The Chinese word identification and sentence intelligibility are evaluated by grades 3 and 5 students in the classrooms with different reverberation times (RTs) from three primary school under different signal-to-noise ratios (SNRs). The relationships between subjective word identification and sentence in- telligibility scores and speech transmission index (STI) are analyzed. The results show that both Chinese word identification and sentence intelligibility scores for grades 3 and 5 students in the classroom in- creased with the increase of SNR (and STI), increased with the increase of the age of students, and decreased with the increase of RT. To achieve a 99% sentence intelligibility score, the STIs required for grades 3, grade 5 students, and adults are 0.71, 0.61, and 0.51, respectively. The required objective acoustical index determined by a certain threshold of the word identification test might be underestimated for younger children (grade 3 students) in classroom but overestimated for adults. A method based on the sentence test is more useful for speech intelligibility evaluation in classrooms than that based on the word test for different age groups. Younger children need more favorable classroom acoustical environment with a higher STI than older children and adults to achieve the optimum speech communication in the classroom.
Simultaneous measurements of the indoor and outdoor particle mass (PM) and particle number (PN) concentrations as well as the air temperature, relative humidity (RH), and CO2 concentrations have been conducted in 6 occupied (L) and unoccupied (V) classrooms in 3 secondary schools in Lublin, Poland, in the heating (H) and summer (S) seasons. The schools were located in residential areas where the majority of private houses are heated by means of coal-burning stoves. The ratios of the average particle concentrations in occupied and unoccupied classrooms (L/V) were higher during the heating season measurements. The ratios of the average particle concentrations during the measurements in the heating and summer seasons (H/S) were higher in occupied classrooms. In both seasons the average PM and PN concentrations amounted to 239 μg/m3 and 7.4×103/cm3 in the occupied classrooms, and to 76 μg/m3 and 5.4×103/cm3 in the unoccupied classrooms, respectively. The particle exposures experienced by students were higher in the monitored classrooms than outdoors and were on average about 50% higher in the heating than in the summer season. A positive correlation between mass concentrations of coarse particles and indoor air temperature, RH and CO2 concentrations in both seasons was observed. The concentrations of fine particles were negatively correlated with the indoor air parameters in the heating season, and positively correlated in the summer season.