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Prevision of optimal speech intelligibility in primary school classrooms through simulation of optimal acoustic absorption and diffusion conditions

Bolognesi, Filippo

Prevision of optimal speech intelligibility in primary school classrooms through simulation of optimal acoustic absorption and diffusion conditions.

Rel. Arianna Astolfi, Birger Kollmeier, Giuseppina Emma Puglisi, Louena Shtrepi, Anna Warzybok. Politecnico di Torino, Corso di laurea magistrale in Architettura Costruzione Città, 2016

Questa è la versione più aggiornata di questo documento.

Abstract:

Speech communication is a so natural action that it is easy to understimate the incredible difficulties our auditory system has to overcome in order to extract meaningful information from the complex auditory signals entering our ears. There are different types of environments in which obstacles to our sound perception may be various, however our auditory system’s capacities are particularly stretched to the limit in environments where we try to understand one talker among multiple people speaking at the same time. Natural speech, with its voiced phonemes that show large variations in fundamental frequency across talkers rapidly alternating with unvoiced phonemes, does not represent the best acoustic signal for communication and it severely tests our brain abilities in extrapolating information among all the interferences. This is the reason why good acoustics, in environments where speech is particularly important, must be correctly provided.

Speech intelligibility refers to the “understandability” of speech, the match between the intention of the speaker and the response of the listener, and the ability to use speech to communicate effectively in everyday situations. An existing study, deepened the pro¬babilities of occurrence of correct and partially correct responses. It has been estimated that, for speech masked by noise, the probability of recovering a missing phoneme is approximately 50% for meaningful words and 20% for nonsense words. Words missing from short everyday sentences can be filled in more easily with 70-90% accuracy, depending on sentence length.

Aim of this thesis is to investigate how architecture and room design can help in diffe¬rent aspects of human listening activities and what could be the solutions to optimize the signal comprehension in environments where the clarity of communication has to be the fundamental aspect: school classrooms.

Section 1 holds the main aspects of sound both as a physical phenomenon and as he¬aring sensation after passing our human auditory system. How sound is perceived and what are the main parameters that are going to be used in the experimental steps.

In the second section there are the main principíeos of rooms’ acoustics and some general advices to correctly design schools; how noise and reverberation have to be controled in order to not compromise the quality of teaching activities.

The last section of this thesis analyzes the experimentation led in Oldenburg from Mar¬ch to July 2016, at the Carl von Ossietzky Universität. Sound quality has been studied through the virtual simulation of classrooms and the research of the best improvement considering situations where students have to correctly understand the teaacher spea¬king while sourrounded by noise sources in other positions of the classroom.

Relatori: Arianna Astolfi, Birger Kollmeier, Giuseppina Emma Puglisi, Louena Shtrepi, Anna Warzybok
Tipo di pubblicazione: A stampa
Soggetti: A Architettura > AL Edifici e attrezzature per l'istruzione, la ricerca scientifica, l'informazione
S Scienze e Scienze Applicate > SA Acustica
S Scienze e Scienze Applicate > SH Fisica tecnica
Corso di laurea: Corso di laurea magistrale in Architettura Costruzione Città
Classe di laurea: Nuovo ordinamento > Laurea magistrale > LM-04 - ARCHITETTURA E INGEGNERIA EDILE-ARCHITETTURA
Aziende collaboratrici: Universität Oldenburg, Universität Oldenburg
URI: http://webthesis.biblio.polito.it/id/eprint/4918
Capitoli:

SECTION 1 - STARTING CONCEPTS

1.1 SOUND AS PHYSICAL PHENOMENON

1.1.1 SOUND AND SOURCES

1.2 PARAMETERS

1.2.1 REVERBERATION TIME

1.2.2 CLARITY

1.2.3 DEFINITION

1.2.4 EARLY DECAY TIME

1.2.5 SIGNAL-TO-NOISE RATIO

1.2.6 SPEECH TRANSMISSION INDEX

1.2.7 EQUIVALENT NOISE LEVEL

1.3 ACOUSTICS AS AN INTERDISCIPLINARY SCIENCE

1.4 LISTENING TASK

1.4.1 HUMAN HEARING SYSTEM

1.4.2 SOUND PERCEPTION

1.4.3 SPEECH INTELLIGIBILITY AND LISTENING EFFORT

1.4.4 COCKTAIL PARTY PHENOMENON

1.4.5 ADVANTAGES FROM BINAURAL LISTENING

SECTION2 - ACOUSTIC COMFORT

2.1 ACOUSTICS IN TEACHING ENVIRONMETS

2.1.1 SOURCES OF NOISE AND RELATED EFFECTS

2.1.2 VOCAL EFFORT AND RELATED ILLNESSES

2.2 ACOUSTIC REQUIREMENTS

2.2.1 LEGISLATION

2.3 DESIGN SOLUTIONS TO CONTROL NOISE

2.3.1 CONTROL OF EXTERNAL NOISES

2.3.2 CONTROL OF INTERNAL NOISES

2.3.3 ACOUSTIC BRIDGES AND INSTALLATIONS

2.4 DESIGN SOLUTIONS TO CONTROL REVERBERATION

2.4.1 SOLUTIONS AND MATERIALS FOR SOUND ABSORPTION

SECTION 3 - EXPERIMENTATION

3.1 COOPERATION WORK WITH OLDENBURG

3.2 RESEARCH PROPOSALS

3.2.1 CASE STUDY AND FEATURES

3.2.2 ROOM A

3.2.3 ROOM B

3.2.4 INVESTIGATION

3.2.5 CONFIGURATIONS

3.3 STEP ONE: LISTENING TEST

3.3.1 THE MATRIX SENTENCE TEST

3.3.2 SETTINGS

3.3.3 TEST RESULTS

3.4 STEP TWO: MODEL CALIBRATION

3.4.1 DIGITAL MODELS FOR REAL CLASSROOMS

3.4.2 SURFACES' PROPERTIES

3.4.3 CALIBRATION RESULTS

3.4.4 COMMENTS ON CALIBRATION

3.5 STEP THREE: ACOUSTIC DESIGN

3.5.1 FLAWS IN COMMON TREATMENTS

3.5.2 ANALYSIS SPECIFICATIONS

3.5.3 THE DIFFUSING PANEL ON THE LOWER FRONT WALL: COMPARISONS

THE LAST RAW OF SEATS

3.5.4 TOWARDS THE BEST IMPROVEMENT

CHOSEN CONFIGURATION

3.6 STEP FOUR: INTELLIGIBILITY PREDICTION

3.6.1 BSIM: A MODEL TO PREDICT INTELLIGIBILITY

3.6.2 BSIM PREDICTION IN THE ROOM BEFORE TREATMENT

3.6.3 BSIM PREDICTION IN THE ROOM AFTER TREATMENT

CONCLUSION

APPENDIX A

APPENDIX B

BIBLIOGRAPHY

ACKNOWLEDGMENTS

Bibliografia:

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