Search Results (57)

Synthetic jet actuators are becoming increasingly popular for enhancing electronic heat transfer. However, their use is currently limited due to the high noise they generate. This article examines how actuator parameters (orifice diameter, orifice length and cavity height) affect synthetic jet velocity and noise generation. Hot-wire anemometry was used to measure velocity, and noise was measured with a sound meter. The actuator was supplied with constant power at different frequencies ranging from 50 to 500 Hz. Observation of the velocity showed that it decreased with an increasing orifice diameter and increased with a decreasing orifice length. No relationship was observed between cavity height and synthetic jet velocity. This article indicates that increasing the orifice diameter or reducing the orifice length causes an increase in the noise generated by SJAs, provided we remain in the vicinity of the characteristic frequency. It was demonstrated that higher actuator chambers produce higher noise levels, although this was not a consistent trend across the entire tested frequency range. Full article

Material removal processes such as milling, drilling, and turning often generate harmful vibrations that can negatively impact both machine performance and operator safety. Addressing these vibrations at their source or reducing them to safe levels is, therefore, a critical challenge. This study proposes a practical solution by introducing thin-fin-type vibration-absorbing devices fabricated using 3D printing technology. These devices are designed specifically to mitigate vibration propagation during milling operations. To evaluate their effectiveness, a multi-sensor system comprising sound level meters, a vibrometer, and a vision–acoustic camera was employed to measure sound levels. The results show that the use of fabricated devices can reduce noise levels significantly, from 93 dB (comparable to power tools or a lawn mower) to 74 dB (similar to normal conversation or a busy office). This substantial reduction demonstrates the potential of the proposed devices to enhance workplace safety and acoustic comfort on the shop floor. Full article

Festivals are significant markers of cultural heritage and community traditions. Nevertheless, every year, significant increases in pollution levels are recorded during celebratory events, due to the overuse of firecrackers. This study evaluated gaseous and particulate matter (PM) concentrations using a gas and particulate sampler, alongside noise levels measured by a sound level meter, during the pre-to-post-Diwali period of 2023 and 2024 in Malda, India, and PM concentrations in Warsaw, Poland in 2024, using a DustAir dust meter. The results indicated that during Diwali, the concentrations of PM_2.5 and PM₁ exceeded the standard set by the World Health Organization, while gaseous pollutants remained within acceptable limits. Since no standards set for PM₁ exist, PM_2.5 criteria were utilized as a benchmark. Additionally, on New Year’s Eve in Warsaw, concentrations of PM₁₀, PM_2.5, and PM₁ surpassed the standard around midnight, while gaseous pollutants remained within the standard range. An elemental analysis revealed 13 elements in Diwali PM samples, with toxic metals like arsenic and cadmium more prevalent in PM₁. The risk of carcinogenic and non-carcinogenic effects through ingestion was higher for children compared to adults. The findings of this study could potentially raise awareness among researchers and policymakers, prompting them to develop sustainable substitutes for firecrackers and sparklers. Full article

Background/Objectives: Effective communication in critical care is crucial, particularly with the constraints of Personal Protective Equipment (PPE). This study aimed to evaluate speech intelligibility under varying conditions of distance, ambient noise, and PPE types in a simulated ICU. Methodology: A quasi-experimental design was used with 23 participants in 24 scenarios, combining three distances (1, 2, and 5 m), two noise levels (quiet and ICU-like), and four PPE types (no mask, surgical mask, N95, and PAPR). Speech intelligibility was assessed by positioning the subjects at varying distances while playing phonetically balanced words through a playback device equipped with the different PPE being tested. The evaluation was conducted under two sound conditions (25 dB(A) and 45 dB(A)). The percentage of correct responses by the subjects to the perceived sounds was determined as a measure of intelligibility. The relation between variables was analyzed using the Wilcoxon Test and the Friedman Test. Results: Significant differences in word recognition were observed across conditions. Ambient noise reduced intelligibility, with recognition percentages significantly lowering in noisy environments. PPE type also influenced comprehension, with PAPR posing the greatest challenge. Friedman’s test showed that increasing distance significantly decreased recognition accuracy. Distances beyond two meters negatively impacted intelligibility across all devices tested. Conclusions: In noisy conditions (>45 dB(A)), a combination of distances greater than two meters and PPE use reduced intelligibility by over 40%, potentially compromising patient safety. The use of communication aids, such as visual cues or alternative speech devices, is recommended, particularly with PAPRs, to enhance comprehension and ensure effective communication between healthcare providers and patients. Full article

Flight line personnel are constantly exposed to noise and jet fuel while working on flight lines. Studies suggest that jet fuel in combination with noise affects hearing loss more than noise exposure alone. This study examined the combined effects of jet fuel and noise exposure on the hearing of flight line personnel stationed at Japan Air Self-Defense Force Air Bases (Hamamatsu, Matsushima, Hyakuri, Yokota, and Iruma) and US Air Force Air Bases (Kadena and Misawa) in Japan. Samples were collected from all participants, 97 flightline-exposed and 71 control volunteers, to measure their individual noise levels with a personal sound level meter and volatile organic chemicals (VOCs) with a chemical sampling pump during a single shift. Blood samples were collected post shift. Urine samples (entire void) were collected prior to the shift (morning first void) and post shift. VOCs were measured in air, blood, and urine. An audiometric test battery, consisting of immittance measurements, audiograms, distortion product otoacoustic emissions, and the auditory brain response, was conducted after the shift to examine the hearing of participants. Total VOCs in personal air samples were in the ppb range for each group. Tinnitus and temporary hearing loss were reported in audiological histories but were also present in some controls. Noise levels on the flight line were greater than the action level for requiring hearing protection and exceeded exposure limits, but all exposed subjects reported wearing hearing protection. Audiometric tests identified significant differences and trends between flight line and control personnel, indicating the potential for hearing disorders. In spite of very low levels of VOC exposure and wearing hearing protection for noise, there is still the potential for hearing issues in flight line personnel. Full article

In this paper, the development of a low-cost acoustic sensor is presented based on an import-substituting element base as a cheap alternative to professional sensors or analog sensors. An Arduino board, a microphone module, a microSD card module, and other modules were used. To improve the accuracy of the data taken from the microphone, it was calibrated using a reference noise meter, using a logarithmic smoothing method to calculate the sound level in decibels, and an equation was formulated for converting the obtained ADC values into decibels. The code of the program executed by the sensor was developed and sewn into the device. The data captured from the microphone are stored in a CSV file with the date and time of the captured data. Full article

Eco-acoustic indices allow us to rapidly evaluate habitats and ecosystems and derive information about anthropophonic impacts. However, it is proven that indices’ values and trends are not comparable between studies. These incongruences may be caused by the availability on the market of recorders with different characteristics and costs. Thus, there is a need to reduce these biases and incongruences to ensure an accurate analysis and comparison between soundscape ecology studies and habitat assessments. In this study, we propose and validate an audio recording equalization protocol to reduce eco-acoustic indices’ biases, by testing three soundscape recorder models: Song Meter Micro, Soundscape Explorer Terrestrial and Audiomoth. The equalization process aligns the signal amplitude and frequency response of the soundscape recorders to those of a type 1 level meter. The adjustment was made in MATLAB R2023a using a filter curve generated comparing a reference signal (white noise); the measurements were performed in an anechoic chamber using 11 audio sensors and a type 1 sound level meter (able to produce a .WAV file). The statistical validation of the procedure was performed on recordings obtained in an urban and Regional Park (Italy) assessing a significant reduction in indices’ biases on the Song Meter Micro and Audiomoth. Full article

The increase in industrial activities has raised concerns regarding air quality in urban areas within Malawi. To assess the source apportionment of air quality parameters (AQPs) and noise levels, concentrations of AQPs (CO, TSP, PM _2.5, PM₁₀) and noise levels were monitored at 15 sites in Makata, Limbe, Maselema, Chirimba, and Maone during dry and wet seasons, respectively. Active mobile multi-gas monitors and a Dylos DC1100 PRO Laser Particle Counter (2018 model) were used to monitor AQPs, while Integrated Sound Level Meters were used to measure noise levels. Monitoring and analysis were guided by the World Health Organization (WHO) and Malawi Standards (MS). A Positive Matrix Factorization (PMF) model was used to determine the source apportionment of AQPs, and matrix trajectories analysed air mass movement. In the wet season, the average concentration values of CO, TSP, PM₁₀, and PM_2.5 were 0.49 ± 0.65 mg/m³, 85.03 ± 62.18 µg/m³, 14.65 ± 8.13 µg/m³, and 11.52 ± 7.19 µg/m³, respectively. Dry season average concentration values increased to 1.31 ± 0.81 mg/m³, 99.86± 30.06 µg/m³, 24.35 ± 9.53 µg/m³, and 18.28 ± 7.14 µg/m³. Noise levels remained below public MS and WHO standards (85 dB). Positive correlations between AQPs and noise levels were observed, strengthening from weak in the dry season to moderately strong in the wet season. PMF analysis identified key factors influencing AQP accumulation, emphasizing the need for periodic sampling to monitor seasonal pollution trends, considering potential impacts on public health and environmental sustainability. Further studies should look at factors affecting the dynamics of PMF in Blantyre City. Full article

Road traffic noise is a severe environmental hazard, to which a growing number of dwellers are exposed in urban areas. The possibility to accurately assess traffic noise levels in a given area is thus, nowadays, quite important and, on many occasions, compelled by law. Such a procedure can be performed by measurements or by applying predictive Road Traffic Noise Models (RTNMs). Although the first approach is generally preferred, on-field measurement cannot always be easily conducted. RTNMs, on the contrary, use input information (amount of passing vehicles, category, speed, among others), usually collected by sensors, to provide an estimation of noise levels in a specific area. Several RTNMs have been implemented by different national institutions, adapting them to the local traffic conditions. However, the employment of RTNMs proves challenging due to both the lack of input data and the inherent complexity of the models (often composed of a Noise Emission Model–NEM and a sound propagation model). Therefore, this work aims to propose a methodology that allows an easy application of RTNMs, despite the availability of measured data for calibration. Four different NEMs were coupled with a sound propagation model, allowing the computation of equivalent continuous sound pressure levels on a dataset (composed of traffic flows, speeds, and source–receiver distance) randomly generated. Then, a Multilinear Regressive technique was applied to obtain manageable formulas for the models’ application. The goodness of the procedure was evaluated on a set of long-term traffic and noise data collected in a French site through several sensors, such as sound level meters, car counters, and speed detectors. Results show that the estimations provided by formulas coming from the Multilinear Regressions are quite close to field measurements (MAE between 1.60 and 2.64 dB(A)), confirming that the resulting models could be employed to forecast noise levels by integrating them into a network of traffic sensors. Full article

Aviation is a vital modern transportation sector connecting millions of passengers globally. Sustainable aviation development holds substantial community benefits, necessitating effective management of its environmental impacts. This paper addresses the need for an accurate and cost-effective aircraft noise monitoring model tailored to non-towered general aviation airports with limited resources for official air traffic data collection. The existing literature highlights a heavy reliance on air traffic data from control facilities in prevailing aircraft noise modeling solutions, revealing a disparity between real-world constraints and optimal practices. Our study presents a validation of a three-stage framework centered on a low-cost transponder unit, employing an innovative experimental and analytical approach to assess the model’s accuracy. An economical Automatic Dependent Surveillance-broadcast (ADS-B) receiver is deployed at Purdue University Airport (ICAO Code: KLAF) to estimate aircraft noise levels using the developed approach. Simultaneously, a physical sound meter is positioned at KLAF to capture actual acoustic noise levels, facilitating a direct comparison with the modeled data. Results demonstrate that the developed noise model accurately identifies aircraft noise events with an average error of 4.50 dBA. This suggests the viability of our low-cost noise monitoring approach as an affordable solution for non-towered general aviation airports. In addition, this paper discusses the limitations and recommendations for future research. Full article

The hand-held power sander is a frequently used tool in woodworking, and it is a significant source of risk in terms of dust, vibration, and, notably, noise. The purpose of a hand-held power sander manufacturer’s noise emission statement is to provide information that is useful for assessing the risks associated with noise exposure and should assist users in selecting a hand-held power sander with reduced noise emissions. The stated levels of emitted noise obtained in accordance with a harmonized test procedure may not, in all circumstances, give a reliable indication of the actual risk of noise exposure during the typical use of a hand-held power sander. The aim of this work was to investigate the difference between the values declared by the manufacturers of hand-held power sanders and the measured noise values during actual use. The measurements of the equivalent sound pressure levels were carried out using an integrating–averaging sound level meter (B&K, model 2245) during the sanding of beech and spruce wood with different types of hand-held electric sanders (belt, random orbital, and orbital) with abrasives of coarse, medium, or fine grit. Upon comparing the measured and declared noise values, differences ranging from −6.3 dB to 19 dB(A) were identified for distinct sander types. The results of this study show that the use of declared noise emission values during risk assessments underestimates the magnitude of operator noise exposure. Full article

This paper presents a procedure for the comparison of two technologies developed to classify peach trees according to their nutritional status. The first technology uses the leaf SPAD-502 meter value to characterize tree classes as indicated by agronomist experts: sound, intermediate, and strong chlorosis trees. It is used as a reference for the second technology, which uses a combination of two multispectral indexes computed from reflectance hyperspectral images. Specifically, R_NDVI = (R800 − R670)/(R800 + R670) and HyperSPAD = (R940/R650) are computed for each leaf pixel. An automated methodology is proposed that sets two optical thresholds (three hyperspectral categories) in view of the outliers according to a normal distribution, together with an iterative optimization of the bounding that determines the best assignment of trees to one of the three SPAD_502 levels of nutritional status, as required for practical agronomical purposes such as fertilization. The Chi 2 distribution is used to confirm the similarity of both nutritional classifications. These results encourage the use of on-board multispectral cameras to monitor the nutritional status of trees and to establish a more efficient fertilization strategy where inputs are applied according to individual status, with the consequent reduction in losses of fertilizers such as nitrogen to the atmosphere, soil, and water resulting from over-application. Full article

The Church is a place of worship for Christians; to ensure the smooth and solemn implementation of worship activities, many factors that affect their overall effectiveness must be considered, and one of the conditions that must be met in the worship room is audial comfort. Certain churches are situated in noisy surroundings, which may impact the comfort and auditory experience of worshippers during prayer. This research examines the issue of audial comfort in a church positioned at the periphery of a cross-town road. The main goal of this research was to determine the audial quality deemed comfortable in the Java Christian Church in Bandung from the noise impact caused by high vehicle traffic. The prominent noise that arises from the highway is mostly caused by motorized vehicles. The methodology employed in this study involves a case study approach using quantitative descriptive analysis to evaluate the audial quality of the church. This study uses the Decibel X Sound Meter application to collect data through field measurements. The measured data were analyzed using NoiseTools and IBANA-Calc software was used to analyze the level of noise around the outer church buildings, which are directly adjacent to the main road. The standards used as research references are based on the Decree of the State Minister for the Environment, Number KEP-48/MENLH/11/1996, concerning environmental noise, and the US Department of Housing and Urban Development guidelines regarding spatial noise. Based on the observations made in this research, the noise level within the premises of the Java Christian Church in Bandung is fairly good, so the only addition needed is a barrier that can reduce environmental noise in the Java Christian Church in Bandung. Full article

In the context of urban sustainable development and the creation of pedestrian-friendly campus environments, optimizing campus walking spaces has emerged as a central focus in urban planning research. Presently, research in pedestrian environments predominantly adopts a macroscopic perspective, offering limited insights into pedestrians’ subjective experiences and emotional perceptions at a micro level. Therefore, this study conducted on-site experiments in 21 walking spaces across three campuses, utilizing image semantic analysis, multifunctional sound level meter, wearable electrocardiography devices, and the Profile of Mood States (POMS) to collect data separately on audio-visual environmental factors and pedestrians’ emotional states. This study’s findings revealed significant correlations (p < 0.01) among factors such as the Green Visual Index, Spatial Enclosure Index, Sky Visibility Index, Spatial feasibility Index, and Equivalent Continuous A-weighted Sound Pressure Level with physiological and psychological alterations in pedestrians’ emotions. Additionally, the various proportions of audio-visual environmental factors also exerted significant influences on emotions (p < 0.05). The relevant conclusions can provide a reference for optimizing the audio-visual environment of walking space and promoting the sustainable development of the campus. In future research, the effects of audio-visual environments on both emotional and physiological indicators, as well as subjective evaluations, can be explored further. Full article

Noise levels in a dental office can be produced by different specialty instruments. Exposure to high levels of noise (unwanted sounds) may cause auditory and non-auditory health problems in dentists. The aim of this study was to (a) measure the noise levels within different clinics and laboratories of the Department of Dentistry, School of Health Sciences of the National and Kapodistrian University of Athens, (b) promote information sharing on this serious health issue among stakeholders, and (c) collect data to organize preventive measures for students and personnel (faculty members, collaborators, administrative, and technical staff). Since the study did not apply to acoustics and acoustic measurements, a digital sound level meter and noise-integrating dosimeters with an analogue electronic transducer were used to collect data from certain postgraduate (PG) and undergraduate (UG) clinics and laboratories (LAB) during peak working periods and with a duration of 1 h per clinic/lab. Both personal (dosimeters) and static (area monitoring) noise exposure assessments were evaluated, resulting in various teaching-related activities in dental clinics. At all locations, the maximum exposure limit value of 87 dB(A) was not exceeded. However, chairside personal measurements during ultrasonic work revealed that the lower exposure action value of 80 dB(A) was exceeded. PG clinics were noisier than UG. LAB training settings, even with the new equipment, were close to the upper exposure limit due to the simultaneous use of airotors. In this context, targeted research and investigations into measures are proposed to safeguard the health and safety of students during their duties at the dental school. Full article