Classroom acoustics for learning and well-being: in-field measurements, questionnaires and binaural speech intelligibility model

L'abstract è presente nell'allegato / the abstract is in the attachmen

THE EFFECT OF CLASSROOM ACOUSTICS ON STUDENTS’ LEARNING PROCESSES: SELECTION OF OBJECTIVE PARAMETERS AND PROVISION OF A MEASUREMENT PROTOCOL

Since the students’ learning process is affected by classroom acoustics, this work is based on a literature review aiming at identifying the acoustical parameters that have major influence on students’ academic performances. The review strategy involved three different approaches and resulted in more than 30 selected papers, of which only a few provided information on the effects of the acoustics of the environment on learning. The indexes that turned out to have the greater influence on students' performance were therefore considered on the evaluation of acoustical quality in elementary school classrooms through in-field measurements. Room acoustics and intelligibility indices in both occupied and unoccupied conditions of twenty-nine first-grade classrooms belonging to 13 school buildings in Turin that differ in location and typology, were gathered in the study. Then, the association between objective parameters was assessed with linear regression analysis and results of previous studies were confirmed. In addition to that, new important considerations useful for the creation of a simplified protocol that can be universally applied when performing acoustic measurements in classrooms emerged, so that comparisons across several environments can be performed

UN PROTOCOLLO PER LA CARATTERIZZAZIONE DELL’ACUSTICA DELLE AULE SCOLASTICHE DI PRIMA ELEMENTARE

Per promuovere una rapida ed efficace caratterizzazione, oltre che un’adeguata progettazione, dell'acustica dell’aula, questo studio fornisce un protocollo di misura essenziale, basato su un numero minimo di parametri e di posizioni. Le analisi condotte sui risultati delle misure acustiche di 29 aule suggeriscono l’utilizzo di parametri più convenienti, come la chiarezza nella posizione centrale dell'aula, rispetto al tempo di riverbero, che implica una procedura di misurazione più laboriosa

Intelligibilità del parlato e benefici spaziali in aule scolastiche con e senza trattamento di correzione acustica

La qualità acustica delle aule scolastiche influenza lo sviluppo del linguaggio, della comprensione e delle abilità cognitive degli studenti, soprattutto ai primi anni di scolarizzazione. In questo lavoro è stato applicato un modello di calcolo previsionale (Binaural Speech Intelligibility Model) per valutare l’effetto combinato di riverberazione e rumore proveniente da una sorgente co-locata e poi separata rispetto al ricevitore. Sono state considerate due aule di scuola primaria, una dotata di trattamento acustico e una no

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

Several studies have shown so far that poor acoustics inside classrooms negatively affects the teaching and learning processes, especially at the lowest grades of education. However, the extent to which noise exposure or excessive reverberation affect well-being of children at school in their early childhood is still unanswered, as well as their awareness of noise disturbance. This work is a pilot study to investigate to which extent classroom acoustics affects the perceived well-being and noise disturbance in first graders. About 330 pupils aged from 6 to 7 years participated in the study. They belonged to 20 classes of 10 primary schools located in Torino (Italy), where room acoustic measurements were performed and where noise level was monitored during classes. The school buildings and the classrooms were balanced between socioeconomic status and acoustic conditions. Trained experimenters administered questionnaires in each class, where pupils answered all together during the last month of the school year (May). Questions included the happiness scale, subscales assessing self-esteem, emotional health, relationship at home and with friends, enjoyment of school, intensity and noise disturbance due to different sound sources, and quality of voice. The findings of the study suggest that long reverberation times, which are associated with poor classroom acoustics as they generate higher noise levels and degraded speech intelligibility, bring pupils to a reduced perception of having fun and being happy with themselves. Furthermore, bad classroom acoustics is also related to an increased perception of noise intensity and disturbance, particularly in the case of traffic noise and noise from adjacent school environments. Finally, happy pupils reported a higher perception of noise disturbance under bad classroom acoustic conditions, whereas unhappy pupils only reported complaints in bad classroom acoustics with respect to the perception of pleasances with himself or herself and of fitting in at school. Being a mother tongue speaker is a characteristic of children that brings more chances of attending classes in good acoustics, of being less disturbed, and of having more well-being, and richer districts presented better acoustic conditions, in turn resulting in richer districts also revealing a greater perception of well-being

Optimal reverberation time in classrooms

Optimal reverberation time in classrooms when the noise source are nearby pupils is in the range of 0.3-0.9 s, with a preferred value around 0.7 s, according to Yang and Bradley (2009). Optimal reverberation time for the speaker in a classroom is around 0.75 s, according to several studies in which we monitored teachers’ voice in primary and secondary schools. This study involved 29 occupied primary-school classrooms in Italy where speech level (LS) and Sound Strength total (Gtot), early (G50) and late (Glate), have been measured at 1 m from the source and in other three positions along the main axis of the room. The background noise level during the measurements was less than 56 dB(A) and the reverberation time (RT) was between 0.5 s and 1.4 s. A cut-off value of RT was assumed equal to 0.8 s for subdividing the classrooms in two groups of similar size, with lower or equal and higher RT values, respectively. The slope per double distance of the speech level along the main axis, mLS, and of the Gtot, is -2 dB/dd for both the groups, while it is -3 dB/dd for G50. Glate shows a slope of -0.6 dB/dd and -0.9 dB/dd for the two groups, respectively. Optimal reverberation time range, between 0.6 s and 0.9 s, has been obtained in the case of Glate-G50 at the rear positions is set between 6 dB and 3 dB, respectively, with a central value of 0.7 s. This optimal value agrees with the previous literature findings

Elementary classroom acoustics: what really matters

This work answer the question on what are the optimal acoustic conditions for speech communication and learning in classroom. In order to do this, a simple protocol to carry out measurements to characterize classroom acoustics is provided and the thresholds of the main parameters to guarantee an adequate sound environment for educational facilities have been identified. In 29 first-grade classrooms, background noise level in silence and during group activities, reverberation time also in unoccupied conditions, speech clarity, ratio of useful to detrimental energy and speech signal were acquired along the main axis. Correlation analyses allowed for the selection of reverberation time or speech clarity in the central position as the essential parameters to evaluate the acoustical quality of classrooms, which were clustered either in bad or good acoustic group based on the cluster analysis. The thresholds for the reverberation time and speech clarity in the central position are 0.8 s and 2.6 dB, respectively. Further investigations were performed on the early, late and total components of the sound strength parameter

Sound propagation and strength in small classrooms

The study involved 29 occupied primary-school classrooms in Italy where speech level (LS) and Sound Strength total (Gtot), early (G50) and late (Glate), have been acquired at 1 m from the source and in other three positions along the main axis of the room. The background noise level during the measurements was less than 56 dB(A) and the reverberation time (RT) was between 0.5 s and 1.4 s. A cut-off value of RT was assumed equal to 0.8 s for subdividing the classrooms in two groups of similar size, with lower or equal and higher RT values, respectively. The slopes per double distance of the speech level along the axis, mLS, is −2 dB/dd for both the groups. The same slope per double distance is obtained for G50 of −2.7 dB/dd, while Glate shows a slope of −0.6 dB/dd and −0.9 dB/dd for the two groups, respectively. The slope per double distance of Gtot is −2.0 dB/dd as in the case of the speech level, mLs, as expected. Optimal reverberation time range, between 0.6 s and 0.9 s, in occupied conditions, has been obtained from the difference Glate-G50 at the rear positions between 6 and 3 dB, respectively

Spatial benefits on speech intelligibility in real classroom acoustics under energetic and informational masking noise

Challenging acoustic conditions, i.e. high noise and long reverberation time, negatively affect speech intelligibility. This is particularly true for school environments where learning is delivered, and students of every age develop their cognitive abilities. Research has primarily focused on the effect of reverberation and noise on speech intelligibility and on the spatial release from masking under laboratory conditions, whereas few studies considered these aspects ecologically. Also, the effect of noise on speech intelligibility was widely investigated considering its energetic rather than its informative content. This work deepens the extent to which the spatial release from masking is affected by reverberation and noise under real classroom acoustics, in order to help the design of learning environments to enhance speech intelligibility. Binaural room impulse responses were acquired at increasing speaker-to-listener distances, with noise sources at 0°, 120° and 180° from the listener’s head, in classrooms with reverberation times ranging from 0.4 s to 3.5 s, as to represent the typical conditions of Italian schools. Then, listening tests were performed: the impulse responses were convolved with speech and noise anechoic stimuli, and presented via headphone to a selected panel of normal hearing adults. Further analyses are now in progress; preliminary results reveal that speech intelligibility is worse under higher reverberation times and, averagely, under informational masking noise, as expected. As far as the spatial release from masking is concerned, when longer reverberation times are present in the room there is a tendency to have greater benefits under informational noise

Binaural Speech Intelligibility in a Real Elementary Classroom

Since the fundamental phases of the learning process take place in elementary classrooms, it is necessary to guarantee a proper acoustic environment for the listening activity to children immersed in them. In this framework, speech intelligibility is especially important. In order to better understand and objectively quantify the effect of background noise and reverberation on speech intelligibility various models have been developed. Here, a binaural speech intelligibility model (BSIM) is investigated for speech intelligibility predictions in a real classroom considering the effect of talker-to-listener distance and binaural unmasking due to the spatial separation of noise and speech source. BSIM predictions are compared to the well-established room acoustic measures as reverberation time (T30), clarity or definition. Objective acoustical measurements were carried out in one Italian primary school classroom before (T30= 1.43s±0.03 s) and after (T30= 0.45±0.02 s) the acoustical treatment. Speech reception thresholds (SRTs) corresponding to signal-to-noise ratio yielding 80% of speech intelligibility will be obtained through the BSIM simulations using the measured binaural room impulse responses (BRIRs). A focus on the effect of different speech and noise source spatial positions on the SRT values will aim to show the importance of a model able to deal with the binaural aspects of the auditory system. In particular, it will be observed how the position of the noise source influences speech intelligibility when the target speech source lies always in the same position