Pentatonic sequences and monaural beats to facilitate relaxation: an EEG study.

Introduction: In two studies we investigated if specific acoustic stimulations could be more effective to induce a relaxation response in comparison to silence. Acoustic stimulations included monaural beats and musical sequences based on a pentatonic scale. Methods: In the first study, 47 participants evaluated monaural beats and pentatonic sequences presented through loudspeakers and varying along three frequencies (0.2, 2, 4 Hz). In the second study, 31 participants relaxed with their eyes closed for 10 min during a passive listening of monaural beats and a pentatonic sequence presented through loudspeakers. A silence condition was introduced as control. All auditory stimuli were designed with a temporal modulation of 0.2 Hz. Concomitant EEG was recorded with a 64-channel system and spectral analysis was performed on delta, theta, alpha, beta, and gamma oscillations to test if each of the three auditory stimulations had a significant effect on EEG spectral power in comparison to silence. Results: In the first study, pentatonic sequences were evaluated as more pleasant and more relaxing than monaural beats. Pleasantness and relaxation were inversely related to frequency. Visual imagery and emotion induction had higher frequency and were rated with a more positive valence in pentatonic sequences than in monaural beats. In the second study monaural beats in comparison to silence strongly decreased beta and gamma oscillations in the first three minutes and strongly increased theta oscillations in the last three minutes. Pentatonic sequences increased delta, theta, and alpha oscillations in the last three minutes while decreasing beta, and gamma oscillations for the whole auditory stimulation. Discussion: The results show that auditory signals with a very low temporal modulation (0.2 Hz) could be more effective than silence in inducing a relaxation response. Although 0.2 Hz monaural beats were effective in inducing a relaxation response, they tended to be perceived as unpleasant. Pentatonic sequences could be considered as a better alternative to promote relaxation by auditory stimulation.

Metacognition for hearing in noise: a comparison between younger and older adults.

Metacognition entails knowledge of one's own cognitive skills, perceived self-efficacy and locus of control when performing a task, and performance monitoring. Age-related changes in metacognition have been observed in metamemory, whereas their occurrence for hearing remained unknown. We tested 30 older and 30 younger adults with typical hearing, to assess if age reduces metacognition for hearing sentences in noise. Metacognitive monitoring for older and younger adults was overall comparable. In fact, the older group achieved better monitoring for words in the second part of the phrase. Additionally, only older adults showed a correlation between performance and perceived confidence. No age differentiation was found for locus of control, knowledge or self-efficacy. This suggests intact metacognitive skills for hearing in noise in older adults, alongside a somewhat paradoxical overconfidence in younger adults. These findings support exploiting metacognition for older adults dealing with noisy environments, since metacognition is central for implementing self-regulation strategies.

Indoor soundscape in primary school classroomsa).

Soundscape 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.

Individual characteristics moderate listening effort in noisy classrooms.

Comprehending 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.

Be Quiet! Effects of Competing Speakers and Individual Characteristics on Listening Comprehension for Primary School Students.

Students 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.

Effects of type of early reflection, clarity of speech, reverberation and diffuse noise on the spatial perception of a speech source and its intelligibility.

Changing 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.

A comparison of simultaneously-obtained measures of listening effort: pupil dilation, verbal response time and self-rating.

OBJECTIVE: The aim of this study was to assess to what extent simultaneously-obtained measures of listening effort (task-evoked pupil dilation, verbal response time [RT], and self-rating) could be sensitive to auditory and cognitive manipulations in a speech perception task. The study also aimed to explore the possible relationship between RT and pupil dilation. DESIGN: A within-group design was adopted. All participants were administered the Matrix Sentence Test in 12 conditions (signal-to-noise ratios [SNR] of -3, -6, -9 dB; attentional resources focussed vs divided; spatial priors present vs absent). STUDY SAMPLE: Twenty-four normal-hearing adults, 20-41 years old (M = 23.5), were recruited in the study. RESULTS: A significant effect of the SNR was found for all measures. However, pupil dilation discriminated only partially between the SNRs. Neither of the cognitive manipulations were effective in modulating the measures. No relationship emerged between pupil dilation, RT and self-ratings. CONCLUSIONS: RT, pupil dilation, and self-ratings can be obtained simultaneously when administering speech perception tasks, even though some limitations remain related to the absence of a retention period after the listening phase. The sensitivity of the three measures to changes in the auditory environment differs. RTs and self-ratings proved most sensitive to changes in SNR.

A Slight Increase in Reverberation Time in the Classroom Affects Performance and Behavioral Listening Effort.

OBJECTIVES: The purpose of this study was to investigate the effect of a small change in reverberation time (from 0.57 to 0.69 s) in a classroom on children's performance and listening effort. Aiming for ecological listening conditions, the change in reverberation time was combined with the presence or absence of classroom noise. In three academic tasks, the study examined whether the effect of reverberation was modulated by the presence of noise and depended on the children's age. DESIGN: A total of 302 children (aged 11-13 years, grades 6-8) with normal hearing participated in the study. Three typical tasks of daily classroom activities (speech perception, sentence comprehension, and mental calculation) were administered to groups of children in two listening conditions (quiet and classroom noise). The experiment was conducted inside real classrooms, where reverberation time was controlled. The outcomes considered were task accuracy and response times (RTs), the latter taken as a behavioral proxy for listening effort. Participants were also assessed on reading comprehension and math fluency. To investigate the impact of noise and/or reverberation, these two scores were entered in the statistical model to control for individual child's general academic abilities. RESULTS: While the longer reverberation time did not significantly affect accuracy or RTs under the quiet condition, it had several effects when in combination with classroom noise, depending on the task measured. A significant drop in accuracy with a longer reverberation time emerged for the speech perception task, but only for the grade 6 children. The effect on accuracy of a longer reverberation time was nonsignificant for sentence comprehension (always at ceiling), and depended on the children's age in the mental calculation task. RTs were longer for moderate than for short reverberation times in the speech perception and sentence comprehension tasks, while there was no significant effect of the different reverberation times on RTs in the mental calculation task. CONCLUSIONS: The results indicate small, but statistically significant, effects of a small change in reverberation time on listening effort as well as accuracy for children aged 11 to 13 performing typical tasks of daily classroom activities. Thus, the results extend previous findings in adults to children as well. The findings also contribute to a better understanding of the practical implications and importance of optimal ranges of reverberation time in classrooms. A comparison with previous studies underscored the importance of early reflections as well as reverberation times in classrooms.

Effects of multiple early diffuse reflections on spatial percepts.

While the use of diffuse surfaces is becoming increasingly common in the acoustical design of performance venues and normal rooms, there is a paucity of data on the auditory perceptual effects that characterize those finishes compared to specular ones. For instance, it is not entirely clear whether and how the aural impression is affected when first reflections are swapped from specular to diffuse. In a recent work, after revising the background knowledge on physical and perceptual effects of scattering, Visentin et al. [(2020) J. Acoust. Soc. Am. 148(1), 122-140] started a systematic analysis of how diffuse reflections influence the auditory impression by considering the simplest possible case, that is, a direct sound and one lateral reflection. The present work is a step forward in the analysis, and pairs of lateral reflections without or with a ceiling reflection are considered. By means of detailed listening tests, it is shown how diffuse reflections modulate the perception of some spatial attributes. This knowledge adds to the criteria to be employed when including diffusing surfaces in the design of first reflections in rooms.

Effect of a single lateral diffuse reflection on spatial percepts and speech intelligibility.

This study examines the influence of an early lateral reflection on spatial perceptual attributes and speech reception. To this aim, a diffuse reflection is compared with a specular one. Although diffusive surfaces have widespread applications in room acoustics design, the knowledge of the perceptual and behavioral outcomes of these surfaces has yet to be fully developed. Two experiments were conducted to investigate how the reflection type, its temporal delay, and its azimuth affect spatial percepts (source distance, width, and focus) and speech intelligibility (SI) in diffuse stationary noise. The experimental setup included ecological elements: field measurements, a speaker-like source directivity, and real flat and diffusive surfaces. The results indicate that the presence of a single diffuse reflection reduces the perceived distance of a frontal speech source and makes it clearer. SI is higher with a diffuse reflection than with a specular one. Perceptual and behavioral outcomes both depend on the angle of reflection given the frequency- and angular-dependent properties of the diffusing surface and the directivity of the speech source. The results are interpreted with reference to loudness and binaural cues and to the precedence effect. Implications of the findings for acoustic design are also discussed.

Impact of Background Noise Fluctuation and Reverberation on Response Time in a Speech Reception Task.

Purpose This study examines the effects of reverberation and noise fluctuation on the response time (RT) to the auditory stimuli in a speech reception task. Method The speech reception task was presented to 76 young adults with normal hearing in 3 simulated listening conditions (1 anechoic, 2 reverberant). Speechlike stationary and fluctuating noise were used as maskers, in a wide range of signal-to-noise ratios. The speech-in-noise tests were presented in a closed-set format; data on speech intelligibility and RT (time elapsed from the offset of the auditory stimulus to the response selection) were collected. A slowing down in RTs was interpreted as an increase in listening effort. Results RTs slowed down in the more challenging signal-to-noise ratios, with increasing reverberation and for stationary compared to fluctuating noise, consistently with a fluctuating masking release scheme. When speech intelligibility was fixed, it was found that the estimated RTs were similar or faster for stationary compared to fluctuating noise, depending on the amount of reverberation. Conclusions The current findings add to the literature on listening effort for listeners with normal hearing by indicating that the addition of reverberation to fluctuating noise increases RT in a speech reception task. The results support the importance of integrating noise and reverberation to provide accurate predictors of real-world performance in clinical settings.

Noise, Age, and Gender Effects on Speech Intelligibility and Sentence Comprehension for 11- to 13-Year-Old Children in Real Classrooms.

The present study aimed to investigate the effects of type of noise, age, and gender on children's speech intelligibility (SI) and sentence comprehension (SC). The experiment was conducted with 171 children between 11 and 13 years old in ecologically-valid conditions (collective presentation in real, reverberating classrooms). Two standardized tests were used to assess SI and SC. The two tasks were presented in three listening conditions: quiet; traffic noise; and classroom noise (non-intelligible noise with the same spectrum and temporal envelope of speech, plus typical classroom sound events). Both task performance accuracy and listening effort were considered in the analyses, the latter tracked by recording the response time (RT) using a single-task paradigm. Classroom noise was found to have the worst effect on both tasks (worsening task performance accuracy and slowing RTs), due to its spectro-temporal characteristics. A developmental effect was seen in the range of ages (11-13 years), which depended on the task and listening condition. Gender effects were also seen in both tasks, girls being more accurate and quicker to respond in most listening conditions. A significant interaction emerged between type of noise, age and task, indicating that classroom noise had a greater impact on RTs for SI than for SC. Overall, these results indicate that, for 11- to 13-year-old children, performance in SI and SC tasks is influenced by aspects relating to both the sound environment and the listener (age, gender). The presence of significant interactions between these factors and the type of task suggests that the acoustic conditions that guarantee optimal SI might not be equally adequate for SC. Our findings have implications for the development of standard requirements for the acoustic design of classrooms.

Investigating Listening Effort in Classrooms for 5- to 7-Year-Old Children.

Purpose This study aims to investigate the listening effort made by young children in real classrooms during a prolonged speech reception task in the presence of background noise. Method The experiment was proposed to 117 typically developing kindergarten and primary school pupils, aged 5-7 years old. An ecological experimental approach was followed, and speech-in-noise tests were presented in the classrooms to groups made up of the whole class. The speech material of the Word Intelligibility by Picture Identification Test in the Italian language ( Arslan, Genovese, Orzan, & Turrini, 1997 ) was presented in 2 listening conditions (quiet classroom [no noise added] and working classroom [with stationary noise]) and was repeated twice during the experiment. Data on the number of correctly recognized words and the single-task response time (RT) were collected; the quantity of the latter was considered informative on listening effort. Results It was found that when background noise was present, the pupils' performance decreased, and greater RTs were required compared to the "quiet classroom" condition. When the RTs were analyzed over the course of the experiment, there were no changes in the quiet condition, whereas in the working classroom, a significant increase was found for the 6- and 7-year-old pupils. On the contrary, the youngest pupils (5-year-olds) showed a decrease in the RT results over the test repetitions. Conclusions The RT measured with a single-task paradigm was found to be a viable approach for investigating the listening effort in 6- to 7-year-old pupils. For this age range, the metric was sensitive to changes both in the listening conditions and within the same listening condition across the time of exposure. More research is needed to assess the feasibility of the experimental paradigm with the 5-year-old children.

A Matrixed Speech-in-Noise Test to Discriminate Favorable Listening Conditions by Means of Intelligibility and Response Time Results.

Purpose: The primary aim of this study was to develop and examine the potentials of a new speech-in-noise test in discriminating the favorable listening conditions targeted in the acoustical design of communication spaces. The test is based on the recognition and recall of disyllabic word sequences. A secondary aim was to compare the test with current speech-in-noise tests, assessing its benefits and limitations. Method: Young adults (19-40 years old), self-reporting normal hearing, were presented with the newly developed Words Sequence Test (WST; 16 participants, Experiment 1) and with a consonant confusion test and a sentence recognition test (Experiment 2, 36 participants randomly assigned to the 2 tests). Participants performing the WST were presented with word sequences of different lengths (from 2 up to 6 words). Two listening conditions were selected: (a) no noise and no reverberation, and (b) reverberant, steady-state noise (Speech Transmission Index: 0.47). The tests were presented in a closed-set format; data on the number of words correctly recognized (speech intelligibility, IS) and the response times (RTs) were collected (onset RT, single words' RT). Results: It was found that a sequence composed of 4 disyllabic words ensured both the full recognition score in quiet conditions and a significant decrease in IS results when noise and reverberation degraded the speech signal. RTs increased with the worsening of the listening conditions and the number of words of the sequence. The greatest onset RT variation was found when using a sequence of 4 words. In the comparison with current speech-in-noise tests, it was found that the WST maximized the IS difference between the selected listening conditions as well as the RT increase. Conclusions: Overall, the results suggest that the new speech-in-noise test has good potentials in discriminating conditions with near-ceiling accuracy. As compared with current speech-in-noise tests, it appears that the WST with a 4-word sequence allows for a finer mapping of the acoustical design target conditions of public spaces through accuracy and onset RT data.

Listening efficiency during lessons under various types of noise.

Pupils inside primary school classrooms can be exposed to extraneous noise, impairing their performance in the speech reception process. The different noises show a peculiar impact, depending on their level, spectral content and temporal fine structure. In order to understand how the disturbance is built up over time, in this work a large data set was analyzed, detailing the changes of pupils' performance as the lesson progresses from the start to the end. Several types of noise are considered (traffic, tapping and activity noise) and the analysis concerns III to V graders of the Italian primary school (8 to 10 year old pupils). By using as indicators the intelligibility scores, the response time and their ratio, the so-called "listening efficiency," several findings are achieved. Pupils respond differently to each noise during the course of the lesson. In the better listening conditions, the performance in the speech reception worsens under traffic and babble noise whereas an opposite trend is found under tapping noise. On the contrary adaptation is observed in the worse listening conditions for the traffic noise alone. Moreover, indications are achieved that the age proficiency may affect differently babble noise compared to traffic and tapping noise.

An Italian matrix sentence test for the evaluation of speech intelligibility in noise.

OBJECTIVE: Development of an Italian matrix sentence test for the assessment of speech intelligibility in noise. DESIGN: The development of the test included the selection, recording, optimization with level adjustment, and evaluation of speech material. The training effect was assessed adaptively during the evaluation measurements with six lists of 20 sentences, using open- and closed-set response formats. Reference data were established for normal-hearing listeners with adaptive measurements. Equivalence of the test lists was investigated using the open-set response format at three signal-to-noise ratios (SNRs). STUDY SAMPLE: A total of 55 normal-hearing Italian mother-tongue listeners. RESULTS: The evaluation measurements at fixed SNRs resulted in a mean speech reception threshold (SRT) of -7.3 ± 0.2 dB SNR and slope of 13.3 ± 1.2 %/dB. The major training effect of 1.5 dB was observed for the first two consecutive measurements. Mean SRTs of -6.7 ± 0.7 dB SNR and -7.4 ± 0.7 dB SNR were found from the third to the sixth adaptive measurement for open- and closed-set test response formats, respectively. CONCLUSIONS: A good agreement has been found between the SRTs and slope and those of other matrix tests. Since sentences are difficult to memorize, the Italian matrix test is suitable for repeated measurements.

Experimental analysis of the relationship between reverberant acoustic intensity and energy density inside long rooms.

In this paper, the validity of the Fick's law of diffusion in room acoustics is experimentally investigated inside long rooms. The room-acoustics diffusion model relies on Fick's law stating a proportionality relationship between sound intensity and energy density gradient inside a room through a constant diffusion coefficient. This relationship is investigated in the stationary state for the particular case of long rooms with different amounts of boundary scattering. Measurements were performed inside a 1:16 scale model, using a p-u sound intensity probe (calibrated with digital filters) to collect concurrent data in terms of sound pressure and axial velocity components. Then for each receiver position, sound intensity and energy density gradient were derived. The results show that inside long rooms the diffusion coefficient is not a constant but increases with the distance from the source with a slope depending on the scattering coefficient of the walls. Numerical simulations of the enclosures were performed too by using a sound particle-tracing code; a substantial agreement with the experimental findings is observed. The results imply that for such long enclosures, the diffusion model should consider a space-varying diffusion coefficient to be more consistent with real phenomena.

An experimental evaluation of the impact of scattering on sound field diffusivity.

This work provides a systematic experimental evaluation of the impact of scattering on sound field diffusivity in a proportionate medium-small sized room. A scale model is set up in many ways by increasing the amount of scattering, and detailing measurements of the reverberation time in each case. With the aid of statistical tools, the role of scattering in the process of achieving a diffuse sound field from initially non-diffuse conditions is outlined and a set of reference scattering threshold values is derived. It is found that the same values ensure the validity of the Sabine formula when corrections are adopted in its application. Reverberation time is also predicted in non-diffuse conditions by the Nilsson approach, and its performance is systematically compared with measurements. The Nilsson method was a better predictor of reverberation time under non-diffuse conditions than classical reverberation time formulas. However, for diffuse sound fields, the same method tended to diverge from measured values. An application using more realistic room conditions is developed together with computer simulations. The results outline that there is limited benefit to using computer-aided design models instead of simple formulas to predict reverberation time for non-diffuse sound fields in proportionate medium-small sized rooms.

On the perception of speech in primary school classrooms: ranking of noise interference and of age influence.

It is well documented that the interference of noise in the classroom puts younger pupils at a disadvantage for speech perception tasks. Nevertheless, the dependence of this phenomenon on the type of noise, and the way it is realized for each class by a specific combination of intelligibility and effort have not been fully investigated. Following on a previous laboratory study on "listening efficiency," which stems from a combination of accuracy and latency measures, this work tackles the problems above to better understand the basic mechanisms governing the speech perception performance of pupils in noisy classrooms. Listening tests were conducted in real classrooms for a relevant number of students, and tests in quiet were also developed. The statistical analysis is based on stochastic ordering and is able to clarify the behavior of the classes and the different impacts of noises on performance. It is found that the joint babble and activity noise has the worst effect on performance whereas tapping and external traffic noises are less disruptive.

A numerical investigation of the Fick's law of diffusion in room acoustics.

In this paper the validity of the Fick's law of diffusion in room acoustics is investigated in the stationary state. The Fick's law, underlying the room-acoustics diffusion model, assumes a proportionality relationship between the local sound intensity and the energy density gradient, the proportionality constant being the so-called diffusion coefficient. This relationship, based on an analogy with the behavior of real particles in a scattering medium, is assessed by using a numerical tool simulating the actual dynamics of sound particles in a room. Two types of room geometries are considered: rooms with proportionate dimensions and long rooms. Concerning proportionate rooms the numerical analysis highlights the presence of weak variations of the reverberant energy density, generating an intensity vector pattern which is shown to be correctly described by the theoretical Fick's law and homogeneous diffusion. Conversely, inside long rooms, an estimate of the local value of the diffusion coefficient is carried out, showing that the reverberant sound field is well described by a spatially varying diffusion coefficient (non-homogeneous diffusion). The rate of increase of the estimated diffusion coefficient depends on the cross-sectional area of the room and on the boundaries absorption coefficient.