Computation of edge diffraction for more accurate room acoustics auralization

Abstract

Inaccuracies in computation and auralization of room impulse responses are related in part to inadequate modeling of edge diffraction, i.e., the scattering from edges of finite surfaces. A validated time-domain model (based on analytical extensions to the Biot-Tolstoy-Medwin technique) is thus employed here to compute early room impulse responses with edge diffraction. Furthermore, the computations are extended to include combinations of specular and diffracted paths in the example problem of a stage-house. These combinations constitute a significant component of the total nonspecular scattering and also help to identify edge diffraction in measured impulse responses. The computed impulse responses are then convolved with anechoic signals with a variety of time-frequency characteristics. Initial listening tests with varying orders and combinations of diffraction suggest that (1) depending on the input signal, the diffraction contributions can be clearly audible even in nonshadow zones for this conservative open geometry and (2) second-order diffraction to nonshadowed receivers can often be neglected. Finally, a practical implementation for binaural simulation is proposed, based on the singular behavior of edge diffraction along the least-time path for a given source-edge-receiver orientation. This study thus provides a first major step toward computing edge diffraction for more accurate room acoustics auralization.

Modeling acoustics in virtual environments using the uniform theory of diffraction

“…The accuracy would be improved, especially at low frequencies and near-field from the wedges. Also, as mentioned in [41], the shortest paths constructed by our technique would still be useful for efficient auralization even if the diffraction coefficients (or filters) are derived from another theory. The left-most column shows beams (cyan) traced from a source point.…”

“…In this case, the edges are discretized into secondary point sources whose contributions must be summed to obtain the diffracted field. Such models prove very accurate for low order diffraction and have recently been used to assess audibility of diffraction in the case of a simple stage house [41]. However, it is unclear if the method can be applied in real-time since the edges must be discretized into a large number of point sources to compute the diffraction filters.…”

“…Recent psychoacoustic tests in the context of a simple stage house model [41] show that diffractions can be perceived in illuminated regions where direct and reflected contributions from a source also reach the listener. However, in this case, we conjecture that diffraction does not modify the main acoustic cues already carried by the direct and reflected contributions since the amplitude of the diffracted field is usually much weaker than direct or even reflected contributions [31] (p.500).…”

Simulated Sound-Fields in a Multi-Configurable Auditorium

“…Nowadays, the wide range of existing commercial computer programmes, whose validity can be directed towards a variety of scientific aspects (Ermann, 2005;Rychtáriková et al, 2011), incorporate highquality auralizations. A major effort is being invested in research for the refinement of these auralizations (Torres et al, 2001;Calamia et al, 2008; Zahorik, 2009) in acoustic virtual-reality applications, and for the recreation of the sound of both multiple future virtual acoustic environments of spaces and of ancient scenarios for archaeological purposes (Vassilantonopoulos, Mourjopoulos, 2009).…”

Contribución a la simulación virtual de parámetros de calidad acústica en espacios arquitectónicos. Aplicación del método de superficies de respuesta

“…Al aumentar la potencia de los procesadores, el número de rayos susceptibles de ser calculados aumenta exponencialmente, de forma que la difusión cobra relevancia. En una primera etapa se estudia la difusión producida en las aristas [30], añadiendo a los modelos mayor realidad en el cálculo de las reflexiones. Como comprobación se realizan pruebas en espacios controlados, obteniendo como resultados que los modelos difusos (con la difusión de los rayos mejor calculada) dan como resultados valores más exactos [31].…”