Pressure Levels Research Articles

A novel dataset of indoor environmental conditions in work-from-home settings

During the last week of March 2020, millions of workers around the world transitioned to working from home due to the COVID-19 pandemic. While much research has explored the behavioural and psychological aspects of work-from-home (WFH), few studies have provided data-driven evaluations of indoor environmental quality (IEQ). This paper presents findings from a summer 2022 field study of IEQ conditions in WFH settings, involving 95 participants in the North American Pacific Northwest. Sensors installed on participants' work desks continuously measured total volatile organic compounds (tVOC), particulate matter (PM2.5), carbon dioxide (CO2) air temperature, humidity, and sound pressure levels (SPLs). Participants also completed surveys on home and workspace characteristics, as well as their subjective assessments of IEQ, well-being, and productivity. The study found that mean indoor concentrations of tVOC, PM2.5, and CO2 were 262 ppb, 5 µg/m3, and 712 ppm, respectively. Indoor air temperature ranged between 14.7–32.3°C, with a mean of 22.8°C, while relative humidity and SPL averaged at 52.5% and 53.7 dBA. Statistically-significant associations were observed between IEQ variables and factors such as residence type, cooking habits, workspace type, and window availability. A future paper will assess the surveyed behavioural and psychological characteristics in greater detail.

Effects of sound on bluff body aerodynamic characteristics in separated and reattaching flows

The coupling effects between sound and flow on the aerodynamic characteristics of bluff bodies are commonly encountered in engineering practices, such as wind turbine blades and heat exchanger compressors. This study experimentally investigates the effects of sound over a broad range of frequencies (0–400 Hz) and sound pressure levels (80–105 dB) on the streamwise wind pressures on a flat plate in both smooth and turbulent flows. Spectral analysis and proper orthogonal decomposition (POD) are employed to explore the effects of sound on the aerodynamic forces acting on the flat plate. The results show that the effects of sound on wind pressure distributions and separation bubble behaviors over the flat plate depend on both sound frequency and sound pressure level. Furthermore, the findings highlight the role of acoustic resonance, which can increase the fluctuating wind pressure on the plate surface by over 400%. These effects can also be influenced by sound pressure levels. Additionally, the results demonstrate varying degrees and forms of attenuation of sound effects in turbulent flows, depending on the wind flow characteristics.

Noise reduction of an airfoil model covered by bio-inspired herringbone riblets

It is curious that whether the typical herringbone pattern of bird flight feathers plays a role in attenuating aeroacoustic noise. Being motivated by this, experiments are conducted to investigate noise reduction of the NACA0012 (National Advisory Committee for Aeronautics) airfoil-based model with one side surface covered by bio-inspired herringbone patterns of riblets. The herringbone-ribbed surface is defined by the divergent angle β (= 60°) of the riblets pattern, the spanwise wavelength λ (= 0.2c and 0.4c) of the pattern, and the riblet height h (= 0.6%c and 1.2%c), where c is the chord length of the airfoil. While far-field sound pressure fluctuations are measured via microphones in an anechoic wind tunnel, flow fields around the model are captured using particle image velocimetry (PIV) in a water tunnel. The effective angle of attack of the test models ranges from αeff = −11.1° to 11.1° and Reynolds number considered is from Re = 2.3 × 105 to 7.8 × 105. Compared with the baseline smooth models, the models with the riblet pattern on the pressure side are able to substantially suppress the tonal noise, associated with considerable reduction in the overall noise. The reduction in the overall sound pressure levels of the tonal noise and the overall noise are up to 21.3 dB and 20.5 dB, respectively, at αeff = −2.2° and Re = 3.6 × 105. The noise reduction is attributed to the transition of laminar to turbulent boundary layers over the herringbone-ribbed surface, particularly in the saddle location where the spanwise-repeated herringbone pattern converges. Behavior of shear layers separating from the trailing edge of the model is examined, corroborating the proposition that the acoustic feedback loop is impaired by the herringbone-ribbed surface.

Development of a novel light-sensitive PPG model using PPG scalograms and PPG-NET learning for non-invasive hypertension monitoring

Background and objectivePhotoplethysmography (PPG) signals provide a non-invasive method for monitoring cardiovascular health, including blood pressure levels, which are critical for the early detection and management of hypertension. This study leverages wavelet transformation and special purpose deep learning model, enhanced by signal processing and normalization, to classify blood pressure stages from PPG signals. The primary objective is to advance non-invasive hypertension monitoring, improving the accuracy and efficiency of these assessments. MethodsThe study employed continuous wavelet transform (CWT) to prepare PPG signals for analysis using a special purpose PPG-NET designed by applying advanced deep-learning models. PPG-NET was verified by applying several pre-trained models, including Inception, MobileNetV2, InceptionResNetV2, and others to the PPG data. Rigorously five-fold cross-validated models were conducted to obtain the models' performance to ensure robustness and repeatability of results. ResultsThe PPG-NET model demonstrated superior performance, achieving a perfect accuracy of 100 % in classifying the four stages of hypertension—normal, prehypertension, stage 1, and stage 2. The evaluation metrics reported include precision, sensitivity, and specificity, with the PPG-NET model achieving 100 % across all metrics. Other models showed varying levels of accuracy, with InceptionV3 also reaching 91.5 %, while some, like VGG-19, underperformed significantly. ConclusionsIntegrating CWT and PPG-NET offers a promising avenue for enhancing non-invasive blood pressure monitoring. The PPG-NET model, in particular, showed potential for clinical application due to its high accuracy and reliability. This study showed the effectiveness of combining advanced computational techniques with traditional PPG analysis, potentially leading to more personalized and accessible hypertension management strategies.

Failure monitoring and classification from acoustic emission tests on impact-damaged hydrogen composite pressure vessels

Composite overwrapped pressure vessels (COPV) for hydrogen will play an important role in emission free mobility and energy storage. The DELFIN project (2018 – 2022) was set up with the goal of developing improved COPVs that are lighter, cheaper and more durable. A key aspect of this project was to conduct full-scale impact tests with different gas pressure levels that were used to evaluate the vessels’ crash performance and to verify numerical impact simulations. These tests were followed by controlled pressure experiments until the burst pressure was reached. The procedure was monitored with acoustic emission testing (AT) and subsequent computer tomography (CT). The residual COPV stability and the AT results are compared to different scenarios regarding the impact energies and impact angles. The event localization from AT shows a clear correlation of the emitted energy with the damaged areas. We classify the recorded signals into groups that can be related to the failure mechanism and compare those to the pressure evolution before failure of the COPV. All tests indicate that large impact energies lead to a significant reduction of the burst pressure of COPVs, whereas a higher internal pressure can have a stabilizing effect that reduces the damaging effect.

Research on flow-induced radiated noise of twin-screw pumps based on the Lighthill acoustic analogue theory

Abstract To optimize the control of twin-screw pumps (TSP), it is essential to ensure performance while simultaneously preventing noise levels from exceeding specified limits. In order to investigate the flow characteristics and the mechanism of flow-induced radiated noise under various operating conditions, a coupled numerical simulation approach using Computational Fluid Dynamics (CFD) and Computational Acoustics (CA) was employed, and the findings were validated through experiments. The study reveals that the highest sound pressure levels of radiated noise occur near the rotor outlet surface, and the dynamic-static interference at the rotor-boundary interface is the primary cause of flow-induced noise in TSP. The flow-induced noise in TSP exhibits dipole characteristics, with the overall sound pressure level gradually increasing and then sharply rising with the increase in rotational speed (or flow rate). It stabilizes near the design operating point and continues to increase steadily with further increases in rotational speed (or flow rate). Modal testing using a dual-distributed measurement technique highlights significant interference effects between the rotor inlet and the dynamic rotor for the first two Blade Passing Frequencies (BPF) in TSP. The results of this study provide a theoretical foundation for the low-vibration and low-noise design and operation of TSP.

Aeroacoustic and aerodynamic measurements at the rotor plane in the interaction of a small rotor with wings.

Current research on tiltrotor noise predominantly concentrates on configurations with high disk loading and Reynolds numbers, leaving smaller aircraft setups underexplored. This study investigates aeroacoustic and aerodynamic trends resulting from rotor-wing interaction at low disk loading (<100 N/m2) and Reynolds number (Re < 100 000). The experimental setup comprises an anechoic chamber housing a two-blade rotor, flat and National Advisory Committee for Aeronautics 0012 airfoil wings, an ATI mini 40 load cell for aerodynamic data acquisition, and microphones positioned at the rotor height and installed on a rotation stage for acoustic data capture and directivity check. Investigated factors encompass rotor height, rotation direction, revolutions per minute (RPM), and wing curvature. Contrary to expectation, wing curvature does not visibly impact rotor performance. However, the deflected rotor wake in rotor-wing interaction markedly amplifies low-frequency broadband noise and the overall sound pressure level for the tested scenarios. The presence and strength of the deflected rotor wake tend to obscure the primary tonal noise and mitigate the effect of rotor RPM at smaller rotor spacings. This study provides valuable insights into mitigating noise resulting from rotor wake impingement on the wing in smaller aircraft configurations, contributing to the ongoing evolution of urban air mobility design considerations.

Main risk factors for the development of chronic non-communicable diseases among residents of the Altai Territory

Purpose of the study. analysis of the prevalence of the main risk factors for the development of chronic NCDs in the unorganized population of the Altai Territory aged 25–64 years.Materials and methods. The study involved 1,103 people aged 25–64 years, selected by random sampling from the population of the Altai Territory. The survey was conducted using a standard questionnaire. During the study, the blood pressure level, height, and weight of respondents were measured.Results. The study involved 1103 people, of whom 33.4 % were men (n = 368), women – 66.6 % (n = 735). Smoking was registered in 21.5 % (n = 234), among men – 45.7 % (n = 166), among women – 9.4 % (n = 68). IBP of salt was detected in 58.9 % (n = 650), among men – 63.6 % (n = 234), among women – 56.6 % (n = 416). Consumption of less than 5 servings of fruits and/or vegetables on average per day was noted in 55.7 % (n = 597), among men – 67.6 % (n = 244), among women – 49.6 % (n = 353). NFA occurs in 19.9% (n = 218), among men – 19.4 % (n = 71), women – 20.1 % (n = 47). Obesity occurs in 34.9 (n = 349), among men – 22.3 % (n = 73), women – 41% (n = 276). High blood pressure among all respondents was 50.3 %; in men this risk factor was lower than among women (45.4 % and 52.8 %, respectively).Conclusions. For the first time, the features of the main risk factors for the development of chronic non-diseases were studied in an unorganized sample of the region’s population aged 25–64. Residents of the region have a high incidence of salt IBP, NPOF and elevated blood pressure. The ESSE-RF study made it possible to identify gender and territorial characteristics of our region. Thus, the study demonstrated that both sexes have NPOF and salt IBP, but smoking was more common among men, and high blood pressure among women. This study is the starting point for epidemiological studies in the Altai region and can serve as a guide for further monitoring of the prevalence of risk factors and the effectiveness of preventive programs.

Finite element analysis and detection of melanoma cells under dual-cell photoacoustic interference conditions

In order to detect the presence of melanoma cells in two cells under the condition of cell photoacoustic wave interference, this paper conducted a finite element analysis of the photoacoustic wave interference field of two cells. First, the wavelength corresponding to the dominant frequency of the signal from a single red blood cell (mean diameter) was calculated. Then, the distance between two identical red blood cells (mean diameter) was set as a multiple of the wavelength to identify the optimal interference distance and the position of the enhanced zone detection point. Next, under the optimal distance, the signal curves of two cells as red blood cells and when melanoma cells exist in two cells were calculated in sequence. Finally, the frequency domain sound pressure level curve of the detection point under the two states was compared with the single-cell signal to obtain the Frechet distance. The results show that when both cells are red blood cells, the Frechet value is less than 48; when melanoma cells exist in both cells, the Frechet value is greater than 52. This study shows that the presence of melanoma cells in two cells can be determined by adjusting the distance between the cells, arranging the positions of the detection points, and employing the Frechet distance metric curve difference under the condition that the two-cell photoacoustic waves interfere with each other.

Relationship Between Age and Blood Pressure in Patients Postoperative Sectio Caesarea

Background: Cesarean section (C-section) is a surgical procedure for childbirth, involving an incision in the uterine wall through the abdomen, typically indicated for various medical reasons. Spinal anesthesia is commonly employed during C-sections, although it is associated with side effects such as fluctuations in blood pressure. The majority of C-section patients under spinal anesthesia are between 20 and 35 years of age, considered the optimal reproductive years for pregnancy and childbirth. Purpose: This study aims to evaluate the correlation between age and blood pressure in postoperative C-section patients under spinal anesthesia. Methods: A cross-sectional, observational-analytical study design was used, involving 81 purposively sampled respondents. Data were analyzed using Spearman's rank correlation to assess the relationship between age and blood pressure postoperatively. Findings: The majority of respondents (67.9%) were aged between 20 and 35 years. Postoperative blood pressure in the recovery room was predominantly within the normal range, with 71.6% of patients displaying normal blood pressure levels. A statistically significant correlation was found between age and blood pressure, with a p-value ≤ 0.05. Conclusion: Age is significantly associated with postoperative blood pressure in patients undergoing C-sections under spinal anesthesia. This finding highlights the importance of monitoring blood pressure in this population to ensure optimal recovery outcomes.

Revisiting the sound absorption mechanisms of a finite flexible perforated panel absorber using a numerical approach.

This study investigates the sound absorption mechanisms of a finite flexible perforated panel absorber. Different from existing work where the mechanisms were often investigated by comparing the sound absorption coefficient curves of different absorber configurations, a numerical approach, called virtual impedance tube (VIT) technique, is developed and used for the analysis. One advantage of this technique is the vast dataset generated can be used to investigate the sound absorption mechanisms from an energy standpoint. The developed VIT technique is first validated using the impedance tube test, where a proportion-integration-differentiation control algorithm is developed to maintain the incident sound at a desired sound pressure level. Then, the sound absorption mechanisms at three absorption peaks, i.e., hole-cavity controlled, panel-cavity controlled, and panel controlled, are investigated and the dominant energy dissipation mechanism at different sound pressure levels (SPLs) is revealed. Finally, an impedance model that takes account of the panel vibration and is applicable to various SPLs is proposed and validated.

Sonic restoration: acoustic stimulation enhances plant growth-promoting fungi activity.

Ecosystem restoration interventions often utilize visible elements to restore an ecosystem (e.g. replanting native plant communities and reintroducing lost species). However, using acoustic stimulation to help restore ecosystems and promote plant growth has received little attention. Our study aimed to assess the effect of acoustic stimulation on the growth rate and sporulation of the plant growth-promoting fungus Trichoderma harzianum Rifai, 1969. We played a monotone acoustic stimulus (80 dB sound pressure level (SPL) at a peak frequency of 8 kHz and a bandwidth at -10 dB from the peak of 6819 Hz-parameters determined via review and pilot research) over 5 days to T. harzianum to assess whether acoustic stimulation affected the growth rate and sporulation of this fungus (control samples received only ambient sound stimulation less than 30 dB). We show that the acoustic stimulation treatments resulted in increased fungal biomass and enhanced T. harzianum conidia (spore) activity compared to controls. These results indicate that acoustic stimulation influences plant growth-promoting fungal growth and potentially facilitates their functioning (e.g. stimulating sporulation). The mechanism responsible for this phenomenon may be fungal mechanoreceptor stimulation and/or potentially a piezoelectric effect; however, further research is required to confirm this hypothesis. Our novel study highlights the potential of acoustic stimulation to alter important fungal attributes, which could, with further development, be harnessed to aid ecosystem restoration and sustainable agriculture.

Exposure to aircraft noise exacerbates cardiovascular and oxidative damage in three mouse models of diabetes.

Epidemiology links noise to increased risk of metabolic diseases like diabetes and obesity. Translational studies in humans and experimental animals showed that noise causes reactive oxygen species (ROS)-mediated cardiovascular damage. The interaction between noise and diabetes, specifically potential additive adverse effects, remains to be determined. C57BL/6 mice were treated with streptozotocin (i.p. injections, 50 mg/kg/d for 5d) to induce type-1 diabetes, with S961 (subcutaneous osmotic minipumps, 0.57 mg/kg/d for 7d) or fed a high-fat diet (HFD, 20 weeks) to induce type-2 diabetes. Control and diabetic mice were exposed to aircraft noise to an average sound pressure level of 72 dB(A) for 4d. While body weight was unaffected, noise reduced insulin production in all diabetes models. The oral glucose tolerance test showed only an additive aggravation by noise in the HFD model. Noise increased blood pressure and aggravated diabetes-induced aortic, mesenteric, and cerebral arterioles endothelial dysfunction. ROS formation in cerebral arterioles, the aorta, the heart, and isolated mitochondria was consistently increased by noise in all models of diabetes. Mitochondrial respiration was impaired by diabetes and noise, however without additive effects. Noise increased ROS and caused inflammation in adipose tissue in the HFD model. RNA sequencing data and alteration of gene pathway clusters also supported additive damage by noise in the setting of diabetes. In all three models of diabetes, aircraft noise exacerbates oxidative stress, inflammation, and endothelial dysfunction in mice with pre-existing diabetes. Thus, noise may potentiate the already increased cardiovascular risk in diabetic patients.

Land and Atmospheric Drivers of the 2023 Flood in India

AbstractFloods in India are recurring natural disasters resulting from extreme precipitation during the summer monsoon season (June–September). The recent flood in North India in July 2023 caused substantial damage to lives, agriculture, and infrastructure. However, what led to the 2023 North India flood and the role of atmospheric and land drivers still need to be examined. Using in situ observations, satellite data, and ERA5 reanalysis combined with hydrological and hydrodynamical modeling, we examine the role of land and atmospheric drivers in flood occurrence and its impacts. Extreme precipitation in a large region during 7–10 July 2023 created favorable conditions for the flood in the hilly terrains and plains of north India. More than 300 mm of precipitation fell in just 4 days, which was eight times higher than the long‐term average (2001–2022). Anomalously high moisture transport over northern India was recorded on 7 July 2023, making atmospheric conditions favorable for intense landfall. Increased column water vapor and specific humidity at different pressure levels confirmed the continuous moisture presence before the extreme rainfall that caused floods in northern India from 7 to 12 July 2023. Atmospheric and land (high antecedent soil moisture) conditions contributed to a more than 200% rise in streamflow at several gauge stations. Satellite‐based flood extent shows a considerable flood inundation that caused damage in the Sutlej and Yamuna River basins. Our findings highlight the crucial role of the favorable land and atmospheric conditions that caused floods and flash floods in north India in July 2023.

Reflection function, reflectance, and area function measurements in ears of children and adults.

The main experiment concerned time-domain measurements of the acoustical reflection function (RF) of the human ear in adults and children (aged 5 to 8 years) using a probe inserted into the ear canal. This RF was used to calculate the area function of the ear canal versus distance along its centerline. Acoustical reflectance was calculated in the frequency domain from the RF, as was the difference in sound pressure level near the tympanic membrane relative to the probe tip. Group responses in area function, total ear-canal length, absorbance and group delay, and admittance magnitude and phase were analyzed based on sex, ear, and age. Responses were compared between children/adults and younger/older adults relative to age 50 years. Ear and sex were never significant. Significant differences were observed in children compared to adults in the area function, absorbance and group delay, and admittance magnitude and phase (0.25-4 kHz). Group delay differed between younger and older adults. A second experiment assessed level dependence of responses to better understand limitations in probe performance observed in the main experiment. These results show the utility of time-domain measurements of the area function and derived reflectance to understand sound-transmission differences across age at frequencies important to middle-ear function.

Effect of the magnitude of abrupt change in sound pressure on the magnitude and phase synchrony of 40-Hz auditory steady state response

A periodic sound with a fixed inter-stimulus interval elicits an auditory steady-state response (ASSR). An abrupt change in a continuous sound is known to affect the brain’s ongoing neural oscillatory activity, but the underlying mechanism has not been fully clarified. We investigated whether and how an abrupt change in sound intensity affects the ASSR. The control stimulus was a train of 1-ms clicks with a sound pressure level (SPL) of 70 dB at 40 Hz for 1000 ms. In addition to the control stimulus, we applied six stimuli with changes consisting of a 500-ms train at 70 dB followed by a 500-ms similar train with louder clicks of 75, 80, or 85 dB or weaker clicks of 55, 60, or 65 dB. We obtained the magnetoencephalographic responses from 15 healthy subjects while presenting the seven stimuli randomly. The two-dipole model obtained for the 40-Hz ASSR in the control condition was applied to all of the stimulus conditions for each subject, and then the time–frequency analysis was conducted. We observed that both the amplitude and the inter-trial phase coherence of the 40-Hz ASSR transiently decreased and returned to the steady state after the change onset, i.e., the desynchronization of 40-Hz ASSR. The degree of desynchronization depended on the magnitude of the change regardless of whether the sound intensity increased or decreased, which might be a novel neurophysiological index of cerebral response driven by a change in the sensory environment.

Cardiorenal Benefit of Tirzepatide in Type 1 Diabetes: A Case Report

Abstract Patients with type 1 diabetes (T1D) who are obese are at risk of cardiovascular disease, renal diseases, and other complications. Unfortunately, there is currently no cure for T1D, necessitating individuals with this condition to rely on lifelong insulin therapy. Tirzepatide, a dual-acting glucose-dependent insulinotropic polypeptide/glucagon-like peptide-1 agonist, has recently been approved for treating type 2 diabetes. We report the case of a 38-year-old male who presented with T1D, stage 2 chronic kidney disease, obesity, and other comorbidities. He was prescribed tirzepatide 2.5 mg initially, followed by titration up to 5 mg. A significant reduction in blood glucose levels, weight, and microalbumin levels was observed. Additionally, the systolic blood pressure level was also seen to improve. These results highlight new indications of tirzepatide in managing T1D and obesity. However, further studies are warranted to explore its efficacy and safety in patients with T1D.

Data-driven multi-objective optimization of aerodynamics and aeroacoustics in dual Savonius wind turbines using large eddy simulation and machine learning

Savonius rotor is a popular form of vertical-axis wind turbine (VAWT) for small-scale and urban applications because of its straightforward design and self-starting ability. Dual VAWTs present challenges in terms of wake interactions and noise, particularly in urban areas. Optimizing these parameters is essential for future wind energy adoption. This research is the first to analyze how the interaction of wakes from adjacent rotors, combined with a deflector, affects both the aerodynamic performance and noise levels of dual Savonius rotors. Large Eddy Simulation is applied, as it effectively captures detailed turbulent wind flows and their interactions with wind turbines. A multi-objective optimization method combining Machine Learning and Computational Fluid Dynamics (CFD) is developed to optimize rotors for maximum power efficiency and minimum noise, considering their wake interactions with a unique deflector system. First, the influence of geometric parameters on aerodynamics and aeroacoustics characteristics of rotors is analyzed, and the database is generated using Design of Experiment approach. Next, the CFD model is replaced by Artificial Neural Network (ANN) model established for predicting rotor performances. A Multi-Objective Genetic Algorithm method is used to optimize aerodynamics and aeroacoustics characteristics of rotors. Finally, optimal design parameters are identified from the Pareto front using the technique for order of preference by similarity to ideal solution decision-making method. The ANN model demonstrated high accuracy with an RANN2 of 0.995 and 0.971 for the average power coefficient (CP) and overall sound pressure level (OSPL) predictions, respectively. Multi-objective optimization revealed the best configuration of the deflector with bleed jets, improving the average CP up to 57.5% and reducing OSPL to an almost 5.2% compared to the dual rotor case at TSR = 0.8.

Quantitative in-vitro assessment of a novel robot-assisted system for cochlear implant electrode insertion.

As an increasing number of cochlear implant candidates exhibit residual inner ear function, hearing preservation strategies during implant insertion are gaining importance. Manual implantation is known to induce traumatic force and pressure peaks. In this study, we use a validated in-vitro model to comprehensively evaluate a novel surgical tool that addresses these challenges through motorized movement of a forceps. Using lateral wall electrodes, we examined two subgroups of insertions: 30 insertions were performed manually by experienced surgeons, and another 30 insertions were conducted with a robot-assisted system under the same surgeons' supervision. We utilized a realistic, validated model of the temporal bone. This model accurately reproduces intracochlear frictional conditions and allows for the synchronous recording of forces on intracochlear structures, intracochlear pressure, and the position and deformation of the electrode array within the scala tympani. We identified a significant reduction in force variation during robot-assisted insertions compared to the conventional procedure, with average values of 12mN/s and 32mN/s, respectively. Robotic assistance was also associated with a significant reduction of strong pressure peaks and a 17dB reduction in intracochlear pressure levels. Furthermore, our study highlights that the release of the insertion tool represents a critical phase requiring surgical training. Robotic assistance demonstrated more consistent insertion speeds compared to manual techniques. Its use can significantly reduce factors associated with intracochlear trauma, highlighting its potential for improved hearing preservation. Finally, the system does not mitigate the impact of subsequent surgical steps like electrode cable routing and cochlear access sealing, pointing to areas in need of further research.

Acoustic comfort in primary- and nursery-school canteens: From measurements to recommendations

Canteens usually have critical acoustic conditions resulting from the need to maximize the number of occupants while minimizing volume. Thus, in the absence of specific sound absorbing treatments, very high sound pressure levels are usually observed resulting in significant impairment of communication (with increased vocal effort of speakers and reduced speech intelligibility), and dangerously high exposure levels for workers. The present paper reports acoustic measurements carried out in a nursery school canteen having a volume of 212 m3 and seating about 50 children, and two primary school canteens having volumes of 656 m3 (seating 150 children) and 367 m3 (seating 107 children). Reverberation time was measured in each room as well as sound pressure levels during peak occupation (averaged over 15-minute intervals), resulting in A-weighted sound pressure levels spanning between 81 dB (in the nursery school) and 90 dB in the primary schools. Starting from the observed values, considerations about the group-size of the occupants as a function of age were made, and recommendations were finally given to guide the acoustic correction of similar spaces.