Increase in voice level and speaker comfort in lecture rooms

Abstract

Teachers often suffer from health problems related to their voice.These problems are related to their working environment, including the acoustics of the lecture rooms. However, there is a lack of studies linking the room acoustic parameters to the voice produced by the speaker.In this pilot study, the main goals are to investigate whether objectively measurable parameters of the rooms can be related to a increase of the voice sound power produced by speakers and to the speakers subjective judgments about the rooms. In six different rooms with different size, reverberation time and other physical attributes, the sound power level produced by six speakers was measured. Objective room acoustic parameters were measured in the same rooms, including reverberation time and room gain, and questionnaires were handed out to persons who had experience talking in the rooms. It is found that in different rooms significant changes in the sound power produced by the speaker can be found. It is also found that these changes mainly have to do with the size of the room and to the gain produced by the room. To describe this quality, a new room acoustic quantity called 'room gain' is proposed.

Measurement and prediction of voice support and room gain in school classrooms

“…The importance of the indirect component of one's own voice (also referred to as reflected sound), which is produced after the reflections of one's own voice at the room boundaries, is judged with two alternative measures introduced by Brunskog et al: 17 The room gain and the voice support. It is assumed that the airborne-direct sound reaching the ears has energy E D and that the reflected sound has energy E R .…”

“…16 In the presence of low background noise, speakers modify their voice power in different acoustic environments. 17,18 Other studies have also reported an effect of classroom acoustics on teachers' voices, 19,20 and there is a concern that excessive absorption may overdamp the voice of the speaker. 21 Therefore, the classroom acoustics conditions for speakers should also be taken into account during the design of schools.…”

“…The sound propagation of one's own voice can be direct from the mouth to the ears (which is equal in all environments under the same atmospheric conditions) or indirect through reflections at the room boundaries (which depends on the environment). Two magnitudes are proposed by Brunskog et al 17 to characterize the acoustic conditions for a speaker: The room gain and the voice support. The room gain is defined as the gain applied by the room boundaries to the voice of the speaker at his/her own ears (considering the airborne direct component as the "normal" voice level) and has been used in several studies.…”

Speaker-Oriented Classroom Acoustics Design Guidelines in the Context of Current Regulations in European Countries

“…Room acoustics was pointed out as one of the causes leading to voice problems. Moreover, a link was found between the voice power level used by a talker in a room and the amplication that a room produces on his voice at his own ears, in the presence of low noise levels [12,13]. This eect is related to the Lombard reex (increase of voice power level of a talker in the presence of noise) [14] and the café eect [15] (which is related to the inuence of the acoustic absorption in a room with several talkers on the voice power levels used by them; a decrease in absorption increases the energy of the reverberant eld and thus the sound pressure levels, which in turn lead the talkers to raise their voices due to the Lombard eect).…”

“…For this calculation, it is assumed that there are no obstacles closer than 1 m to the measurement device. If there would be, the direct sound should be derived from calibrated measurements in an anechoic chamber, as in [12]. ST V is minimum (ideally approaching −∞ dB) in free-eld, where there is no reected sound, and becomes higher the smaller the room and the higher the reverberation time.…”