Browsing by Department "Communication Acoustics: Spatial Sound and Psychoacoustics"

Now showing 1 - 10 of 10
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    Applications of Spatially Localized Active-Intensity Vectors for Sound-Field Visualization
    (AUDIO ENGINEERING SOC, 2019-11) McCormack, Leo; Delikaris-Manias, Symeon; Politis, Archontis; Pavlidi, Despoina; Farina, Angelo; Pinardi, Daniel; Pulkki, Ville; Dept Signal Process and Acoust; University of Crete; University of Parma; Communication Acoustics: Spatial Sound and Psychoacoustics
    The purpose of this article is to detail and evaluate three alternative approaches to sound-field visualization, which all employ the use of spatially localized active-intensity (SLAI) vectors. These SLAI vectors are of particular interest, as they allow direction-of-arrival (DoA) estimates to be extracted in multiple spatially localized sectors, such that a sound source present in one sector has reduced influence on the DoA estimate made in another sector. These DoA estimates may be used to visualize the sound-field by either: (I) directly depicting the estimates as icons, with their relative size dictated by the corresponding energy of each sector; (II) generating traditional activity maps via histogram analysis of the DoA estimates; or (III) by using the DoA estimates to reassign energy and subsequently sharpen traditional beamformer-based activity maps. Since the SLAI-based DoA estimates are continuous, these approaches are inherently computationally efficient, as they forego the need for dense scanning grids to attain high-resolution imaging. Simulation results also show that these SLAI-based alternatives outperform traditional active-intensity and beamformer-based approaches, for the majority of cases.
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    Beamforming with a volumetric array of massless laser spark sources—Application in reflection tracking
    (2015) Eskelinen, Joona; Delikaris-Manias, Symeon; Gómez Bolaños, Javier; Hæggström, Edward; Pulkki, Ville; Communication Acoustics: Spatial Sound and Psychoacoustics
    A volumetric array of laser-induced air breakdown sparks is used to produce a directional and steerable acoustic source. The laser breakdown array element is broadband, point-like, and massless. It produces an impulse-like waveform in midair, thus generating accurate spatio-temporal information for acoustic beamforming. A laser-spark scanning setup and the concept of a massless steerable source are presented and evaluated with a cubic array by using an off-line far field delay-and-sum beamforming method. This virtual acoustic array with minimal source influence can, for instance, produce narrow transmission beams to obtain localized and directional impulse response information by reflection tracking.
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    Benefits and applications of laser-induced sparks in real scale model measurements
    (2015) Gómez Bolaños, Javier; Delikaris-Manias, Symeon; Pulkki, Ville; Eskelinen, Joona; Hæggström, Edward; Jeong, Cheol-Ho; Communication Acoustics: Spatial Sound and Psychoacoustics
    The characteristics of using a laser-induced spark as a monopole source in scale model measurements were assessed by comparison with an electric spark and a miniature spherical loudspeaker. Room impulse responses of first order directivity sources were synthesized off-line using six spatially distributed sparks. The source steering direction was scanned across the horizontal and vertical plane to assess the origin of early reflections. The results confirm that the characteristics of the laser-induced spark outperform those of typical sources. Its monopole characteristics enable the authors to synthesize room responses of directional sources, e.g., to obtain directional information about reflections inside scale models.
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    Controlling the perceived distance of an auditory object by manipulation of loudspeaker directivity
    (2015) Laitinen, Mikko-Ville; Politis, Archontis; Huhtakallio, Ilkka; Pulkki, Ville; Communication Acoustics: Spatial Sound and Psychoacoustics
    This work presents a method to control the perceived distance of an auditory object by changing the directivity pattern of a loudspeaker and consequently the direct-to-reverberant ratio at the listening spot. Control of the directivity pattern is achieved by beamforming using a compact multi-driver loudspeaker unit. A small-sized cubic array consisting of six drivers is assembled, and per driver beamforming filters are derived from directional measurements of the array. The proposed method is evaluated using formal listening tests. The results show that the perceived distance can be controlled effectively by directivity pattern modification.
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    A database of near-field head-related transfer functions based on measurements with a laser spark source
    (Elsevier Ltd, 2023-02-28) Marschall, Marton; Gomez Bolanos, Javier; Prepelita, Sebastian; Pulkki, Ville; Communication Acoustics: Spatial Sound and Psychoacoustics; Department of Information and Communications Engineering
    This paper presents a database of near-field head-related transfer functions (HRTFs) of an artificial head, measured at four distances (0.2, 0.3, 0.4 and 0.5 m), with 49 positions recorded at each distance, for a total of 196 measurement points. The HRTFs were recorded using an acoustic pulse created by a laser-induced breakdown of air (LIB), which realizes a close to ideal, massless, monopole sound source. While the LIB produces a high amplitude pressure pulse, the amplitude decays toward low frequencies, which introduced a low frequency limit of about 200 Hz for this particular setup. Thus, a spherical head model based on the analytical expression for scattering by a rigid sphere was fitted to the measured data, and used to extend the low frequency range of the measurements. A brief evaluation of the processed dataset was undertaken, considering interaural time and level differences. The measured and processed database, as well as the low frequency extension procedure are made publicly available to support future research into nearby sound localization, and virtual/augmented reality applications.
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    Laser-induced acoustic point source for accurate impulse response measurements within the audible bandwidth
    (2014) Gómez Bolaños, Javier; Delikaris-Manias, Symeon; Pulkki, Ville; Eskelinen, Joona; Hæggström, Edward; Communication Acoustics: Spatial Sound and Psychoacoustics
    Laser induced air breakdown is proposed as a sound source for accurate impulse response measurements. Within the audible bandwidth, the source is repeatable, broadband, and omnidirectional. The applicability of the source was evaluated by measuring the impulse response of a room. The proposed source provides a more accurate temporal and spatial representation of room reflections than conventional loudspeakers due to its omnidirectionality, negligible size and short pulse duration.
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    Neural realignment of spatially separated sound components
    (2015) Salminen, Nelli H.; Takanen, Marko; Santala, Olli; Alku, Paavo; Pulkki, Ville; Speech Communication Technology; Communication Acoustics: Spatial Sound and Psychoacoustics; Department of Neuroscience and Biomedical Engineering
    Natural auditory scenes often consist of several sound sources overlapping in time, but separated in space. Yet, location is not fully exploited in auditory grouping: spatially separated sounds can get perceptually fused into a single auditory object and this leads to difficulties in the identification and localization of concurrent sounds. Here, the brain mechanisms responsible for grouping across spatial locations were explored in magnetoencephalography (MEG) recordings. The results show that the cortical representation of a vowel spatially separated into two locations reflects the perceived location of the speech sound rather than the physical locations of the individual components. In other words, the auditory scene is neurally rearranged to bring components into spatial alignment when they were deemed to belong to the same object. This renders the original spatial information unavailable at the level of the auditory cortex and may contribute to difficulties in concurrent sound segregation.
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    Sound Source Localization Using Sector-Based Analysis With Multiple Receivers
    (2021) McCrea, Michael; McCormack, Leo; Pulkki, Ville; Communication Acoustics: Spatial Sound and Psychoacoustics; Dept Signal Process and Acoust
    The success of parametric approaches to spatial sound reproduction and sound field navigation depend on the accuracy of the initial analysis and decomposition of the sound field. In this work, the sector-based high-order extension to intensimetric sound field analysis is evaluated in the context of 3D source localization. The evaluation is performed with simulations of ideal spherical harmonic receiver signals using two intensimetric estimators: source direction of arrival and sound field diffuseness. The technique is first assessed for a single receiver with regard to influential factors of analysis order, source incidence angle, and the presence of diffuse noise. The technique is then applied to 3D source localization, utilizing concurrent analyses from multiple receivers. Results for different analysis orders are compared and mitigating factors for robust localization over a broad spatial region are discussed. Optimization strategies targeting specific conditions are proposed, tested, and found to improve localization accuracy.
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    Transmission line cochlear models: Improved accuracy and efficiency
    (2014) Altoè, Alessandro; Verhulst, Sarah; Pulkki, Ville; Communication Acoustics: Spatial Sound and Psychoacoustics
    This paper presents an efficient method to compute the numerical solutions of transmission-line (TL) cochlear models, and its application on the model of Verhulst et al. The stability region of the model is extended by adopting a variable step numerical method to solve the system of ordinary differential equations that describes it, and by adopting an adaptive scheme to take in account variations in the system status within each numerical step. The presented method leads to improve simulations numerical accuracy and large computational savings, leading to employ TL models for more extensive simulations than currently possible.
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    When Spatial Sounds Affect the Ability to Apprehend Visual Information: A Physiological Approach
    (Audio Engineering Society, 2023-10) Mendonça, Catarina; Wang, Heng; Pulkki, Ville; University of Porto; Dept Signal Process and Acoust; Communication Acoustics: Spatial Sound and Psychoacoustics; Department of Information and Communications Engineering
    The current technological solutions for spatial audio provide realistic auditory impressions but rarely account for multisensory interactions. The intent of this study was to discover if and when spatial sounds could lower the accuracy of visual perception. Sequences of light and sound events were presented, and different sound parameters were tested: spatial and temporal congruency, horizontal and vertical spatial distribution, and source broadness. Participants were asked to report the location of the last visual event, in a left-right discrimination task. During the task, cognitive effort was monitored through pupil size measurements. It was found that both spatial and temporal congruence are important for higher accuracy levels and lower cognitive effort levels. However, spatial congruence was found to not be crucial, if sounds occur within the same spatial region as visual events. Sounds hindered the visual accuracy levels and increased effort when they occurred within a narrower or wider field than thatof the visual events, but not too discrepant. These effects were replicated with vertical sound distributions.Broad sounds made the task more effortful and limited negative effects of spatially mismatched audiovisual events. When creating spatial sound for audiovisual reproductions, source distribution and broadness should be intentionally controlled.