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Combined and cross-modal effects of acoustics and air quality in classrooms
No full textDurante il Covid-19, sono stati adottati provvedimenti per prevenire la trasmissione in scuole e università. Una soluzione è stata di aumentare i ricambi d’aria mediante ventilazione meccanica o naturale. Questo ha migliorato la qualità dell’aria, il benessere e le capacità cognitive e di apprendimento. Tuttavia, ha anche aumentato l’esposizione degli studenti ai rumori, che potrebbero influenzare le stesse capacità cognitive. Nonostante i possibili effetti congiunti di acustica e qualità dell’aria sugli studenti, pochi studi hanno esaminato il loro impatto combinato.
Questa tesi studia come la qualità dell’aria e i suoni della ventilazione, sia meccanica che naturale, influenzino congiuntamente la abilità cognitive e la percezione sonora. Sono stati condotti tre esperimenti con studenti di diversa età. Il primo esperimento ha analizzato gli effetti di quattro suoni: ventilazione meccanica, canto degli uccelli, bambini che giocano e traffico in aula su 229 studenti (11-14 anni). I suoni sono stati riprodotti in cuffia a 47 dBA, e confrontati con una condizione di quiete. Sono state misurate la comprensione del testo, le abilità di calcolo e il soundscape. I risultati non hanno mostrato effetti significativi sulla comprensione del testo. Tuttavia, i tempi di risposta nei calcoli sono migliorati con i rumori antropici e peggiorati con la ventilazione meccanica. I rumori antropici sono stati giudicati caotici, la ventilazione monotona, mentre il canto degli uccelli è stato generalmente considerato piacevole.
Nel secondo esperimento, 193 studenti del primo studio sono stati esposti in laboratorio a cinque condizioni acustiche (silenzio, ventilazione meccanica a 47 e 52 dBA, canto degli uccelli, bambini che giocano) con due livelli di qualità dell’aria: buona (800 ppm CO2) e scarsa (2000 ppm CO2). I partecipanti hanno svolto test matematici e valutazioni sul soundscape. Non sono stati riscontrati effetti cognitivi diretti della qualità dell’aria. I rumori della ventilazione hanno prodotto i tempi di risposta più rapidi, mentre il rumore del parco giochi i più lenti. Le valutazioni del paesaggio sonoro sono rimaste simili al primo esperimento, ma livelli elevati di CO2 hanno peggiorato i giudizi sulla ventilazione meccanica.
Il terzo esperimento, condotto su studenti universitari (20-26 anni), ha esaminato gli effetti combinati di due livelli di CO2 (800 e 3000 ppm) e quattro condizioni sonore (silenzio, brusio di voci, ventilazione meccanica e canto degli uccelli) sulle abilità di calcolo e sull’effetto cross-modale della CO2 nelle valutazioni acustiche. Si è inoltre indagato se le risposte affettive degli adulti differissero da quelle dei bambini. I risultati hanno mostrato che l’aumento di CO2 rallenta le risposte. Sono emerse differenze significative nei tempi di risposta tra le condizioni sonore sotto alta CO2, con il rumore antropico che ha prodotto le risposte più rapide. Le valutazioni del paesaggio sonoro, invece, non hanno mostrato interazioni significative con la qualità dell’aria, confermando i trend precedenti.
In conclusione, sono stati identificati effetti cross-modali sulle valutazioni acustiche ed effetti combinati sulle capacità cognitive. L’effetto della CO2 sul soundscape è stato minimo e indipendente dall’età, con i fattori acustici sempre predominanti. Dal punto di vista cognitivo, solo le abilità di calcolo sono risultate influenzate dalle condizioni ambientali. Si ipotizza che questi fattori abbiano alterato i livelli di attivazione degli studenti durante i test, portandoli al livello ottimale o superandolo. L’età non ha avuto impatto, poiché le tendenze nei risultati cognitivi sono rimaste simili tra il primo e il terzo esperimento. Le differenze osservate, inclusa la presenza o assenza di effetti della CO2, sono probabilmente dovute alle caratteristiche individuali degli studenti, che possono influenzare i loro livelli basali di attivazione.During the Covid-19 pandemic, efforts were made to prevent virus transmission in schools and universities. One solution was to increase air exchanges by acting on mechanical or natural ventilation. This approach improved air quality, enhanced well-being, and potentially positively affected learning and cognitive abilities. However, it also increased students’ exposure to noises and sounds, which in turn may affect learning and cognitive abilities. Despite the overlapping effects of acoustics and air quality on students, few studies have explored their combined effects.
This dissertation aims to assess how air quality and ventilation sounds, either from mechanical or natural air flows, jointly influence cognitive performance and environmental assessments. The work is pursued by means of three dedicated experiments with panels of students of different ages. The first experiment evaluated the effects of four different sounds: mechanical ventilation, birdsong, children playing, and traffic noise. A total of 229 students (11-14 years old) were exposed in their classrooms to the aforementioned sounds, played at 47 dBA through headphones, and compared to a quiet control condition. Their reading comprehension, calculation skills, and soundscape assessments were measured. The results showed no significant effects of any sound condition on reading comprehension. However, response times on calculation improved with anthropic noise and worsened with mechanical ventilation. As concerns soundscape assessments, anthropic noise was rated as chaotic, mechanical ventilation as monotone, while birdsong was generally considered as pleasant.
In the second experiment, 193 students from the first experiment were exposed to five acoustic conditions (quiet, mechanical ventilation 47 and 52 dBA, birdsong, children playing), in a laboratory setting under two air quality levels: good (800 ppm CO2) and poor (2000 ppm CO2). Participants completed mathematical tasks and soundscape assessments. No direct cognitive effects of air quality were found. Mechanical ventilation noises led to the fastest response times, while playground noise produced the slowest. Soundscape rankings remained similar to Experiment 1, but high CO2 levels worsened evaluations of mechanical ventilation noise.
The third experiment with university students (20-26 years old) investigated the combined effects of two CO2 levels (800 and 3000 ppm) and four sound conditions (quiet, babble noise, mechanical ventilation, and birdsong) on calculation skills and the cross-modal impact of CO2 on soundscape assessments. The experiment also aimed to observe whether the affective responses of adults were different from those of children. The results showed that students slowed down as CO2 concentration increased. Significant differences in response times between sound conditions were observed under high CO2, with anthropic noise resulting in the fastest responses. Soundscape assessments, however, showed no significant interaction between sounds and air quality and the soundscape rating is the same of the previous experiments.
In conclusion, cross-modal effects on soundscape evaluations and combined effects on cognitive abilities were identified. For soundscape evaluations the impact of CO2 was minimal, and results were age-independent, with acoustic factors consistently dominating across all experiments.
On the cognitive side, only calculation skills were influenced by environmental conditions. It was hypothesized that the common effect of these factors across experiments was to alter students' arousal levels while undertaking the tasks; they reached or exceeded the arousal level required for optimal performance. Age had no impact, as similar trends in cognitive abilities were observed across experiments 1 and 3. The primary cause of differences, including the presence or absence of CO2 effects, is likely due to students’ personal traits, which in turn may influence baseline arousal levels
Soundscape and indoor air quality in naturally ventilated educational environments: a multi-domain study
No full textIn this study, indoor air quality (IAQ) and acoustics were jointly analysed to determine their i) combined effect on students' performance in a math task, and ii) cross-modal effect on soundscape perception. 192 students (12 to 14 years) took part in a laboratory experiment. Students were separated into two classroom-like chambers with different IAQ conditions: a CO2 concentration of 800 and 2000 ppm, respectively. The participants were asked to solve calculations and answer a soundscape questionnaire in three listening conditions: quiet, a natural scenario with birdsongs, and one scenario with children's playground activity sounds. In the latter two conditions, the sounds were played back through headphones at a level of 47 dBA. Results show that students had faster response times in the math task in quiet compared to the listening condition with children's activity sounds, while maintaining a similar task accuracy. No effect of the IAQ conditions and natural sounds was found on the task performance. No cross-modal effect of CO2 concentration on soundscape perception was detected. Regarding soundscape assessments, playground activity was rated as the most annoying listening condition, while listening to birdsongs was the most pleasant one, despite its noise level exceeding the quiet condition
Indoor soundscape in primary school classrooms
No full textSoundscape research on indoor environments is emerging as a topic to be addressed for the design of supportive, healthier, and more comfortable spaces. Only a few studies so far addressed the context of educational buildings, mainly focusing on high schools and universities. This pilot study uses questionnaires based on pictorial scales to investigate the indoor soundscape of classrooms for primary school children (n = 130; 8-10 years old). Perceived loudness and the affective dimensions of pleasantness and arousal were explored. Besides the actual soundscape, the children's ideal soundscape was investigated as well. The results of the study indicate that the most frequent sounds in classrooms are generated by the students themselves (voices, movements) followed by the traffic. The urban context of the school modulates the children's perception when windows are open to ensure natural ventilation. Pleasantness is associated with students' age, perceived loudness, and frequency of children's voices in nearby classrooms. The frequency of hearing indoor sounds (children's voices) and sirens affects students' arousal. Our results indicate that children at school are mostly exposed to unpleasant sounds, whereas their preferred ones are music and nature-related ones. The findings have implications for the design of positive and inclusive learning environments
Effects of type of early reflection, clarity of speech, reverberation and diffuse noise on the spatial perception of a speech source and its intelligibility
No full textChanging the balance between the early and late reflections in the impulse response affects the clarity of speech, and also the spatial perception of the sound source is affected when the direction of the early reflections is manipulated. While the effect of noise on early reflections has long been investigated in speech intelligibility studies, it is unclear whether and how the spatial characteristics of the source are altered by noise, and whether this would influence speech intelligibility in any way. The aim of the present work was to analyze the spatial perception of a speech source in noise and its relationship, if any, with speech intelligibility. Impulse responses with specular or scattered early reflections and two different reverberant tails were used to create sound fields with controlled clarity and reverberation. It emerged that noise affects spatial cues compared to the reverberation-only (quiet) condition; ratings are consequently changed, and most percepts are distorted. Speech intelligibility is also sensitive to changes in acoustic variables and the type of reflection, but the direct association between spatial percepts and speech intelligibility is weak
Effects of a single reflection from a diffusive surface on speech reception
No full textA large number of studies have been conducted on the
effect of specular reflections on speech reception, but
surprisingly little is available on the effect of diffuse
ones. This study focuses on the basic conceptual case of a
head-related impulse response (HRIR) with a single early
reflection, either specular or diffuse, besides the direct
sound. HRIRs were measured for several geometries in
an anechoic room. Sound fields were auralized and two
speech in noise experiments were presented to forty
normal hearing participants, using an uncorrelated
speech-like spectrum stationary noise as masker at a fixed
signal-to-noise ratio of -6 dB. The experiments were
designed to investigate the interaction between the quality
of reflection (specular vs diffuse) and (i) its temporal
delay from the direct sound, (ii) its azimuth
Listening effort for sentence comprehension in noisy classrooms: the mediating role of linguistic factors, inhibitory control, and noise sensitivity
No full textChildren learn in classrooms in the presence of background noise, mostly produced by the children themselves. Even when the acoustic conditions are favorable (i.e., low noise levels), differences in individual performance and listening effort in complex academic tasks are observed. Personal characteristics such as linguistic and cognitive skills and sensitivity to noise have been reported as factors supporting students’ performance. Moreover, the Framework for Understanding Effortful Listening (FUEL) postulates the additional, individual dimension of children’s motivation should be considered when evaluating listening effort, besides task cognitive demands.
This study aims to explore the interplay of the above-mentioned individual factors for primary school children (N=120, grades 3 to 5) doing a sentence comprehension task in two-talkers background noise. Data on both accuracy and response time, as well as self-ratings of effort and motivation, were acquired. In addition, inhibitory control, linguistic competencies, and self-ratings of noise sensitivity were measured in quiet. Results first highlight the interplay of acoustic conditions and linguistic competencies in shaping the child’s motivation in performing the task, and then show how the children’s inhibitory control and noise sensitivity mediate behavioral and subjective effort. Thus, individual factors shall be taken into consideration when evaluating the effect of classroom acoustics on performance in academic tasks
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Be Quiet! Effects of Competing Speakers and Individual Characteristics on Listening Comprehension for Primary School Students
Full text linkStudents learn in noisy classrooms, where the main sources of noise are their own voices. In this sound environment, students are not equally at risk from background noise interference during lessons, due to the moderation effect of the individual characteristics on the listening conditions. This study investigates the effect of the number of competing speakers on listening comprehension and whether this is modulated by selective attention skills, working memory, and noise sensitivity. Seventy-one primary school students aged 10 to 13 years completed a sentence comprehension task in three listening conditions: quiet, two competing speakers, and four competing speakers. Outcome measures were accuracy, listening effort (response times and self-reported), motivation, and confidence in completing the task. Individual characteristics were assessed in quiet. Results showed that the number of competing speakers has no direct effects on the task, whilst the individual characteristics were found to moderate the effect of the listening conditions. Selective attention moderated the effects on accuracy and response times, working memory on motivation, and noise sensitivity on both perceived effort and confidence. Students with low cognitive abilities and high noise sensitivity were found to be particularly at risk in the condition with two competing speakers
Individual characteristics moderate listening effort in noisy classrooms
Full text linkComprehending the teacher’s message when other students are chatting is challenging. Even though the sound environment is the same for a whole class, differences in individual performance can be observed, which might depend on a variety of personal factors and their specific interaction with the listening condition. This study was designed to explore the role of individual characteristics (reading comprehension, inhibitory control, noise sensitivity) when primary school children perform a listening comprehension task in the presence of a two-talker masker. The results indicated that this type of noise impairs children’s accuracy, effort, and motivation during the task. Its specific impact depended on the level and was modulated by the child’s characteristics. In particular, reading comprehension was found to support task accuracy, whereas inhibitory control moderated the effect of listening condition on the two measures of listening effort included in the study (response time and self-ratings), even though with a different pattern of association. A moderation effect of noise sensitivity on perceived listening effort was also observed. Understanding the relationship between individual characteristics and classroom sound environment has practical implications for the acoustic design of spaces promoting students’ well-being, and supporting their learning performance
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