Finite-difference time-domain simulation of low-frequency room acoustic problems

Botteldooren, Dick

doi:10.1121/1.413817

Cited by 276 publications

(219 citation statements)

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“…The combination of these two methods is beneficial, and allows increasing the reality value of the numerical simulations presented here. Both methods solve the same physical sound propagation equations (in a homogeneous, non-moving atmosphere) [40][57] [55] [56]. The main difference lies in the numerical discretisation.…”

Section: Computational Approachesmentioning

confidence: 99%

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The potential of building envelope greening to achieve quietness

Renterghem

Hornikx

Forssén

et al. 2013

Building and Environment

149

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Reduction of noise is one of the multiple benefits of building envelope greening measures. The potential of wall vegetation systems, green roofs, vegetated low screens at roof edges, and also combinations of such treatments, have been studied by means of combining 2D and 3D full-wave numerical methodologies. This study is concerned with road traffic noise propagation towards the traffic-free sides of inner-city buildings (courtyards). Preserving quietness at such locations has been shown before to be beneficial for the health and well-being of citizens. The results in this study show that green roofs have the highest potential to enhance quietness in courtyards. Favourable combinations of roof shape and green roofs have been identified. Vegetated façades are most efficient when applied to narrow city canyons with otherwise acoustically hard façade materials. Greening of the upper storey's in the street and (full) façades in the courtyard itself is most efficient to achieve noise reduction. Low-height roof screens were shown to be effective when multiple screens are placed, but only on conditions that their faces are absorbing. The combination of different greening measures results in a lower combined effect than when the separate effects would have been linearly added. The combination of green roofs or wall vegetation with roof screens seems most interesting.Keywords urban sound propagation, green roofs, green walls, noise reduction, numerical simulations, road traffic noise 3 1.IntroductionThe use of vegetation has become an essential aspect in urban planning nowadays. In densely built-up city centers, building envelope greening is often the only possibility to meet this demand. These measures have many ecological advantages too, ranging from increasing the thermal insulation of the building envelope and reduction of urban heat island effects [1]- [9], acting as a buffer for storm water [9]- [14], improving air quality and increased carbon dioxide uptake [15]- [17], increasing urban biodiversity [18]- [22], providing a visually pleasant environment [23], to even crop harvesting. In addition, also from an economical point of view, building greening seem interesting [24]- [27]. Recently, the noise reducing possibilities of such building envelope greening measures have been identified [28][29] [30][31] [32].The presence of mainly acoustically rigid materials in cities (streets, bricks, concrete, glazings, etc.) leads to a strong amplification of the emitted sound from road traffic noise, and large sound pressure levels are observed in city canyons. The noise problem has indeed become one of the major environmental challenges in the urban environment. The WHO report "burden of disease by environmental noise" [33] quantified the many health-related effects by long-term exposure to environmental noise. The positive influence of quiet urban areas, as a possible mitigating measure, has been shown before [34][35] [36] and has become part of European noise policy [37]. As a result, the sound environment in poten...

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Section: Computational Approachesmentioning

confidence: 99%

“…The FDTD implementation used here (see Ref. [56]) applies a lowest-ordered limited stencil approach, demanding a strong spatial and temporal discretisation. For accurate calculations, about 10 computational cells per wavelength are needed.…”

Section: Computational Approachesmentioning

confidence: 99%

The potential of building envelope greening to achieve quietness

Renterghem

Hornikx

Forssén

et al. 2013

Building and Environment

149

View full text Add to dashboard Cite

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“…which can be easily implemented in FDTD [14]. This means that for the ear canal the impedance of the ear canal'sw all is included [15] to model sound propagation in the outer ear and in addition the acoustics of the middle and inner ear are represented by the impedance at the eardrum [16].…”

Section: Simulations Of the Transfer Functionsmentioning

confidence: 99%

Digital Filters for Accurately Verifying the Performance of Hearing Protectors in Use

Bockstael¹,

Deschrijver²,

Botteldooren³

et al. 2010

Acta Acustica united with Acustica

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SummaryThe performance of hearing protectors can be assessed in situ by measuring the sound pressure inside the ear canal following the Microphone In Real Ear (MIRE)p rotocol. Thus acustom-made earplug has been designed with an inner bore, allowing the insertion of the MIRE measurement microphone. However, the actual exposure levelcan only be accurately predicted if the relationship, henceforth called transfer function, between the sound levelatthe microphone and at the eardrum is known. Previous research has revealed that the transfer function can be precisely approximated with an individualized FDTD model, butasimplified method is needed for practical implementation due to the time-consuming nature of this numerical technique. In this matter,aone-dimensional analytical model appears inadequate, hence an approximation to the detailed FDTD model based on digital filter design is proposed instead. Twod i ff erent approaches have been applied to estimate the individualized filter coefficients: multiple linear regression and Multivariate Orthonormal Ve ctor Fitting (MOVF).I ng eneral, both methods can predict an individual'st ransfer function quite accurately if the length of the earplug'si nner bore and the length of the residual part of the ear canal behind the protector are known. However, MOVF seems more reliable for ears with alonger residual part.

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“…In 1995, D. Botteldooren illustrates the use of a numerical time-domain simulation based on the FDTD approximation for studying low-and middle-frequency room acoustic problems [2]. After that, the application of FDTD in room acoustics had great progress in the boundary condition [3], near-to-far-field transformation method [4], and computational speed [5].…”

Section: Introductionmentioning

confidence: 99%

Underwater Broadband Acoustic Scattering Modelling Based on FDTD

Shao

Zhao

Xiangjun

et al. 2015

ElAEE

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Abstract-A modified finite-difference time-domain (FDTD) method is described in this paper. The absorption coefficient which is frequency-dependent is considered, and it is used to compute broadband acoustic scattering model of underwater complex object. The perfectly matched layer (PML) absorbing boundary condition (ABC) is applied to this work. Considering computation and accuracy comprehensively, PML boundary layer number and the attenuation coefficient is set at proper values. Computer Graphics are applied to mesh-generating of the irregular object. A pulse of LFM signal is used to simulate wide-band acoustic scattering field of a circle in 2D and a complex object in 3D. And the scattered acoustic pressure waveforms of some certain points are computed in the calculation field. Results obtained from simulation confirm the high accuracy of the proposed method.

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Finite-difference time-domain simulation of low-frequency room acoustic problems

Cited by 276 publications

References 0 publications

The potential of building envelope greening to achieve quietness

The potential of building envelope greening to achieve quietness

Digital Filters for Accurately Verifying the Performance of Hearing Protectors in Use

Underwater Broadband Acoustic Scattering Modelling Based on FDTD

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