Comparative study of two geometrical acoustic simulation models

Abstract

Simulations based on the concepts of geometrical acoustics are today well-established tools for acousticians, being widely used for evaluation of sound quality in rooms and urban spaces. However, although a lot of different models are available and have been evaluated in the past, it is still very important to guarantee the validity and quality of simulated data and reproduced sound. This work presents a comparison between the signal processing strategies in two acoustic simulators based on geometrical models. Obvious expectation was that both simulators would produce the same results when fed by exactly the same input data. However, issues related to model assumptions, propagation methods characteristics and signal processing techniques adopted by each simulator introduce differences which alter the final results, i.e., the simulated acoustic impulse responses. This papers aims to present such deviation and helps to understand the influence of each component over the results. Firstly, both simulators are described in detail, presenting their acoustic models and the signal processing approaches. In addition, an extensive analysis of early reflections is performed, considering pressure levels, reflection order, their arrival time and directional characteristics. Next, simulated energy decay curves, monaural room acoustic parameters and spectra are objectively compared to measured data of a reverberant chamber, in two different conditions. The differences are then pointed out and minimized by unifying the signal processing of both simulators. The results of this comparison reveal that signal processing and inherit method characteristics still have strong influence over the simulated impulse responses, mainly for the late part. Some consequences are energy misbalance between early and late parts of impulse response, leading to differences over the room acoustic parameters, mainly clarity and definition.

Assessing acoustical quality in university classrooms in Brazil: Measurements and simulations

“…The efficiency of RAVEN was highlighted for several researches. 27 –31 RAVEN is available under request for the Institute of Technical Acoustics (ITA), and I-SIMPA is an open-source software developed by Gustave Eiffel University. 32,33…”

“…The efficiency of RAVEN was highlighted for several researches. [27][28][29][30][31] RAVEN is available under request for the Institute of Technical Acoustics (ITA), and I-SIMPA is an open-source software developed by Gustave Eiffel University. 32,33 Sound absorption and scattering coefficients are shown by Tables 4 and 5, provided by Vorländer.…”

Acoustical Evaluation of the Itacuruçá Baptist Evangelical Church

“…In order to evaluate the effect of material changes and the inclusion of absorptive surfaces, the acoustic simulator BRASS (Brazilian Room Acoustic Simulator) was selected for the task [35][36][37]. BRASS is a simulation tool that generates impulse responses (pressure over time) based on the ray-tracing method [38].…”

Simulações de Acústica de Salas desenvolvidas nas universidades do Brasil

“…No site www.lisa.poli.ufrj.br/brass é possível baixar a versão de demonstração, que possui apenas restrições na quantidade máxima de planos, fontes e receptores simultâneos, juntamente com o manual de utilização. Maiores detalhes sobre a implementação podem ser obtidos em Torres et al[39,40].…”