influenced by Cagean and Fluxus poetics, he created from the late 1960s until the mid-1990s a large body of work that transgressed the conventional definitions of art creativity and quickly moved toward the concepts of opera aperta, action music and various intermedia forms. At the same time he was experimenting with electronic media, he created several pieces of electroacoustic music and musique concrÈte, but it was primarily live electronics that fit the principles of his radical poetics. The author considers Adamčiak's intermedia in the context of philosophical and aesthetical thought, revealing mutual correspondences, apparent as well as hidden.

Scattering from superspheroidal acoustic objects.

The extended boundary condition technique of Waterman [J. Acoust. Soc. Am. 45, 1417–1429 (1969)] has been used to study scattering from extended axisymmetric acoustic objects. These objects are formed using the mathematical function for a “super-ellipse” [i.e., (x/a)s + (z/b)s=1, where s=2n, n=1, 2, 3,…] and revolving around the z-axis. For s=2, the object is a spheroid with aspect ratio α=b/a. As s increases, the shape of the object approaches a right circular cylinder of radius a and length 2b. The method allows the scattered field to be accurately determined for all azimuthal angles as a function of frequency. The method is applied to the case of air-filled objects in water, which has importance for the interpretation of acoustic scattering from oceanic objects such as air-bubbles, the swim bladders of some fish, and zooplankton. It is found that the frequency increases with α, exactly as predicted using a geometrical method by Weston, and increases in a relatively minor way with $s$. In addition, the method shows that the monopole resonance, which leads to a spherically symmetric scattering distribution, continues to dominate low-frequency scattering even for cylindrically shaped, air-filled objects with an aspect ratio up to α=40 and s=32.

“Beautiful Murmurs”: Stethoscopic Listening and Acoustic Objectification

ABSTRACTAcademic thought on the senses has tended to position objectification as intrinsic to vision and acts of looking (Grosz 1992). Audition and listening, on the other hand, have been imagined as creating an intimate and participatory form of sensory engagement which does not produce objectification (Stoller 1989; Gell 1995). Drawing on fieldwork conducted among medical students, this article details how the teaching of auscultation or stethoscopic listening centers on patients whose conditions create heart sounds known as “murmurs,” which are important diagnostic signs. These patients, and the sounds their hearts produce, become the focus of numerous stethoscopic examinations. Patients are conscious of the way in which clinical auscultation reifies their heart sounds, constructing murmurs as discrete acoustic objects inside their bodies. They also resent feeling objectified as clinical curiosities through repeated listening. The notion that objectification may be brought about through an acoustic practice invites a reappraisal of the perceptual possibilities of audition. Following Bubandt (1998) and Ingold (2000), the article argues that studies of perception should be grounded in the dynamics of particular sensory practices, rather than in preconceived, generalized notions of sight and hearing.

Toward automatic music transcription from audio input.

Transcribing audio input to obtain a music score has been a basic but yet hard problem in music signal and information processing. It can be paralleled with continuous speech recognition comprising of acoustic analysis, acoustic model, language model, and decoder. This presentation discusses functional modules for the music case, i.e., estimation of multiple fundamental frequencies, rhythm models, and chord modeling. For multi‐F0 estimation, a computational auditory scene analysis‐motivated approach is taken to model human hearing where each acoustic object is modeled with Gaussian mixture both along frequency and time axis [Kameoka (2005)]. An extended EM‐algorithm is applied to iterative estimation of fundamental frequencies and onset/offset timings of music notes contained in the given spectrogram of the audio input. As for rhythm estimation, HMM is used to model the sequence of note lengths where tempo is treated in the model as a varying hidden variable [Takeda (2006)]. Chord progression is also modeled with HMM [Kawakami (2000)] where transition probabilities between chords and emission probabilities of notes from the hypothesized chord have been trained with a music database. Related issues are also discussed including other approaches to multiple fundamental frequencies with specmurt analysis [Sagayama (2005)], non‐negative matrix factorization [Raczynski (2007)], and timber modeling [Miyamoto (2007)].

Predicting acoustic orientation in complex real-world environments

Animals have to accomplish several tasks in their lifetime, such as finding food and mates and avoiding predators. Animals that locate these using sound need to detect, recognize and localize appropriate acoustic objects in their environment, typically in noisy, non-ideal conditions. Quantitative models attempting to explain or predict animal behaviour should be able to accurately simulate behaviour in such complex, real-world conditions. Female crickets locate potential mates in choruses of simultaneously calling males. In the present study, we have tested field cricket acoustic orientation behaviour in complex acoustic conditions in the field and also successfully predicted female orientation and paths under these conditions using a simulation model based on auditory physiology. Such simulation models can provide powerful tools to predict and dissect patterns of behaviour in complex, natural environments.

Evidence for spatial representation of object shape by echolocating bats (Eptesicus fuscus)

Big brown bats were trained in a two-choice task to locate a two-cylinder dipole object with a constant 5 cm spacing in the presence of either a one-cylinder monopole or another two-cylinder dipole with a shorter spacing. For the dipole versus monopole task, the objects were either stationary or in motion during each trial. The dipole and monopole objects varied from trial to trial in the left-right position while also roving in range (10-40 cm), cross range separation (15-40 cm), and dipole aspect angle (0 degrees -90 degrees ). These manipulations prevented any single feature of the acoustic stimuli from being a stable indicator of which object was the correct choice. After accounting for effects of masking between echoes from pairs of cylinders at similar distances, the bats discriminated the 5 cm dipole from both the monopole and dipole alternatives with performance independent of aspect angle, implying a distal, spatial object representation rather than a proximal, acoustic object representation.

Hierarchical approach to voice activity detection in realistic environmental noise

The automatic identification of acoustic objects, particularly speech, in adverse backgrounds can pose a difficult problem. In this work, the problem of speech detection in different backgrounds is tackled using a hierarchical decision tree: The root node provides a coarse classification of the noise background, while the next nodes are optimised to detect speech in one particular background each. The results of this approach are compared to the ITU G729B standard VAD and to a binary classifier trained on speech vs a mixture of the backgrounds. The features employed are amplitude modulation spectra of the signals (Kollmeier & Koch, 1993) that represent the modulation content of a signal as a two-dimensional (modulation-frequency vs centre frequency) spectral pattern. The best features for classification at each node are selected independently (node-specific) using a sequential floating forward search algorithm. The statistical learner is an open source support vector machine (Chang & Lin, 2001).

Objective and subjective analysis of acoustical response in newly renovated Palais Moncalm, Quebec City, Canada

To celebrate the 75th anniversary of Palais Montcalm, the building has been almost entirely rebuilt to convert it into the House of Music. The main room, named Salle Raoul-Jobin, has been designed specifically for the resident chamber orchestra: Les Violons du Roy. Collaboration between acoustical consultant, Larry S. King, and architect Jacques Plante of MUSE consortium results in a 979 seats concert hall with variable acoustic to accommodate different kinds of musical events. Since reopening in March 2007, the general acoustic has been enthusiastically acclaimed by professionals, by world known musicians, and by the public. The principal objective of this study is to characterize acoustical response of the room with various adjustments of wall curtains and motorized canopy. This important reflective area is software-controlled in a range of 3 meters depending on musical needs. Acoustical objective parameters, such as reverberation time, early decay time, impulse response or C80 factor will be analyzed and compared to musical subjective perception of a few instruments played at multiple positions on stage and for different listening locations.

Relationship between listening difficulty and acoustical objective measures in reverberant sound fields

The previous work [Morimoto et al., J. Acoust. Soc. Am. 116, 1607-1613] showed that listening difficulty ratings can be used to evaluate speech transmission performance more exactly and sensitively than intelligibility. Meanwhile, speech transmission performance is usually evaluated using acoustical objective measures, which are directly associated with physical parameters of room acoustic design. However, the relationship between listening difficulty ratings and acoustical objective measures was not minutely investigated. In the present study, a total of 96 impulse responses were used to investigate the relationship between listening difficulty ratings and several objective measures in unidirectional sound fields. The result of the listening test showed that (1) the correlation between listening difficulty ratings and speech transmission index (STI) is the strongest of all tested objective measures, and (2) A-weighted D(50), C(50), and center time, which are obtained from the impulse responses passed through an A-weighted filter, also strongly correlate with listening difficulty ratings, and their correlations with listening difficulty ratings are not statistically different from the correlation between listening difficulty ratings and STI.

Illusory spectrotemporal ripples created with binaurally correlated noise

Binaural disparities are the primary acoustic cues employed in sound localization tasks. However, the degree of binaural correlation in a sound serves as a complementary cue for detecting competing sound sources [J. F. Culling, H. S. Colburn, and M. Spurchise, "Interaural correlation sensitivity," J. Acoust. Soc. Am. 110(2), 1020-1029 (2001) and L. R. Bernstein and C. Trahiotis, "On the use of the normalized correlation as an index of interaural envelope correlation," J. Acoust. Soc. Am. 100, 1754-1763 (1996)]. Here a random chord stereogram (RCS) sound is developed that produces a salient pop-out illusion of a slowly varying ripple sound [T. Chi et al., "Spectro-temporal modulation transfer functions and speech intelligibility," J. Acoust. Soc. Am. 106(5), 2719-2732 (1999)], even though the left and right ear sounds alone consist of noise-like random modulations. The quality and resolution of this percept is systematically controlled by adjusting the spectrotemporal correlation pattern between the left and right sounds. The prominence and limited time-frequency resolution for resolving the RCS suggests that envelope correlations are a dominant binaural cue for grouping acoustic objects.

Neural network-based underwater image classification for Autonomous Underwater Vehicles

Image processing has been one of hot issues for real world robot applications such as navigation and visual servoing. In case of underwater robot application, however, conventional optical camera-based images have many limitations for real application due to visibility in turbid water, image saturation under underwater light in the deep water, and short visible range in the water. Thus, most of underwater image applications use high frequency sonar to get precise acoustic image. There have been some approaches to apply optical image processing methods to acoustic image, but performance is still not good enough for automatic classification/recognition. In this paper, a neural network-based image processing algorithm is proposed for acoustic image classification. Especially, shadow of an acoustic object is mainly used as a cue of the classification. The neural network classifies a pre-taught image from noisy and/or occlude object images. In order to get fast learning and retrieving, a Bidirectional Associative Memory (BAM) is used. It is remarked that the BAM doesn't need many learning trials, but just simple multiplication of two vectors for generating a correlation matrix. However, because of the simple calculation, it is not guaranteed to learn and recall all data set. Thus, it is needed to modify the BAM for improving its performance. In this paper, complement data set and weighted learning factor are used to improve the BAM performance. The test results show that the proposed method successfully classified 4 pre-taught object images from various underwater object images with up to 50% of B/W noise.

Voiced speech as response of a self-consistent fundamental drive

Voiced segments of speech are assumed to be composed of non-stationary acoustic objects which can be described as stationary response of a non-stationary fundamental drive (FD) process and which are furthermore suited to reconstruct the hidden FD by using a voice adapted (self-consistent) part-tone decomposition of the speech signal. The universality and robustness of human pitch perception encourage the reconstruction of a band-limited FD in the frequency range of the pitch. The self-consistent decomposition of voiced continuants generates several part-tones which can piecewise be confirmed to be topologically equivalent to corresponding acoustic modes of the excitation on the transmitter side. As topologically equivalent image of a glottal master oscillator, the self-consistent FD is suited to serve as low frequency part of the basic time-scale separation of auditive perception and to describe the broadband voiced excitation as entrained (synchronized) and/or modulated primary response. Being guided by the acoustic correlates of pitch and loudness perception, the time-scale separation avoids the conventional assumption of stationary excitation and represents the basic decoding step of an advanced precision transmission protocol of self-consistent (voiced) acoustic objects. The present study is focussed on the adaptation of the trajectories (contours) of the centre filter frequency of the part-tones to the chirp of the glottal master oscillator.