Assessment of Speech Intelligibility in Buildings with Low Reverberation

This work is based on the results of listening tests designed through the comparison of two signals in order to investigate the subjective perception of speech intelligibility in public venues with low reverberation. Binaural impulse responses obtained in a campaign of acoustic measurements in a set of Roman theatres in Spain, built in the imperial era in what was then the province of Hispania, have been convolved with anechoic recordings of oral texts with male and female voices to produce the signals of comparison of the tests across the whole range of values of the acoustic parameter Speech Transmission Index (STI). This is a single-value parameter that integrates the significant spectral data of speech. These performance venues were built in classical times of Western civilisation for theatrical performances and other oral events where speech intelligibility played a primary role. They present short reverberation times at medium frequencies, between 0.33 s and 2.32 s, depending on the size and state of rehabilitation of the space. The tests were completed in a semi-anechoic acoustic laboratory in the School of Architecture of the University of Seville, and the design of the comparison pairs therein is based on the method of limits used in neuroscience. The statistical analysis of the results by means of Pearson's non-parametric chi-square test carried out by the SPSS software has been undertaken to study the correlations of the responses obtained; these correlations depend on whether it is the ascending or descending series of stimuli, and on the voice format, the gender, and sociological data of the respondents. Furthermore, an estimation is carried out of the differential limen of the STI parameter. The findings of this study are useful in the smart city context and urban planning, especially in public open-air venues.