A-weighted Sound Level Research Articles

Starship super heavy acoustics: Far-field noise measurements during launch and the first-ever booster catch.

Far-field (9.7-35.5 km) noise measurements were made during the fifth flight test of SpaceX's Starship Super Heavy, which included the first-ever booster catch. Key results involving launch and flyback sonic boom sound levels include (a) A-weighted sound exposure levels during launch are 18 dB less than predicted at 35 km; (b) the flyback sonic boom exceeds 10 psf at 10 km; and (c) comparing Starship launch noise to Space Launch System and Falcon 9 shows that Starship is substantially louder; the far-field noise produced during a Starship launch is at least ten times that of Falcon 9.

Best descriptors for predicting noise annoyance and spectrum-based penalty of steady-state wideband noise

Many objective descriptors (i.e., single-number quantities) are available in the literature for the objective assessment of noise annoyance of wideband, steady-state sounds. However, there is no definitive understanding of which descriptors best correspond to subjective annoyance. Our purpose is to assess how different descriptors correspond with differences in noise annoyance resulting from changes in A-weighted sound level and spectrum. This investigation is based on recently published results from a psychoacoustic experiment conducted by Kuusinen et al. [1]. They investigated 23 steady-state wideband noises with various spectral shapes within 32-48 dB LAeq, and participants rated them in terms of subjective annoyance. The study revealed that penalty due to spectrum shape could be even 10 dB. Here, we present a follow up analysis focusing on objective noise descriptors. The results indicate that many descriptors are strongly associated with noise annoyance ratings, while Spectral Centroid and Sharpness appear to be the best candidates to predict spectrum-based penalty.

Virtual assessment of phone booths' acoustic performance in laboratory and office environments

The irrelevant speech noise is one of the significant issues affecting workers' productivity and comfort. Acoustic furniture is the most common solution addressing this problem: mobile phone booths and partially closed workstations are two examples. The acoustic performance of such devices is defined with laboratory tests according to ISO 23351-1:2020. The sound power level measured in reverberation rooms with and without the product determines the reduction of speech A-weighted sound power level (DS,A). However, predicting acoustic performance in real-world scenarios is still challenging. The present work explores the discrepancies between DS,A, and apparent speech reduction (D'S,A) through numerical models. The study assesses the performance difference between a calibrated virtual reverberation room and virtual open-plan offices maintaining the same acoustic properties, i.e., sound transmission and sound absorption, of a typical two-person phone booth. Moreover, the study investigates the fluctuation on D'S,A changing main room acoustic criteria, e.g., the reverberation time (T) and the total absorption area (A). Results help define ray-based simulations' reliability in predicting furniture ensembles' acoustic performance.

Noise monitoring in primary schools: comparisons between different time-dependent parameters for acoustic performance evaluation

The A-weighted equivalent sound level is commonly used to describe or regulate environmental noise over a defined time interval. Although it is very convenient and easy to compare noise limits or requirements, it does not provide summary information on how noise evolves. On the other hand, the detailed analysis of the history of the measurements over time is too burdensome in the case of long-term monitoring. As part of a large study that aims to investigate the effects of noise on the cognitive abilities of primary school children, long-term unattended monitoring was carried out using low-cost instrumentation based on smartphone apps and calibrated external microphones. From the data obtained, acoustic indices and parameters were calculated, which allowed the assessment of the time-dependent noise exposure of the students based on the type of activity carried out in class. This analysis can be useful for validating the acoustic design requirements in schools.

Weight minimization of train floors with acoustic and structural constraints

For high-speed trains, high noise levels are generated in the bogie from wheel-rail contact and aero-acoustic sources. Manufacturers try to minimize the floor transmission to the interior, e.g. by applying damping layers or by other measures. For vehicle noise control measures, the goal is often to achieve the sound reduction needed at lowest possible mass. Here, an optimization scheme is applied to minimize the mass of an extruded floor panel. Constraints are defined by limiting the maximum local floor deflection from passenger loads according to EN 12663-1 and the A-weighted interior sound level. Recognizing the periodic nature of the floor structure, a Finite Element model of a single periodic cell is set up, using periodic boundary conditions and the floor sound reduction is determined using a Statistical Energy Analysis approach. An analytic beam model is applied to determine the floor deflection from the passenger load. Design solutions meeting the constraints with the smallest possible mass are sought. Starting with a floor structure with 23.3 kg/m2, a final design with 18.0 kg/m2 is reached. In addition, the transmitted sound through the floor is reduced by 8 dBA. Convergence from different starting points is verified.

Enhancing autumn greenway walking experience: Exploring the combined effects of noise and thermal environment.

The evaluation of outdoor green spaces is influenced by diverse sensory perceptions. Traffic noise and thermal conditions significantly impact greenway-walking satisfaction; their optimization is vital for improving user experience and encouraging outdoor engagement. The study examines a typical Beijing greenway during autumn, focusing on strategies to enhance the walking experience under the combined effects of noise and thermal environments through mobile measurements and surveys. The results show that: 1) The interplay between noise and thermal factors varies depending on the walking state. Upon arrival, an increase in noise significantly worsens thermal comfort; higher sound levels intensify warm thermal sensations, though this effect is not consciously perceived. Upon departure, the effect of noise on thermal perception is not obvious. In both walking states, thermal sensation significantly affects subjective noise perception, yet the trends of influence differ. Subjective noise loudness increases as thermal comfort worsens, showing significant correlation only upon departure. 2) During autumn greenway walks, acoustic factors exert a greater impact on Overall Environmental Satisfaction (OES), with subjective noise loudness being more influential than noise level, followed by air temperature (Ta). Greater noise decreases OES, while OES increases initially with Ta and then decreases. The integrated effects of noise-thermal factors on OES show significant changes. 3) To enhance the autumn greenway-walking experience, the advised parameters are A-weighted Sound Level (ASL) ≤ 59.12 dBA and 15.17°C ≤ Ta ≤ 18.75°C. Finally, three design strategies are proposed: reducing subjective noise loudness, differentiating design based on walking status and balancing acoustic-thermal perceptual preferences.

Full of sound and fury.

The subject of noise in the operating theatre was recognized as early as 1972 and has been compared to noise levels on a busy highway. While noise-induced hearing loss in orthopaedic surgery specifically has been recognized as early as the 1990s, it remains poorly studied. As a result, there has been renewed focus in this occupational hazard. Noise level is typically measured in decibels (dB), whereas noise adjusted for human perception uses A-weighted sound levels and is expressed in dBA. Mean operating theatre noise levels range between 51 and 75 dBA, with peak levels between 80 and 119 dBA. The greatest sources of noise emanate from powered surgical instruments, which can exceed levels as high as 140 dBA. Newer technology, such as robotic-assisted systems, contribute a potential new source of noise. This article is a narrative review of the deleterious effects of prolonged noise exposure, including noise-induced hearing loss in the operating theatre team and the patient, intraoperative miscommunication, and increased cognitive load and stress, all of which impact the surgical team's overall performance. Interventions to mitigate the effects of noise exposure include the use of quieter surgical equipment, the implementation of sound-absorbing personal protective equipment, or changes in communication protocols. Future research endeavours should use advanced research methods and embrace technological innovations to proactively mitigate the effects of operating theatre noise.

Amplifying concerns: An exploration of community noise levels in rural communities impacted by wood pellet production

Wood pellets are increasingly promoted as a renewable and sustainable energy source, driving the global wood pellet market to a projected value of $16 billion by 2026. However, the rapid expansion of this industry disproportionately affects predominantly Black and low-income communities in the rural South, where approximately 100 pellet manufacturing plants are currently located in the United States. From August 2023 to March 2024, we conducted a noise exposure assessment in Gloster, Mississippi, a community affected by pellet production, and compared it to Mendenhall, a nearby community without industrial activity. In collaboration with a local organization, we measured noise metrics and found significantly higher A-weighted, C-weighted, and Z-weighted sound levels in Gloster, along with elevated decibels at multiple center frequencies. These findings suggest that wood pellet manufacturing can severely alter the soundscape of rural communities, raising environmental justice concerns. Our findings underscore the importance of investigating the cumulative health impacts of noise and other environmental burdens on these vulnerable communities to better inform policy.

Research on audible noise of ultra-high voltage direct current (UHV DC) transmission lines with a digital twin

Much attention has been paid to audible noise in the design of ultra-high voltage (UHV) direct current (DC) transmission lines because of its negative impact on residents' lives. In order to analyze audible noise, shorten the research period, and reduce experimental costs, firstly, a digital twin model for audible noise of UHV DC transmission lines is proposed. Then, the model’s structure and related principles are explained in detail. Finally, an application, as a research paradigm, uses digital twin to study the source distribution on transmission lines and influencing factors of audible noise. The A-weighted sound level of audible noise on the ground is calculated and compared with the data obtained by the BPA empirical formula. The results show that the position of the sound source tends to have uniform distribution and the intensity tends to have Gaussian distribution. We also used the model to simulate and analyze the effects of temperature and humidity on the generation and propagation of audible noise, illustrating the great value of digital twin technology in the study of audible noise. This paper not only provides a new method for audible noise research, but also provides a reference for the design of UHV DC transmission lines.

An energy-based framework for predicting vehicle noise source intensity: From energy consumption to noise

The vehicle noise source strength prediction model is a crucial component in the field of traffic noise prediction. Despite the establishment of noise source strength localized models in various countries, the theoretical underpinnings of the sound power level models within these frameworks remains unclear. This study addresses this gap by analyzing the correlation between vehicle noise and energy consumption. An energy-based source strength model framework (E-SSIM) is proposed, focusing on developing nonlinear models for basic noise level. E-SSIM is built on acoustical principles and the energy flow of vehicles, integrating noise and energy consumption through the application of multivariate regression theory, characterized by a transient or simplified mathematical framework. Furthermore, sensitivity analysis and road experiments are conducted to validate the proposed framework. The findings reveal that E-SSIM effectively integrates vehicle energy flow and principles of acoustics, thereby providing a theoretical foundation for the logarithmic mathematical structure in classical noise source strength models. The study reveals that in low-speed driving conditions (17–40 km/h), the sensitivity of noise energy to aerodynamic drag energy consumption reaches its peak. Specifically, the sensitivity of E-SSIM, as assessed by the A-weighted sound level, progressively decreases with increasing speed. On the contrary, for the Z-weighted sound level, the sensitivity initially decreases before rising again, reaching its peak stability and robustness at a speed of 23.8 km/h. E-SSIM exhibits superior precision in predicting A/Z-weighted sound pressure levels. Compared to classic logarithmic structural prediction models, the mean absolute percentage error of E-SSIM was reduced by 4.19% and 0.07%. Compared to typical models such as ASJ developed by the Acoustical Society of Japan and CNOSSOS-EU used by the European Commission, E-SSIM yielded a mean absolute percentage error reduction of 68% and 67%. Interestingly, as vehicle internal energy consumption increases, the prediction deviations of E-SSIM, ASJ, and CNOSSOS-EU gradually decrease, possibly because vehicle operating conditions approach stability. E-SSIM can utilize abundant vehicle data to develop generic models, promoting the advancement of noise prediction.

The effects of acoustic-light-thermal environment quality parameters on pedestrians’ overall comforts in residential districts

This study explored subjective responses towards various environmental quality parameters. It would be helpful to approach an overall comfort improvement relating to physics. In order to investigate the combined effects of sound, light and heat on the overall comfort of pedestrians, which could be evaluated by overall comfort vote, two residential areas in Yubei District, Chongqing (a Cfa city in China) were selected for field measurements and questionnaires. Three were three key findings were concluded based on subjective responses to environmental parameters via multiple linear regression. First, the average outdoor neutral temperature, mean neutral sound level and neutral illumination intensity were determined to be 26.6 °C (determined by physiologically equivalent temperature), 56.5 dBA (determined by A-weighted equivalent continuous sound level) and 21.4 klx (determined by LUX), respectively. Second, considering the effects of both physiology and psychology, thermal perceptions varied for acoustic and light environments. Residents partially had lower neutral temperatures at the noisy condition. Third, environmental quality factors had a significant effect on overall comfort. Positive correlation between physiologically equivalent temperature and overall comfort vote was found (sig < 0.000); while the effects of sound pressure and light intensity were not always significant. Hence, thermal stress played a significant role in people’s overall comfort. This study has explored the effects of three environment quality parameters on human perceptions. It provided better understanding against dwellers’ feelings under complex circumstances. Future urban design and planning works should consider the cooling factors regarding contextual acoustical and visual environments.

Forecasting community response to low-frequency noise

The most common approach to managing environmental noise is by reference to A-weighted sound levels deemed appropriate for the community. These criteria are usually derived from transportation noise studies for which the relative proportion of low-frequency noise is implicit. Very different community reactions can arise when source spectra don't represent those studied. Responses diverge even further when the listeners' context also differs from that originally studied. This is nowhere more evident than in the case of large industrial equipment (such as power plants and gas compressor stations) sited in rural areas, due in large part to strong Low-Frequency Noise (LFN). Guidance for forecasting community reaction to LFN is scattered throughout the literature as individual studies employing a diverse assortment of approaches and noise descriptors. The purpose of the present paper is to demonstrate a straightforward, comprehensive, and unified forecasting approach suitable for inclusion in ANSI S12.9 Part 4 "Noise Assessment and Prediction of Long-Term Community Response", similar in many respects to the method recently deleted from this standard (2005 Annex D).

A year of background sound measurements in suburbia

An internal research project was undertaken to measure the background sound levels at one location with the same equipment for a full year. A suitable location was identified to allow the equipment to stay in the same place and available to refresh data memory cards and battery power. The sound monitoring was done from October 2020 through November of 2021. The site selected was a typical suburban residential property near a secondary road, but far from other influencing sources of sound like highways and industry. The data set is over 9,000 hourly samples of A-weighted sound levels. For each hour the L99, L90, L50, L10, L01 and LEQ were recorded and evaluated for this study. This paper addresses the compilation of the year worth of A-weighted sound levels. The data set also includes one-third octave band sound pressure levels, but those data have not been considered in this evaluation. The noted sound metrics have been evaluated by month, day of the week and hour. The paper also evaluates the selection of the lowest background sound level that is used in many noise ordinances, including the author's home state of Massachusetts.

On the expert evaluation of potential damage to hearing using A-weighted sound exposure level (LAE)

On the expert evaluation of potential damage to hearing using A-weighted sound exposure level (LAE)

Background noise and reverberation time in a college classroom

A sound survey of noise levels in unoccupied classrooms on the Marietta Campus of Kennesaw State University identified one classroom as the most problematic in terms of background noise levels. This level is mostly associated with heating, ventilation, and air-conditioning equipment. Excessive background noise in learning spaces diminishes the speech intelligibility from the speaker to the listeners and can cause stress and fatigue. The overall A-weighted average sound levels are compared with ANSI-ASA S12.60-2010/Part 1 (Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools). In addition, frequency analysis of the background sound and time variations are studies. Binaural headset microphone measurements are compared to the single microphone measurements. Reverberation time is measured using the engineering survey method and compared to the ANSI guidelines.

Model calculations and measurements of shooting sound in practical situations

Shooting sound in practical situations with propagation distances up to 300 m is investigated by means of model calculations and measurements. The results illustrate uncertainties in the model calculations for practical situations. The measurements were performed with various small-caliber weapons. Microphones were placed at positions screened by a noise barrier, and also at unscreened positions. The measured signals contain muzzle sound and bullet sound. The model calculations for muzzle sound and bullet sound take into account emission spectra and various propagation attenuation terms, including ground attenuation and barrier attenuation. The bullet sound model is based on a nonlinear theory of N waves generated by supersonic projectiles. For the unscreened situation, model and measurement results show that the sound levels are considerably reduced by ground attenuation. Ground-level variations and ground roughness in the measurement area play an important role. At a 300 m distance, the A-weighted bullet sound level is higher than the A-weighted muzzle sound level, which underlines the importance of bullet sound. For the screened situation, model and measurement results are used to analyze diffraction of bullet sound by the horizontal and vertical edges of the barrier. The diffraction is explained by considering Fresnel zones on the bullet trajectory.

A-weighted sound power level of electric vehicles in accelerating and decelerating conditions

A-weighted sound power level of electric vehicles in accelerating and decelerating conditions

Evaluating the mitigating effects of water sounds on multi-dimensional negative reactions due to secondary radiation noise

People exhibit a range of negative reactions to noise. However, previous study on masking secondary radiation noise focused on its impact on a single negative reaction, namely dissatisfaction. This is a gap in understanding the mechanisms that mitigate multi-dimensional negative reactions (MNR), which encompass various emotional responses to noise, including annoyance, dissatisfaction, and others. Therefore, this study selected four mutually independent critical reactions (subjective loudness, depression, discomfort, and dissatisfaction) and analyzed the masking effects of adding four types of water sounds (fountain, stream, water-drop, and waterfall sounds) on MNR caused by secondary radiation noise. Seventy-nine participants were presented with a series of combined sound samples before casting their votes of MNR in an auditory test booth. The results revealed that adding the four types of water sounds mitigated the MNR induced by secondary radiation noise. Among them, the water-drop sound was the most effective, while the waterfall sound was the least capable. The fountain sound was preferred over the stream sound for optimizing the MNR, focusing on subjective loudness, discomfort and dissatisfaction, which were caused by higher level of combined sound. Furthermore, as global A-weighted sound level (LAeq) increased from 55 to 65 dBA, the mean subjective loudness levels generally remained the highest. Beyond the subjective loudness, when global LAeq increased to 65 dBA, the mean depression level exceeded the mean discomfort level and mean dissatisfaction level when the fountain or water-drop sound was added, whereas the three mean levels remained approximately equal when the stream or waterfall sound was added.

An analytical investigation into noise levels in public health sector neonatal intensive care units in the eThekwini District

Background. Noise is a known environmental stressor in the neonatal intensive care unit (NICU), as it may result in adverse effects on preterm neonates because of the unique vulnerability and physiological immaturity of their central nervous systems. Objective. To investigate noise levels in public sector NICUs in the eThekwini District, KwaZulu-Natal Province, South Africa. Methods. An analytical observational study design with purposive sampling of public sector hospitals was used. Noise was continuously measured with a sound level meter in a central location for 48 hours on 2 consecutive days (Sunday and Monday) in the four NICUs. A sample of noise sources, as well as their frequency of occurrence, was identified through direct observation and a frequency spectrum analysis using one-third octave bands. Data were analysed using descriptive and inferential statistics. Results. This study included one tertiary hospital and three regional hospitals in the eThekwini District. Mean noise levels exceeded international recommendations of an A-weighted equivalent continuous sound level (LAeq) of 45 A-weighted decibel (dBA) and an A-weighted maximum sound level (LAmax) of 65 dBA in all four hospitals. The most frequently occurring sources of noise were staff conversations (30.9%, Hospital A), device alarms (21.0%, Hospital B) and closing metal pedal bins (20.0%, Hospital B). Mean LAeqs &gt;45 BA were found in the mid and high frequencies (250 Hz - 6 300 Hz) in all hospitals, particularly during the afternoon. Conclusion. The findings emphasise the need for continuous noise monitoring, awareness and education among healthcare professionals in the NICU. Future research should expand on existing findings and focus on interventions for noise control in NICUs.

A study examining the long-term effects of aircraft noise on the surrounding residents before the opening of Long Thanh Airport

Long Thanh Airport (LT) is a new airport scheduled to open in 2025 and serve as the largest aviation hub in Vietnam. The residents are expected to experience adverse health effects from long-term noise exposure once LT begins operation. This study aims to serve as a basis for comparing the impact of environmental changes before and after the opening of LT. This study assesses the health of the residents in ten residential areas under the planned flight paths of LT. Currently, before the new airport operates, environmental noise around LT is primarily caused by traffic noise from nearby roads near the selected houses. The 24-hour A-weighted equivalent continuous sound level (LAeq) at a representative house in each area ranged from 51 to 72 dB. In August 2022, 641 residents were surveyed to assess their health conditions. It was found that traffic noise was the most frequently cited environmental nuisance among the surveyed participants. However, the regression model considers contextual factors, noise exposure, and other factors impacting health and indicates that the health of the residents is associated with factors beyond noise exposure, such as noise sensitivity, mobility, and attitude towards transport modes.