**1.2. Spatial audio in architectural representation**

experience? It seems practically impossible to imagine an evaluation of cultural resources that is only based on abstract concepts. However, the evaluation also requires a common basis to enable comparisons of the results. This second answer supports the immersive experience as

An explanation is required to understand the methodology used in this paper. In general, people know very little about decibels of sound, and much less about sound roughness, musical clarity or speech intelligibility. Only a small group of scientists understand the operation of acoustic science. Therefore, when urban acoustic heritage is evaluated, why are ordinary people forced to refer to numbers and graphs? Surely the evaluation would be more reasonable if it were made using real sound samples? In this context, Virtual Reality (VR) provides an easy, interactive framework for ordinary people to evaluate urban acoustic heritage.

The interest in conservation of tangible and intangible cultural heritage has been rising notably in recent years. Apart from its own value, cultural heritage fosters economic and social growth. The Heritage Research National Plan, drawn up by the Spanish Cultural Heritage Institute, highlights the importance of cultural heritage as a local development engine and a stimulus for tourism, and its relevance as a generator of culture and knowledge. However, the Plan also stresses the complexity of research in this field, due to a range of characteristics and problems, and because of the high number of factors involved that make it necessary to apply

The evaluation of the acoustic quality of a space is fundamental to determine possible interventions in it and the suitability of its future uses. Several studies have established optimal indexes and ranges for the various measurable parameters [2, 3]. Nevertheless, as in current regulations, the focus has been concert halls, which have different features and requirements

Very few objective and subjective tests have been undertaken in these kinds of spaces, due to the difficulty in installing measuring instruments and the variable conditions of the environments. In this study, four outdoor spaces were tested and a great effort was made to find the best environmental conditions. Preliminary work was done in the studied environments [4]. The application of new technologies in cultural heritage is a practice that has become increasingly widespread. The construction of virtual models allows us to reproduce environments for their study, avoiding direct intervention in these spaces and encouraging their conservation. After some data collection in the actual place, a model is designed and calibrated in which the environment can be recreated as many times as desired, without the need to travel there. This

methodology could overcome the major difficulty that an in-place test might present.

Some authors have attempted to investigate urban sound propagation. They have centered on the complexity of the medium: irregular faces, interconnection with adjacent canyons, and a large variety of materials and boundary conditions. Moreover, a predominant characteristic of the urban environment is that it is open to the sky, and induces large radiative losses [5–7]. Much of the literature is focused on propagation in a single urban canyon [8–13]. A few authors attempted

a powerful method for cultural resources evaluation.

44 From Natural to Artificial Intelligence - Algorithms and Applications

human and experimental sciences in interdisciplinary teams.

**1.1. Evaluation of acoustic quality in outdoor spaces**

from outdoor spaces.

Spatial audio in virtual reality has received increasing attention in recent years, due to its impact on the immersive experience. Spatial audio is the representation of audio features of reality that intentionally exploit sound localization. It has many possible uses in the gaming industry, entertainment or military applications. Most of these uses rely on both acoustic and spatial information about the sound. However, although spatial information is addressed, architectural design representation does not currently pay much attention to spatial audio as a factor in spatial representation.

Many other factors that have been considered in architectural design representation are linked to visual features [19, 20]. Natural light modeling and rendering [21, 22], artificial light control [23, 24], texture cognition and representation [25, 26], color discernment [27, 28] or material visualisation [29–34] are some of the countless details that an architect must manage when they represent a building. However, although the effect of sound on spatial cognition is recognizable [35], it has received little attention in architectural representation.

In 2003, Kang et al. highlighted the introduction of new EU noise policies [36] and noted that noise-mapping software/techniques are being widely used in European cities [37]. Nevertheless, they noted that these techniques can provide an overall picture for macro-scale urban areas, but the study of the micro-scale, for example an urban street or a square, could be more appropriate with the use of detailed acoustic simulation techniques. In addition, applications that predict and measure micro-scale environments [38] are still not sufficiently user-friendly, and the computation time is rather long. Kang et al. presented two computer models based on the radiosity and image source methods in an attempt to present to urban designers an interface that could be useful in the design stage, using simple formulae that can estimate sound propagation in micro-scale urban areas.

This paper presents a set of criteria for implementing 3D audio in virtual urban environments. The study is based on the definition of a new virtual audio format, generated from the combination of objects and ambisonic formats. This new audio format was explained in 2017 [4]. Using these criteria, we then describe the preparation of a set of experiments with architecture students. The results of the experiments confirm that the implementation of 3D audio enhances the immersive experience in the environments.
