**2.1. Plaça Sant Felip Neri**

This quiet and secluded public square, located at the end of Montjuïc del Bisbe street, is one of a set of closed squares in the Ciutat Vella of Barcelona. Its floor plan shows an irregular pentagon boundary figure with a central fountain. The 505 sqm plan presents a uniform stone floor material and is completed by five façades made of stone material as well. Of the five façades, one is Sant Felip Neri church, while the others house a school, a hotel, some dwellings and the parish stances. Three big, old trees with an asymmetric distribution in plan cover the square with their foliage. Their trunks serve as irregular columns that support the green ceiling, enclosing the square and preventing people from seeing the open sky. No sound of traffic is heard, because the Plaça is far from main roads. However, the noise of shouting children fills the square every morning, when a group play during breaktime in their beautiful schoolyard: Plaça Sant Felip Neri. During the rest of the day, a few groups of tourists arrive and look to the pockmarked stones on the church façade; marks that remind us of the Spanish Civil War. At any time of day, a street musician may use the square to play the guitar or violin in the most distant corner or near the central fountain, accompanying with music couples who are out walking, in a romantic scene.

**2.4. Plaça del Rei**

of 12,000 m3

environment, as shown in **Figure 3**:

Some meters behind Plaça de Sant Iu is Plaça del Rei, a totally different environment both in size and proportions. There are no trees in this 745 sqm area of stone pavement, whilst its four façades enclose the square up to a height of 20 m. In the north corner of the square, a monumental staircase rises from the floor to the Museu de la Ciutat door. Usually, street musicians enliven the atmosphere with their instruments every day, and crowds of tourists occupy the entire square looking at the real shields on the walls, the pointed arches of the windows, or the tower of Santa Àgata chapel. The everyday life of the square is always very busy, and total silence only occurs when the square transforms into a concert hall for choir, orchestra or band performances. At these times, the players are usually situated on the corner stairs and the public occupy the rest of the square. When this happens, the sound of the musicians can be heard bouncing on the hard

Evaluation between Virtual Acoustic Model and Real Acoustic Scenarios for Urban Representation

http://dx.doi.org/10.5772/intechopen.78330

47

The four environments have some features of open-air places. However, bearing in mind studies on the evaluation of outdoor space acoustics [39], we analysed them using a closed concert hall acoustic method. This decision was taken after considering three factors. The first concerns the openness of the places: the four environments can be seen as boxes in which the floor and walls are made of stone, and the ceiling of the most absorbent material that ever existed, because no sound will bounce in the open air. The second consideration for the decision concerns size: the

it similar to a typical hall for speeches; the largest environment, the Plaça del Rei with a volume

Concert Hall. Finally, the third consideration explains that in an open-air environment, the sound sources change their position every moment. This situation could be definitive if we were studying the soundscape of an everyday configuration, with running children, singers, street vendors or even police sirens. However, we are recording the place in a street concert configuration, and this means that there is one player at a fixed point and the listeners stand up in the quietest mode. The measurement methodology was *previous controlled reproduction.* This method consists of the previous recording of an acoustic signal in an anechoic chamber and the following recording of the same signal in the environment. Subsequently, the two signals are compared. The first of the recordings in the anechoic chamber were made with a calibrated reproduction system and a calibrated recording system. The reproduction system consisted of a directional speaker LD 90 W connected to a 230 V power supply. It was positioned in one of the corners of the anechoic chamber. The recording system consisted of RODE NT-55 pair-matched microphones connected to a ZOOM H6 handy recorder on a stand. This recording system was positioned in the middle of the chamber, which was 2.5 m from the speaker. Additionally, the anechoic measurements were recorded with a HATS system connected to a laptop (**Figures 1** and **2**).

The in-site measurements were performed with the same equipment as the anechoic chamber measurements, except the HATS system. The distance of the measurements varied in each

, does not exceed the volume of a big concert hall such as the Berlin Philharmonic

, which makes

stone of the rear walls creating a sense of spatiality that envelopes the audience.

smallest environment, the Carrer de Santa Llúcia, holds an air volume of 1800 m3

**3. The methodology used for the in-site measurements**
