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- Ahrens, Jens, 1978
(författare)
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A Software Tool For Auralization of Simulated Sound Fields
- 2023
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Ingår i: Proceedings of the Institute of Acoustics. - 1478-6095. ; 45
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Konferensbidrag (refereegranskat)abstract
- We demonstrated an implementation of a set of methods for auralization of simulated sound fields. For the chosen grids of head size and of 343 pressure points or 100 or 150 sampling points for both pressure and pressure gradient, respectively, the binaural output signals of the methods deviate from the ground truth only at high frequencies and mostly on the contralateral side, which makes the output perceptually very similar to the ground truth. What combination of grid type, grid dimensions, and number of sampling points produces perceptually transparent auralization (i.e. an auralized signal that is perceptually indistinguishable from the ground truth) is unclear at this stage and is subject to further research. It is conceivable that such a combination can be found. The presented methods will then constitute a unified approach to auralization as they can be applied to any acoustical simulation method, be it wave-based, geometric, or energy-based, so long as the simulation method allows for computing volumetric sound pressure data. Simulation methods can thereby be compared perceptually without uncertainty regarding the influence of the auralization method on the result. © 2023 Institute of Acoustics. All rights reserved.
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| 2. |
- Ahrens, Jens, 1978, et al.
(författare)
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Authentic Auralization of Acoustic Spaces Based on Spherical Microphone Array Recordings
- 2018
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Ingår i: Proceedings of the Institute of Acoustics. - 1478-6095. ; 40:3, s. 303-310
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Konferensbidrag (refereegranskat)abstract
- Many approaches for the capture and auralization of real acoustic spaces have been proposed over the past century. Limited spatial resolution on the capture side has typically been the factor that caused compromises in the achievable authenticity of the auralization. Recent advancements in the field of spherical microphone arrays provide new perspectives for both headphone-based and loudspeaker-based auralization. It has been shown that a bowling-ball-size spherical array of around 90 microphones allows for creating signals at the ears of the listener that are perceptually almost indistinguishable from the ear signals that arise in the original space. Head-tracked headphone auralization, i.e. playback that adapts to the instantaneous head orientation of the listener, has been shown to provide the best results. In the present contribution, we provide an overview of the technology and demonstrate the latest research advancements and remaining challenges.
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| 5. |
- Kang, Jian, et al.
(författare)
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Effect of vegetation on noise propagation in streets and squares
- 2012
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Ingår i: Proceedings of the Institute of Acoustics. - 1478-6095. - 9781618398512 ; 34:PART 1, s. 57-67
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Konferensbidrag (refereegranskat)abstract
- This paper focuses on noise mitigation using vegetation in urban streets and squares of geometries typical for European city centres. Simulations of noise propagations have been performed using energybased CRR (combined ray-tracing and radiosity) and wave-based PSTD (pseudospectral time-domain) methods. The noise abetment schemes included the placement of vegetation on building facades and on low-profile barriers. Generally good agreement between the simulation methods has been achieved for the cases with vegetation on the facades, although for the cases with barriers the effect of diffraction at low frequencies shows the limitation of the CRR method. Considering a relatively high broadband absorption of 0.33 for facades as the reference cases, when vegetation is applied on all facades, a SPL decrease of up to 0.7dB and of up to 1dB can be achieved in the street and square, respectively. The insertion of a low-profile barrier in the street and the square can result in a decrease in SPL of up to 3dB and up to 4.5dB, respectively. Decreasing the absorption coefficient from 0.33 to 0.1 as the reference cases would result in an increase of broadband insertion loss by 2dB in the street and by 2.5dB in the square with vegetated facades.
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| 6. |
- Starkhammar, Josefin, et al.
(författare)
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Acoustic Touch Screen for Dolphins, First application of ELVIS - an Echo-Location Visualization and Interface System
- 2007
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Ingår i: 4th International Conference on Bio-Acoustics 2007. - 1478-6095. - 9781604238082 ; 29:part 3, s. 63-68
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Konferensbidrag (refereegranskat)abstract
- Dolphin sonar has been extensively studied over several decades, and much of its basic characteristics are well known (Au 1993). However, most of these studies have been based on an experimental setup where the dolphin has been trained to be voluntarily fixed, so its directional sonar beam could be recorded with fixed hydrophones. Although this allows for very exact measurements, it most likely has prevented the full dynamic potential of the dolphin’s sonar to be revealed. Also the dolphin’s response to scientific questions, e.g. in target detection threshold or discrimination trials, mostly has been a “go/no go” response or pressing a yes/no paddle. This traditional experimental methodology to measure the response makes rather coarse indications of choice. It is difficult to refine and will be unpractical with a multi-choice paradigm. Therefore a new EchoLocation Visualisation and Interface System (ELVIS) has been developed at Lund University in cooperation with Kolmården Wild Animal Park, and is presently being used in dolphin food preference investigations at the Kolmården Dolphinarium. ELVIS basically consists of a matrix of 16 hydrophones attached to a semi transparent screen lowered into the water of the pool where the dolphins swim freely. The hydrophones hit by a sonar pulse generate electric signals in relation to the received sound pressure level. After subsequent amplification these signals are transferred to a computer. The signal analysis is performed by custom designed LabVIEW software that constitutes the core of the interactive features of the interface system. The software can for example in real time create a round colour spot on the computer screen, corresponding to the maximum intensity in the sound beam. The recorded sound intensity can be coded into colour and/or light intensity. The resulting image on the computer screen is continuously projected back onto the hydrophone matrix screen, hence giving the dolphin an immediate visual feedback to its sonar output. Since only 16 hydrophones were used, the exact location of the maximum sound intensity point was derived through interpolation between the hydrophones in the matrix. This made the spatial resolution of the sound beam recordings quite sufficient for the present study. However, future systems will certainly rely on increased hydrophone matrix size. This system offers a whole new experimental methodology in dolphin research since it can function as an acoustic “touch screen” for the dolphins. It is highly adaptable to different studies since the core of the interface features is software based.In cognitive studies with primates, e.g. the chimpanzee, a computerized symbol interface, based on a finger operated touch screen, has been successfully used (Rumbaugh et al. 1975). Even with birds, like chickens and doves, this approach has been used (Cheng & Spetch, 1995). So far, however, it has not been attempted with dolphins, partly due to the inherent problems in using electronics in salt water. However, the ELVIS screen is based on acoustic detection and activation, using hydrophones, which is well suited for underwater use. The software used in the present experiment designate active areas on the screen, indicated by white symbols, e.g. a filled circle or a filled square. When the dolphin aims its sonar beam axis at this symbol, it flashes to indicate a “hit” and a bridging stimulus (a 400 ms, 10 kHz sinus tone) is played. In this study each of four such symbols represented a different fish (herring, mackerel, capelin and squid). When the dolphin “clicked” on one of them, it was rewarded by the fish represented by it. Thereby the dolphin could choose what kind of fish it preferred. Hence, for the first time the dolphins could execute and run a computer program using their sonar beam like we use a mouse cursor. The size and trig level of these “buttons” or active areas of the screen can easily be altered so that, as the dolphin’s skills in handling the program increased, the more accurate hits and more distinct sound pressure levels of the dolphin’s sound beam could be required.Three bottlenose dolphins (Tursiops truncatus) were trained to perform the task of pointing their sonar beam selectively on the symbols shown on the ELVIS screen. They quickly learned this task and were highly motivated to explore it.
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