publications

2023

1. 

   Acoustic Propagation in Forest Environments. Time domain numerical methods toward bioacoustic applications.

   Q. Goestchel

   Oct 2023

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   This manuscript investigates sound propagation modeling in forest environments, intending to understand the limitations ofexisting models and explore their potential bioacoustic applications. The subject is introduced by presenting current concernsabout the impact of noise on health and biodiversity. A literature review examines previous studies and existing outdoor soundpropagation models, both analytical and numerical, for their applicability to forest scenarios. Then, as a time-domain solver, theTransmission Line Matrix (TLM) model is thoroughly investigated, and the update of its theory allows for highlighting limitationswhen modeling outdoor long-range sound propagation. Numerical experiments are presented to quantify the subsequent errorsand limitations in the TLM model. The computational implications of modeling a significant number of points implied by largefrequency-distance ratios are discussed. Finally, some applications to model sound propagation within forests, with multipleimpedance boundary conditions, are presented, and a validation method is proposed through comparisons with in-situmeasurements at the Nouragues research station (French Guiana). Overall, this research contributes to the understanding ofhow to simulate sound propagation within forests and the potential practical applications that can arise from it.

   @phdthesis{Goestchel2023c,
     title = {Acoustic Propagation in Forest Environments. {{Time domain numerical methods}} toward {{bioacoustic applications}}.},
     author = {Goestchel, Q.},
     year = {2023},
     month = oct,
     langid = {english},
     url = {https://theses.hal.science/tel-04357383},
   }

2. 

   Transmission Line Matrix Model: Numerical Dispersion Effects on Simulated Specular Reflection [Under submission process]

   Q. Goestchel, G. Guillaume, D. Ecotière, and 1 more author

   Mar 2023

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   Numerical sound propagation models include a wide range of methods with their own advantages depending on the physical phenomena under consideration. Due to its low-order scheme characteristic, the transmission line matrix (TLM) model is considered for coarse modeling of sound fields in complex outdoor environments. However, the space-time integration scheme of the method is dispersive and affects the free-field predictions. This paper extends a previous study of the numerical dispersion effect on the acoustic pressure field. An ideal case with specular reflections on a perfectly reflective ground is considered to understand the limitations of the method. First, a reminder of the model boundary conditions for specular reflection is provided, and the corresponding analytical solution is introduced as a reference to evaluate the reliability of the model. Then, a numerical experiment is presented and performed for different sound source spectra. The result analysis shows that dispersion can induce misplaced interferences in the numerically simulated sound fields and the resulting errors are quantified in terms of sound pressure levels (SPL). Finally, an analytical comparison with a well-known finite difference numerical scheme gives a perspective on the TLM model performance regarding several applications.

2022

1. 

   Properties of the Transmission Line Matrix Model for Outdoor Sound Propagation: Numerical Dispersion Effects

   Q. Goestchel, G. Guillaume, David Ecotiere, and 1 more author

   In International Congress on Acoustics, Oct 2022

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   Time-domain numerical methods are attractive tools for the prediction of outdoor sound propagation as they are able to handle most of the physical phenomena involved in environmental acoustics. The transmission line matrix (TLM) method is considered for modelling sound fields in complex outdoor environments but it remains relatively poorly documented. In this paper, the space-time integration scheme of the method and a stability analysis are provided. The review of the model highlights similarities with a finite difference scheme and leads to a more robust understanding of its link with the wave equation using Taylor expansions. The stability analysis allows the numerical dispersion relation of the model to be formulated and the associated errors to be quantified. Two different numerical experiments are presented to characterize precisely the limitations of the method applied to outdoor sound propagation. To conclude, the results are analyzed, highlighting the effects of the propagation distance and the spectral distribution of the simulated sources.

2. 

   Analysis of the Numerical Properties of the Transmission Line Matrix Model for Outdoor Sound Propagation

   Q. Goestchel, G. Guillaume, D. Ecotière, and 1 more author

   Journal of Sound and Vibration, Aug 2022

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   Outdoor sound propagation modeling can be performed through various numerical models. Nowadays, time-domain methods are widely used and enable accurate simulations for most of the sound physical phenomena involved in environmental acoustics. However, the transmission line matrix (TLM) method remains relatively poorly documented. In this paper, a thorough review of the method and a stability analysis are provided. The review of the model leads to a more robust understanding of its link with the wave equation using Taylor expansions. Two different cases are considered: a homogeneous non-dissipative medium and an inhomogeneous dissipative one. The stability analysis shows the quantification of the model inherent dispersion error and highlights similarities with a finite difference scheme. To conclude, a numerical experiment aims to characterize precisely the limitations of the method applied to outdoor sound propagation.

2018

1. 

   The P.E.T. Comfort Index: Questioning the Model

   E. Walther, and Q. Goestchel

   Building and Environment, Jun 2018

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   [link to full text download on Elsevier https://authors.elsevier.com/a/1Wq~-1HudMvux8 (valid until May 25th 2018)] This work is a first thorough presentation of the widely used PET (Physiological Equivalent Temperature) comfort index. It underlines the simplifications made in solving the equation system for the PET and proposes a correction of the errors in the widespread version of the PET calculation routine. A comparison of the corrected model with a stringent solving of the equation system is made: as a result, the PET calculated after the original method introduces a bias of - 0.5 to + 2.3 [K] in the studied conditions (operative temperature, high mean radiant temperature and windy environments). The original vapour diffusion model is also examined and shows no dependency to the clothing level. The comparison with a state-of-the-art vapour transfer model exhibits a significant - 7 to + 2.6 [K] discrepancy with the corrected PET model in the aforementioned studied conditions. Links to the two versions of the code are provided in the appendix.