Figure 18: The relative effect of noise and room acoustics on the used voice levels

The estimated causes of the voice regulation are shown in Fig. 19, in terms of VL variation as a

function of STV when background noise is not present. The estimation is taken from the slopes of

the room gain (G

_RG

) – VL characteristic in the laboratory experiments in subprojects B1-3. In real

classrooms, the slope is -13.5 dB/dB (Pelegrín-García, D., 2011). If the distance effect is removed,

the adjustment is -3.6 dB/dB. From this amount, -1.8 dB/dB correspond to sidetone compensation

(equal autophonic level) and the same amount correspond to other cognitive effects

(Pelegrín-García, D., Fuentes-Mendizabal, O., Brunskog, J, and Jeong, C.H., 2011).

27   

4.3 Recommendations regarding room acoustic design

The voice support is a measure relating the room acoustic conditions of a classroom to the teachers’

use of their voice. This measure can therefore be used when designing a room. Here there are some initial recommendations for voice support:

 ST

V

< -17 dB: Very low. Teaching in this room is not to be recommended, unless an amplification system is used.

 -17 dB < ST

V

< -14 dB: Low. Amplification system is highly recommended.

 -14 dB < ST

V

< -9 dB: Good. Recommended values of voice support which can deliver optimum acoustical conditions.

 -9 dB < ST

V

< -6 dB: High. Only advisable in very small classrooms

 ST

V

> -6 dB: Excessive. Should be avoided. The decrease in voice level due to the sidetone compensation is remarkable and produces sensation of discomfort and decreases the voice quality. Higher values of STV than -6 dB when using electroacoustic amplification may result in a risk of feedback.

The range “Good” corresponds to the measured ST

_V

values in about 75% of the classrooms of our study in Sweden (which are considered acoustically satisfactory).

Using the validated prediction model in Pelegrin-Garcia, D., Brunskog, J., Lyberg-Åhlander, V.,

Rydell, R., & Löfqvist, A. (2011), ‘Measurement and prediction of acoustic conditions for a talker

in school classrooms’, equation (8), is it possible to relate these recommendations to the volume and

reverberation time, assuming a typical class room. This is done in Fig. 20. Assuming a typical

classroom to have a volume of 150 m

³

, we can say that the reverberation time should not be lower

28   

 

Figure 20: Voice support versus room volume for a room of proportions 28:16:10 according to the predictions of the model in Eq. (8), for different values of reverberation time.

5 Conclusions 

The following conclusions can be drawn from the project:

 The room acoustic conditions themselves have an effect on voice production. This is most obvious when the talker is aware of the acoustic environment, as in the following cases: the teacher has either week voice or voice problems, or the acoustic environment is unusual (e.g. anechoic condition). In addition, high background noise levels induce an increase in vocal effort.

 New acoustic measures, namely the voice support and the room gain, are well correlated with the changes in voice level among different rooms.

 The visually perceived distance between teacher and student accounts to a great extent for changes in vocal effort.

 Voice problems in teachers arise from the interplay of the individual and the environment.

Teachers with voice problems are more affected by factors in the work environment than their voice healthy colleagues. The differences between a group of teachers with self-assessed voice problems and their voice healthy colleagues were most clearly shown during field-measurements of the voice during a typical school day, while the findings from the clinical examinations of larynx and voice did not differ between the groups.

 The results from the prevalence study show that 13% of the teachers suffer from voice

problems frequently or always. Most teachers however, reported occurrence of symptoms of

vocal disturbances. Voice-related absence from work was common in both teachers with and

without voice problems.

29   

 The possibility for voice rest during the school day and also during teaching sessions is crucial for teachers with voice problems. The results suggest that teachers with voice problems have a higher vocal load during teaching and that this group has fewer opportunities for vocal rest and recovery during the school-day.

 When investigating or diagnosing voice dysfunction, the individual’s self assessment of the problems needs to be included. No correlation was found between subjective assessment of voice problems and deviations of laryngeal morphology or voice quality.

6 Publications and diffusion of knowledge from the project

Apart from the publications discussed so far, included in the appendix of this report, several other publications and presentations of the project have been made. There has also been spread of knowledge to the public in form of interviews and articles in newspapers and popular science magazines.

Conferences. The project has been presented at several international conferences in voice, acoustics or related areas:

 The pre-study where presented at the International Conference Acoustics, 2008 in Paris (Brunskog, J., Gade, A. C., Payá-Ballester, G., Reig-Calbo, L. 2008)

 The First Nordic Conference of Voice Ergonomics and Treatment 24-25/3 2009 (Pelegrin-Garcia, D. & Brunskog, J., 2009a; Lyberg-Åhlander, V., Rydell, R.; & Löfqvist, A, 2009)

 Inter-Noise 2009, Ottawa, Canada (Pelegrín-García, D., Brunskog, J. 2009b)

 EAA Euroregio 2010, Ljubljana, Slovenia (Pelegrín-García, D., Brunskog, J., 2010)

 Inter-Noise 2010, Lisbon, Portugal (Pelegrín-García, D., Fuentes-Mendizábal, O., Brunskog, J. and Jeong, C.-H., 2010; Bottalico, P., Pelegrín-Garcia, D., Astolfi, A., Brunskog, J. 2010)

 International Occupational Hygien Association (IOHA 2010), 8th International Scientific Confernace, Rome, Italy (Brunskog, J., Pelegrín-García, D., 2010) – an invited keynote speech at a workshop

 The 2nd Pan-American/Iberian Meeting on Acoustics and 160th Meeting of the Acoustical Society of America, Cancun, Mexico, 2010 (Pelegrín-García, D., Lyberg-Åhlander, V., Rydell, R., Löfqvist, A., and Brunskog, J., 2010)

The project has been presented at Afa’s noise conference in 2008, 2009 and 2010, at a meeting of the Noise Network (‘Människan och bullret’) in 2008 and again in 2010, and at the Voice Association's Conference April 2009. The prevalence study were presented at Voice Association's conference 24-25/4 2009, the Hearing Association's days 18/10. The Sound Environmental Center in Lund had a symposium day focusing on the project in September 2009, Speech comfort, acoustics and learning, with oral presentations by J Brunskog, V. Lyberg-Åhlander and D.

Pelegrin-Garcia. V, together with some invited speakers. Lyberg-Åhlander presented the project at

30   

Popular science and branch magazines. An early description of the project where published in the annual acoustic edition in branch magazine for the building industry Bygg & Teknik in Mars 2008 (Brunskog 2008). The final outcome of the project where presented in the same magazine in Mars 2011 (Brunskog, J., Pelegrín-García, D., Lyberg-Åhlander, V., Rydell, R., Löfqvist, A. 2011).

Radio and newspapers. A number of interviews have resulted in articles and radio spots as follows:

Vetenskapsradion, SR (11/12 2009); Skolvärden, Lärarnas riksförbund (2009); DIKforum

²

, DIKförbundet (2009); Röstläget, the magazine of the Voice Association (2009); Skolledaren, the magazine of the principal’s association (2010); Läkartidningen (2010); Speech Therapy

Association's magazine (2010); Forskning och Framsteg

³

(nr.2 2010); Skånska Dagbladet (27/3 2010); Lunds universitet meddelar (LUM) (2010); Östgöta Korrespondenten

⁴

(2010); and the information magazine of Ecophon Ecophon Acoustic Bulletin

⁵

(2010).

More activities. Viveka Lyberg-Åhlander has been asked by some schools to come and talk about what can be done to solve the teachers voice problems (among other, Lars-Erik Larsson High School in Lund). The teacher education in Kristianstad have invited Viveka Lyberg-Åhlander to talk about voice care in teacher's work, and she has been in contact with Ann-Marie Körling

⁶

, who is a teacher, lobbyist and very often referred person in teaching circles. The acoustic absorber company Ecophon (Jonas Christensson) want to involve us in training architecture students. Malmö Academy of Music would like that Viveka Lyberg-Åhlander talk to their music student teachers. J.

Brunskog and D. Pelegrin-Garcia have discussed the project with influential acousticians in

Denmark such as Dan Hoffmayer, DELTA (being deeply involved in regulations of, e.g.,

classroom), and Claus Møller Petersen, Grontmij|Carl Bro (the head of the Danish Acoustical

Society), etc. The reference group of the project has also been used as a channel of informing about

the project.

In document Speakers Comfort and voice disorders in classrooms Brunskog, Jonas; Lyberg Åhlander, Viveka; Löfqvist, Anders; Garcia, David Pelegrin; Rydell, Roland (Page 30-34)