Four-day-follow-up study on the voice monitoring of primary school teachers: Relationships with conversational task and classroom acoustics

Abstract

The present study has investigated the occupational voice use of 27 female primary school teachers over a four-day-follow-up. Sixty-one working-day voice samples were acquired with two contact sensor-based vocal analyzers in four schools with highly different classroom acoustics. The vocal parameters were compared with a conversational task that the teachers performed before each lesson and with the measured classroom acoustic parameters. The average equivalent sound pressure level at 1 m from the mouth, which refers to the teacher's vocal effort, and the voicing time percentage were 71.2 dB [standard error (SE) 1.0 dB] and 29%, respectively. The teachers' mean voice level and fundamental frequency were significantly higher in the occupational setting than in the conversational one, which is by 5.5 dB (SE 0.5 dB) and 50 Hz (SE 3 Hz), respectively. Higher voice levels were observed for higher background noise levels, at a rate of 0.53 dB/dB, and a tendency of the background noise to increase with increasing reverberation time was observed at a rate of 13 dB/s. An optimal reverberation time of 0.7 s was found to minimize the voice level, since teachers raised their voice at lower and higher reverberation times, the latter presumably due to higher background noise levels.

Influence of Classroom Acoustics on Noise Disturbance and Well-Being for First Graders

“…The parameters L N_sil , L N_gr , L S_REF , and mL S are positive related to the reverberation time, that is when T20 is higher they are higher, as expected, and negatively related to C50 and U50. A very tight connection is shown between central and mean values of the quantities C50 and U50, thus bringing to the practical conclusion that only one measurement in the center of the room can well describe the behavior of the whole classroom in terms of speech intelligibility, as already shown by Puglisi et al (2017). U50_ctr is also well related to C50_ctr, which suggests the use of only one quantity instead of two to represent speech intelligibility.…”

“…On the one side, with very high reverberation time, primary school teachers raise their voice in order to be understood by pupils (Bottalico and Astolfi, 2012;Puglisi et al, 2017). This is mainly due to the effect of amplification of indoor noise due to excessive sound reflection.…”

“…High noise levels can bring dysphonia or other vocal pathologies for teachers (Astolfi et al, 2012a;Bottalico et al, 2017a,b), which in turn can determine increased listening difficulties for children (Rudner et al, 2018). On the other side, thanks to voice monitoring performed with professional dosimeters (Carullo et al, 2013;Bottalico et al, 2018) and the uncertainty estimation of the vocal parameters Astolfi et al, 2018a), research has shown detrimental effects in speech production either in low reverberation or in high reverberation in the absence of noise, and optimal reverberation times for speaking have been proposed (Pelegrín-García et al, 2014;Calosso et al, 2017;Puglisi et al, 2017).…”

“…Frequency averages were calculated according to Din 18041 (2016) in the range 0.25-2 kHz for T20 and according to ISO 3382-1 (2009) in the range 0.5-1 kHz for C50. A range of optimal occupied T20 was set between 0.5 and 0.8 s, according to a number of recent studies (0.7 s in Yang and Bradley, 2009; 0.8 s in Bottalico and Astolfi, 2012; 0.5-0.6 s in Pelegrín-García et al, 2014; 0.7 s in Puglisi et al, 2017;and 0.8 s in Calosso et al, 2017), which concerned both speech and listening performance in typical primary and secondary school classrooms. Therefore, for the subsequent analyses, classes were split into GA and BA whether they were in or out of such optimal range, respectively.…”

“…As given in Bradley (1986), it is assumed that an optimal value of C50 for small classrooms with an optimal reverberation time of 0.8 s at middle frequencies should be greater than around 3 dB. T20 in unoccupied conditions, T20_e, where the subscript "e" is for empty, was measured with a wooden clapper, i.e., two wooden boards hinged together, according to the ISO 3382-2 (2008), as described in Puglisi et al (2017). The measurement method in the empty condition was different compared to the one in the occupied condition; however, the two procedures can be considered equivalent in the frequency range of interest as described in Puglisi et al (2018).…”