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Combined effects of noise and room acoustics on voice production in simulated classrooms

Marcella Cipriano

Combined effects of noise and room acoustics on voice production in simulated classrooms.

Rel. Arianna Astolfi, David Pelegrín García. Politecnico di Torino, Corso di laurea magistrale in Architettura Costruzione Città, 2015

Abstract:

This work concerns the relationship of the two main factors, namely the room acoustics and background noise, with the vocal effort. Teachers and non-teachers have been invited to perform talking test under simulated classroom acoustic conditions of varying levels of speech shaped noise in order to understand this relationship. At the same time their subjective preference of teaching in classrooms by means of questionnaires has allowed refining guidelines for classroom acoustic design. Under simulated acoustic environments, talkers distort their voice linearly dependent on the voice support on maximum noise level, and the slope of this relationship is defined as room effect. The magnitude of the room effect depends highly on the Lombard effect, i.e. the vocal effort as function of the noise above a set level of 45 dB .In fact, the average room effect ranges from -0.10 dB/dBs, with the lowest noise level numerically assigned to 0 dB (variable though much lower than medium noise level of 50 dB), of -0.11 dB/dBs with noisier condition of the 50 db, to -0.24 dB/dBs with louder background noise of 62 dB. The trend room effect as function of noise level showed an optimal classroom acoustics as best auditory feedback about the minimum voice level achieved. It has values of voice support STv around -6.1 dB and of the Decay time DT40ME around 1.10 s. The subjective data concerning the perception of general comfort,( reverberance of the room and noise feeling after questionnaire replies) showed that the acoustic comfort as well as the noise, is linearly related to the perception of noise and is not related to the room acoustics.
Relatori: Arianna Astolfi, David Pelegrín García
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 > SH Fisica tecnica
Corso di laurea: Corso di laurea magistrale in Architettura Costruzione Città
Classe di laurea: NON SPECIFICATO
Aziende collaboratrici: NON SPECIFICATO
URI: http://webthesis.biblio.polito.it/id/eprint/4494
Capitoli:

Introduction

1. Room acoustics parameters for speaker

1.1. Voice support STV

1.1.1. Relation with voice

1.1.1.1. Vocal Effort and Lombard effect

1.2 Decay time DT40,ME

1.1.2. Relation with voice

2. Experimental method

2.1 Measurements

2.1.1 IRs measurements

2.1.1.1 Elements of the setup

2.1.1.2 Measuring conditions

2.1.1.3 During the session

2.1.1.4 Results

2.1.2 OBRIRs measurements

2.1.2.1 Elements of the setup

2.1.2.2 System setting

2.1.2.3 Measurements

2.1.2.4 Post-processing

2.1.2.5 Results

2.2 Acoustic Virtual Reality(AVR) System

2.2.1 System overview

2.2.2 Simulation

2.2.3 Adding data into the AVR system

2.2.4 Background noise levels

2.3 Talking test

2.3.1 Setup

2.3.2 Conditions

2.3.3 Subjects

2.3.4 Instructions

2.3.5 Post-processing of the speech signals

2.4 Questionnaire

3. Statistical analysis

3.1 Voice level

3.1.1 Room effect

3.1.2 Lombard effect

3.2 Subjective data

4. Results

4.1 Voice level

4.1.1 Room effect

4.1.2 Lombard effect

4.2 Subjective data

4.2.1 Comfort

4.2.2 Reverberation

4.2.3 Noise

5. Discussion

5.1 Voice level

5.1.1 Room effect

5.1.2 Lombard effect

5.2 Subjective attributes

Conclusion

Ackowledgments

References

APPENDIX A: IRs measurements

A.1 IRs measurements results

APPENDIX B: OBRIRs measurements

B.1 OBRIRs measurements results

APPENDIX C: Experimental method

C.1 Talking test-Example map route

C.2 Questionnaire

APPENDIX D: Results

D.1 Room effect

D.2 Lombard effect

D.3 Subjective data

Bibliografia:

References

- D. Pelegrin-Garcia, J.Brunskog, "Speakers' comfort and voice level variation in classrooms," Laboratory research. J. Acoust. Soc. Am. 132 (2012) 249-260.

- ISO 9921, Ergonomics - Assessment of speech communication, International Organization for Standardization, Genève, 2003.

- A. Astolfi, P. Bottalico, G. Barbato: Subjective and Objective speech intelligibility investigations in primary school classrooms. J. Acoust. Soc. Am. 123 (1012) 247-257.

- D. Pelegrin-Garcia, J. Brunskog, and B. Rasmussen, “Speaker-oriented classroom acoustics design guidelines in the context of current regulations in European countries,” Acta Acustica United with Acustica. In Press (2014)

- H. Lane, B. Tranel: The Lombard sign and the role of hearing in speech, J. Speech Lang. Hear. Res. 14(1971)677-709.

- D. Pelegrin-Garcia: Acoustic Virtual Reality System, User manual for tests and measurements + administrator guide. Laboratory of acoustics, Augusts 2015.

- prEN ISO 3382-2: 2003, Acoustic - Measurement of the reverberation time - Part 2: Ordinary rooms.

- Ian R. Cushing, Francis F. Li, Trevor J. Cox, Ken Worrall, Tim Jackson: Vocal effort levels in anechoic conditions, Applied Acoustics 72 (2011) 695-701.

- W. Navidi: Statistics for Engineers and Scientists, third edition, McGraw-Hill, New York 2009.(322-329)

- J. Brunskog, A. Gade, G. P. Ballester, L. R. Calbo: Increase in voice level and speaker comfort in lecture rooms. J. Acoust. Soc. Am. 125 (2009) 2072-2082

- D. Pelegrin-Garcia: Comment on Increase in voice level and speaker comfort in lecture rooms [J. Acoust. Soc. Am. 125 (2009) 2072-2082] J. Acoust. Soc. Am. 129 (2011) 1161-1164.

- McCallum Layton-Statistical calculator - https://www.mccallum-layton.co.uk/
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