# Historically Based Room Acoustic Analysis and Auralization of a Church in the 1470s
## 1 Introduction  
The acoustics of worship spaces are a significant element of a nation's cultural heritage. The concept of cultural heritage is described by UNESCO as  
\"those sites, objects and intangible things that have cultural, historical, aesthetic, archaeological, scientific, ethnological or anthropological value to groups and individuals\" [1]. Since UNESCO's adoption of the _Convention for the Safeguarding of the Intangible Cultural Heritage_[2] in 2003, the acoustics and acoustical experiences of churches have been established as an important area of research. The interaction between ritualistic and cultural expressions in churches and their acoustics have been the topic of several research projects [3, 4, 5, 6, 7, 8, 9, 10]. The comprehensive review article on church acoustics by [PERSON] et al. [11] discusses the efforts of several research teams who have acoustically characterized a large number of churches across the world and, specifically, Europe. Most of this research has focused on churches located in countries around the Mediterranean sea, resulting in less scientific literature regarding churches in northern Europe. While Polish researchers have made interesting analyses on some churches around the Baltic Sea [12, 13] and there is research on some Russian churches [14], there is very little, ifany, acoustic research on religious buildings in Scandinavia and, specifically, Sweden. The research presented in this paper sheds new light on intangible cultural heritage in this part of the world by presenting a room acoustic analysis on a digital reconstruction of Vadstena abbey church in Sweden. This work is part of a larger research project [15]. Such _archaeoucoustical_[16] projects, where acoustic simulations in digital reconstructions of historical spaces are performed, have already been undertaken [17; 18; 19; 20; 21]. The results of these projects may be combined with visual models to produce Virtual Reality experiences, which has been done by several teams [22; 23; 24] and is the goal of this project. Efforts such as these require a tight collaboration between acousticians, 3D artists, historians, and musicologists to tackle the intrinsic multidisciplinary nature of the research. The large amount of heritage objects not yet investigated with such techniques, the relative novelty of the underlying technologies, and the challenges posed by such collaborations motivates further research projects such as the one reported on in this paper. The combination of archaeoacoustic modeling and visual models often requires some form of _auralization_. Auralization can be defined as \"... the process of rendering audible, by physical or mathematical modeling, the soundfield of a source in a space, in such a way as to simulate the binaural listening experience at a given position in the modeled space\" [25]. Application and implementation of auralization is in itself a large research area [26; 27; 28]. Although auralized audio samples are presented in this paper, the main focus is placed on the development of the 3D model, and on the room acoustic analysis. A foundational course in auralization can be found in [29]. Liturgical practices are characterized by significant auditory elements, such as prayers, chants, or preaching. Understanding of these practices and how they function within a church benefits from room acoustic analyses of churches. Such analyses are based on room acoustic parameters typically computed from impulse responses, which can be estimated using acoustic simulation software. For example, the perception of chant is strongly related to early reverberation [4], and the intelligibility of song and speech can be related to clarity parameters. As within any volume, room acoustic parameters in a church may have a weaker or stronger spatial dependence. Spatial variations of room acoustic parameters within churches depend partly on varying materials and partly on varying geometry.