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.

Indoor working and living environments are increasingly exposed to low-frequency noise sources. The well-known relationship between noise conditions and effects on human health requires the development of a proper procedure to evaluate the stress due to acoustical factors. For this purpose, an experiment, based on Soft Metrology principles, was designed to measure the changes of cognitive and physiological parameters (response time and heart rate) on a sample of 25 male and female volunteers, aged 19–29 years, exposed to three types of noise in a hemi-anechoic room. Participants were involved in a cognitive task (Stroop effect) for 10 min in four different conditions: silence, stochastic broadband multi-tonal noise (BBN), stochastic low-frequency multi-tonal noise (LFN1), and low-frequency stationary noise with regular amplitude modulation (LFN2). All sounds were reproduced by two loudspeakers at equivalent sound pressure level of 93 dB. Results showed that in noise conditions, subjects reduced their response times. This is an evidence of growing stress, according to arousal theory. In particular, LFN1 and LFN2 produced cognitive stress comparable to stochastic broadband multi-tonal noise. Furthermore, subdividing the subjects in extroverts and introverts through the Eysenck Personality Questionnaire–Revised psychological test, it was shown that LFN1 and LFN2 produced higher stress effects than stochastic broadband multi-tonal noise on the cognitive performances and a physiological stress comparable to stochastic broadband multi-tonal noise in introverts, whereas no effects were observed in extroverts, as hypothesized by Eysenck. This result highlights the necessity in the future to consider the personality parameter as a key factor in the evaluation of the effects of noise on humans.

The need of tuning into speech in noisy and reverberant classrooms is a challenge for good speech communication and literacy development at school. Reading development can be compromised if children are exposed to inadequate acoustics, especially those with poor neural processing in speech discrimination. This work reports preliminary results on the influence of classroom acoustics on the reading speed of 94 Italian second-graders. Speech clarity (C50) was found to be significantly correlated with all the investigated reading tasks, while no significant correlations were found with reverberation time.

Acoustic metamaterials (AMMs) offer innovative solutions for physics and engineering problems, allowing lighter, multiphysics, and sustainable systems. They are usually studied analytically or numerically and then tested on prototypes. For this reason, additive manufacturing (AM) techniques are a popular way of quickly realising AMMs' innovative geometrical designs. However, AM parameters are often standardised without considering the specific issues of each AMM geometrical shape, leading to a possible mismatch between the analytical (or numerical) and experimental results. In this study, a simple AMM—a coiled-up resonator—has been produced with different AM technologies [fused deposition modeling (FDM), stereolithography (SLA), and selective laser melting and materials (polylactic acid, polyethylene terephthalate glycol, resin, flexible resin, and stainless steel). The sound absorption performance of these samples has been measured in two research labs in Italy and compared with the analytical and numerical calculations. This permitted the identification of the best combinations of AM technologies, their setup, and materials matching the expected results. The SLA/resin combination performed better overall; however, cheaper and more easily manageable samples made with FDM and polyethylene terephthalate glycol can achieve the same acoustic performance through the optimal AM printing setup. It is expected that this methodology could also be replicated for other AMMs.

Traceability of digital sensors is a metrological challenge, as well as a present priority, as stated within the emerging metrology requirements for the future in the Strategy 2017 to 2027 document of the Consultative Committee for Acoustics, Ultrasound, and Vibration of BIPM. From this perspective, in this paper, a calibration system for 3-axis digital MEMS accelerometers is described, in order to simultaneously evaluate the main and transverse sensitivities in the frequency domain (from 5 Hz up to 3 kHz) and in static conditions, together with a proper sensitivity parameter for digital outputs, thus providing the required metrological traceability. The procedure, based on the comparison to a reference transducer, involves a single-axis excitation of inclined planes. Experimental results are expressed in terms of exploitation and sensitivities matrices. Overall expanded uncertainties of the main terms are in the order of 2%, in dynamic conditions, and 1%–2% in static conditions. The feasibility of this system can be exploited for the development of manufacturers’ in-line control systems and for the investigation of large-scale calibration procedures.