AFA projektrapport - Speakers Comfort
Projektet har löpt under fyra års tid och förutom projektledaren Jonas Brunskog även involverat Viveka Lyberg Åhlander, Anders Löfqvist, David Pelegrín-García och Roland Rydell. Projektet har omfattat två doktorandprojekt (Lyberg Åhlander samt Pelegrin-Garcia) varav Lyberg Åhlander nyligen disputerat på avhandlingen "Voice use in teaching environments - Speakers´ comfort, dep of Logopedics, Phoniatrics & Audiology, Clinical Sciences, Lund 2011.
I rapporten "'Speakers comfort and voice disorders in classrooms" beskrivs syftet sålunda: "The overall aim of the project has been to investigate the voice use of teachers in relation to the acoustic properties of the classroom, and to study whether speakers take into account auditory cues to regulate their voice levels, even in the absence of background noise".
Guidelines for Acoustic Design of Classrooms
Speaker-Oriented Classroom Acoustics Design Guidelines in the Context of Current Regulations in European Countries
Emanating from the Speakers Comfort-project a set of acoustic guidelines is now being proposed. With the aim of improving working conditions for teachers, David Pelegrin Garcia, Jonas Brunskog and Birgit Rasmussen presents guidelines for classroom acoustics design that meet simultaneously criteria of vocal comfort and speech intelligibility. Read the article here published in ACTA ACUSTICA UNITED WITH ACUSTICA Vol. 100 (2014) 1073 – 1089
Most European countries have regulatory requirements or guidelines for reverberation time in classrooms which have the goal of enhancing speech intelligibility and reducing noise levels in schools. At the same time, school teachers suffer frequently from voice problems due to high vocal load experienced at work. With the aim of improving working conditions for teachers, this article presents guidelines for classroom acoustics design that meet simultaneously criteria of vocal comfort and speech intelligibility, which may be of use in future discussions for updating regulatory requirements in classroom acoustics. Two room acoustic parameters are shown relevant for a speaker: the voice support, linked to vocal effort, and the decay time derived from an oral-binaural impulse response, linked to vocal comfort. Theoretical prediction models for room-averaged values of these parameters are combined with a model of speech intelligibility based on the useful-to-detrimental ratio and empirical models of signal-to-noise ratio in classrooms in order to derive classroom acoustic guidelines, taking into account physical volume restrictions linked to the number of students present in a classroom. The recommended values of reverberation time in fully occupied classrooms for flexible teaching methods are between 0.45 s and 0.6 s (between 0.6 and 0.7 s in an unoccupied but furnished condition) for classrooms with less than 40 students and volumes below 210 m3. When designing larger classrooms, a dedicated acoustic study taking into account considerations about geometry, material and speaker/audience placements should be made, which can help to increase the voice support and reduce the vocal effort.