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

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 from outdoor spaces.

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 to model wave propagation in parallel or intersecting streets, [14–17] or in larger urban areas [18], but often limited to 2D geometries. Others have used a coupled modal-finite elements method to address the problem, while others have introduced the frontier finite elements method.
