ICSV17, Cairo, Egypt, 18-22 July 2010 1 ACOUSTICAL CHARACTERIZATION OF PORTUGUESE LIBRARIES António P. O. Carvalho, and António E. B. Costa Laboratory of Acoustics, Faculty of Engineering, University of Porto, R. Dr. Roberto Frias 4200-465 Porto, Portugal e-mail: carvalho@fe.up.pt This paper presents the acoustical characterization of the main reading room of 28 public li- braries in Portugal. In situ measurements were held regarding the interior sound pressure lev- els (background noise, with and without the HVAC equipment working), the Noise Criteria and Noise Rating values (NC/NR), the objective speech intelligibility using the Rapid Speech Transmission Index (RASTI) and Reverberation Time (125 to 4k Hz). Two groups of librar- ies were formed (Classic and Modern libraries) regarding their interior layout and date of construction and differences were checked. Regression models among the architectural and acoustical parameters were established. The acoustical performance of these spaces concern- ing the current Portuguese legislation is analyzed and a short set of design goals are presented to help acoustical consultants to achieve a good environment in this type of building. 1. Introduction The main reading rooms of public libraries are special places where the acoustics can be a very important matter. Low noise is a must. These spaces are characterized by a large open area, sometimes with a tall ceiling, and with walls and floor made with very sound reflective materials. The goal of this work was to check the overall acoustic conditions of these spaces by the use of objective acoustic parameters concerning their interior conditions: Reverberation Time (RT), Rapid Speech Transmission Index (RASTI), background sound levels and sound pressure levels of their HVAC equipment (and NC/NR noise curves). The among-room variations of acoustic objective parameters can be viewed as differences that result from the architectural proprieties of the rooms that experience shows actually exist. The hy- pothesis that Modern libraries have an acoustically different behavior than the older Classic librar- ies was tested.