The church of Santa Ana in Moratalaz, Madrid, Spain (1965-1971), is an emblematic work of the architect Miguel Fisac. In his long career include interventions in the religious field, constituting one of the most important contributions to Spanish religious architecture of the last century. This church is a singular place of worship and architecturally significant, in which the acoustics played an important role in the configuration of the spatiality of the church. This paper studies the acoustic behaviour of the church and its relationship with its unique structural, spatial and coating material characteristics. The analysis of the current acoustic conditions, with high reverberation times (up to 6 seconds) and poor intelligibility on the audience, serve as the basis for making an acoustic rehabilitation proposal that contributes to improving the sound conditions of the building for the intended use, without distorting the spatial, formal and material aspects with which the architect conceived the project.

Several authors have proposed indices to synthesize the acoustics of a space, especially of concert halls. Meanwhile, a few studies have focused on the acoustics of worship spaces. The peculiarities of these last ones have shown distinctive characteristics. The increasing interest for the acoustics of worship spaces justifies the formulation of indices to synthesize the results of acoustic studies in these buildings too. This paper proposes a double synthetic index to evaluate the acoustics of a church. The index is obtained combining the average values of seven parameters generally considered in studies of architectural acoustics. The differences between requirements for music and speech in churches suggest to consider different optimal values of the selected parameters for different kinds of sound. A double synthetic index has been defined to synthesize the acoustical properties related to the music and to the speech separately. The validity of this double index is then assessed, comparing its values with subjective preferences captured through listening tests. The index, which is proposed and validated in this paper, aims to be an instrument to show synthetically the acoustical characteristics of a church to people with low knowledge in acoustics.

The church of Santa Cruz de Oleiros, Spain (1967) shows architect Miguel Fisac’s perception of sacred space after the Second Vatican Council. In this place of worship, the architect responded to the new liturgical guidelines combining geometry and architectural forms with the material of the moment, concrete. However, ordinary religious celebrations reveal acoustic deficiencies for the main use of the building. This fact is corroborated by acoustic measurements in situ. With a methodology that uses simulation techniques for the sound field, the analysis of the current acoustic behaviour of the room will serve as the basis for an acoustic rehabilitation proposal aimed at improving the acoustic conditions and so, the functionality of the church.