Worship space acoustics have been established as an important part of a nation’s cultural heritage and area of acoustic research, but more research is needed regarding the region of northern Europe. This paper describes the historical acoustics of an important abbey church in Sweden in the 1470s. A digital historical reconstruction is developed. Liturgical material specific to this location is recorded and auralized within the digital reconstruction, and a room acoustic analysis is performed. The analysis is guided by liturgical practices in the church and the monastic order connected to it. It is found that the historical sound field in the church is characterized by the existence of two distinct acoustical subspaces within it, each corresponding to a location dedicated to the daily services of the monastical congregations. The subspaces show significantly better acoustic conditions for liturgical activities compared to the nave, which is very reverberant under the conditions of daily services. Acoustic transmission from the two subspaces is limited, indicating that the monastic congregations were visually and acoustically separated from the visitors in the nave and each other. These phenomena can be heard in the auralizations, which are presented as supplementary material.

Raytracing is a widespread tool for room acoustic simulations, and one of its main advantages is the inclusion of surface scattering. Although surface scattering has been acknowledged as a central aspect of accurate raytracing simulations for many years, there is ongoing research into its effects and how to implement it better. This study evaluates three different algorithms for surface scattering in raytracers, referred to as on–off scattering, perturbation scattering, and diffuse field scattering. Their theoretical foundation is discussed, and the physical accuracy of the resulting simulations is evaluated by comparing simulated room acoustic parameters to measurements. It is found that the choice of surface scattering algorithm has a significant impact on the simulation outcomes, both in terms of physical accuracy and in terms of usability. Additionally, there are differences in the parametrization of surface scattering depending on the algorithm chosen. Of the three tested algorithms, the most commonly used algorithm (on–off scattering) seems to have the best properties for simulations.

Ray tracing is a frequently used method for acoustic simulations, valued for its calculation speed and ease of use. Although it is fast, there are no fully ray tracing-based real-time simulation methods or engines. Under real-time restrictions, ray tracing simulations lose precision and the variance inherent in the random simulation method has too much impact on the outcome. In this paper, an algorithm called iterative ray tracing is presented that reduces the negative effects of real-time restrictions by iteratively improving the initial calculation and increasing the precision over time. In addition, new estimates of the expected value and variance of ray tracing simulations are presented and used to show the iteration steps in the new algorithm reduce variance, while maintaining the expected value. Simulations using iterative ray tracing are compared to measurements and simulations using the classical ray tracing method, and it is shown that iterative ray tracing can be used to improve precision over time. Although more testing is needed, iterative ray tracing can be used to extend most ray tracing algorithms, in order to decrease the adverse effects of real-time restrictions.

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