The project of this thesis consists in several chronological stages: the first (July 2014) related classroom acoustics characterization. The second (November/December 2014) focused on teachers' voice monitoring over several working days during their teaching activity, and noise level measurements during lessons. During the third stage (February/March 2015) a seminar was held in each school for the students who would later completed the subjective questionnaires. The fourth stage (April/May 2015) consists in repeating the teachers' voice monitoring and noise level measurements in order to investigate if there are statistically significant differences in the parameters acquired at the beginning and at the end of the school year.

In-field measurements related sound insulation and room acoustics parameters. As far as sound insulation is concerned, the sound reduction index between adjacent and overlapped rooms, standardized noise level difference value of facade and maximum weighted standardized impact sound pressure level were measured in one in representative classroom in each school.

Room acoustical parameters were measured in occupied and unoccupied conditions for classrooms with different acoustical treatment in Avogadro institute, and for three classrooms with single, medium and double volume in Maxwell institute. Reverberation time and clarity were measured accordingly to the ISO 3382 standard using the B&K 4128 HaTS as a sound source. For clarity only one combination source-receiver position was considered.

Room gain and voice support were taken from literature and measured in two different positions in the room, while speech transmission index was measured considering the same source-receiver position assumed for clarity, with the indirect method reported in the IEC 60268-16.

Vocal load of teachers over several working days was monitored by means of the Voice-Care device, recently developed at the Politecnico di Torino. Mean and mode sound pressure level and fundamental frequency, as well as phonation time percentage were obtained for each teacher's monitoring.

Background noise was measured along the entire teachers' voice monitoring allowing the different teaching activities and subjects to be classified in terms of background noise level.

Surveys on the subjective impression of acoustical comfort in classrooms were administered to teachers and students. Subjective perception of teachers regarded noise disturbance, vocal effort and reverberation after each monitoring and averagely across the overall teaching period. Students were asked to rate subjective impressions on noise disturbance, teachers' vocal effort, reverberation, speech intelligibility and overall acoustical quality. All the objective data (acoustics characteristics, teachers' vocal effort and background noise level) are in this thesis analyzed in relation with the subjective data using statistical tools.

The objective of this thesis is the investigation of the relations between objective and subjective perception of acoustic conditions in high school classrooms. In particular, the level of noise measured in different environments during different activities, the vocal effort of teachers, the subjective impression of teachers and students and the physical and acoustical characteristics of classrooms are hereby put in relation.

The outcomes of this analysis are willing to help in the definition of new acoustical requirements for classrooms design, in particular for integration with the existing protocols such as LEED for SCHOOL. The minimum requirements, indeed, now only refer to sound absorption and reduction of noise level. It would therefore be appreciable to add enhanced requirements referred to subjective parameters in relation to objectively measured parameters. This would help in the design of school environments that ensure a high level of teaching and learning quality for both students and teachers.