Acoustic Noise Level Research Articles

Evaluation of Acoustic Noise Level and Impulsiveness Inside Vehicles in Different Traffic Conditions.

Recently, the issue of sound quality inside vehicles has attracted interest from both researchers and industry alike due to health concerns and also to increase the appeal of vehicles to consumers. This work extends the analysis of interior acoustic noise inside a vehicle under several conditions by comparing measured power levels and two different models for acoustic noise, namely the Gaussian and the alpha-stable distributions. Noise samples were collected in a scenario with real traffic patterns using a measurement setup composed of a Raspberry Pi Board and a microphone strategically positioned. The analysis of the acquired data shows that the observed noise levels are higher when traffic conditions are good. Additionally, the interior noise presented considerable impulsiveness, which tends to be more severe when traffic is slower. Finally, our results suggest that noise sources related to the vehicle itself and its movement are the most relevant ones in the composition of the interior acoustic noise.

Comparison of contrast-enhanced T1-weighted imaging using DANTE-SPACE, PETRA, and MPRAGE: a clinical evaluation of brain tumors at 3 Tesla.

We aimed to compare the performance of three contrast-enhanced T1-weighted three-dimensional (3D) magnetic resonance (MR) sequences to detect brain tumors at 3 Tesla. The three sequences were: (I) delay alternating with nutation for tailored excitation sampling perfection with application-optimized contrasts using different flip angle evolution (DANTE-SPACE), (II) pointwise encoding time reduction with radial acquisition (PETRA), and (III) magnetization-prepared rapid acquisition with gradient echo (MPRAGE). This study involved 77 consecutive patients, including 34 patients with known primary brain tumors and 43 patients suspected of intracranial metastases. All patients underwent each of the three sequences with comparable spatial resolution and acquisition time post-injection. Signal-to-noise ratios (SNRs) for gray matter (GM) and white matter (WM), contrast-to-noise ratios (CNRs) for lesion/GM, lesion/WM, and GM/WM were quantitatively compared. Two radiologists determined the total number of enhancing lesions by consensus. Intraclass correlation coefficients (ICCs) between the two radiologists for metastases presence, qualitative ratings for image quality, and acoustic noise level of each sequence were assessed. Among the three sequences, SNRs and CNRs between lesions and surrounding parenchyma were highest using DANTE-SPACE, but CNRWM/GM was the lowest with DANTE-SPACE. SNRs for PETRA images were significantly higher than those for MPRAGE (P<0.001). CNRs between lesions and surrounding parenchyma were similar for PETRA and MPRAGE (P>0.05). Significantly more brain metastases were detected with DANTE-SPACE (n=94) compared with MPRAGE (n=71) and PETRA (n=72). The ICCs were 0.964 for MPRAGE, 0.975 for PETRA, and 0.973 for DANTE-SPACE. Qualitative scores for lesion imaging using DANTE-SPACE were significantly higher than those obtained with PETRA and MPRAGE (P=0.002 and P=0.004, respectively). The acoustic noise level for PETRA (64.45 dB) was significantly lower than that for MPRAGE (78.27 dB, P<0.01) and DANTE-SPACE (80.18 dB, P<0.01). PETRA achieves comparable detection of brain tumors with MPRAGE and is preferred for depicting osseous metastases and meningeal enhancement. DANTE-SPACE with blood vessel suppression showed improved detection of cerebral metastases compared with MPRAGE and PETRA, which could be helpful for the differential diagnosis of tumors.

Разработка комплекса рекомендаций по повышению экологической безопасности агроэкосистемы

Within the framework of the study, a set of recommendations was developed to reduce the anthropogenic load based on determining the negative impact of the production activities of the agroecosystem (trellis-dwarf intensive garden) in the Kabardino-Balkarian Republic on the state of the environment, the comfort of living and the health of the population. When determining the main measures to optimize the functioning of the agroecosystem, the parameters of the ecological state of the areas of the agroecosystem under study were evaluated, the functional use of the territory at the location of the agroecosystem was analyzed, the level of atmospheric pollution was calculated and analyzed, as well as the level of acoustic (noise) effects on atmospheric air as a result of the production activities of the agroecosystem.

Association of Fear and Annoyance with Acoustic Levels of Dental Equipment Among Adolescents Attending Rural Dental Health Center: A Cross-sectional Study

Introduction: Noise is increasingly becoming pervasive in occupational health concerning practicing dentists as well as patients. A stimulus such as noise from dental equipment compared to anxiety is often multifactorial and can result from a combination of fear of pain, dental instruments noise, or even upcoming negative events and future threats. Aim: This study aimed to assess fear and annoyance levels among adolescents attending a rural dental health centre and compare the acoustic noise levels of dental equipment and its association with fear and annoyance levels among adolescents. Methods: The acoustic noise spectra originating from different tools/equipment in a rural dental health centre is assessed using an application named sound meter of a standard mobile android phone (Samsung galaxy grand 2). Following a 15-minute treatment, a questionnaire was filled by a professional investigator through personal interviews with all subjects. The data is subjected to analysis by Statistical Package for Social Sciences version 22.0. Results: 61.5% of the subjects felt anxious about the anticipatory dental visit, and there was a significant difference observed between genders. Chi-square analysis revealed no significant differences in the fear and annoyance with increasing noise levels in various treatment groups. (p&gt; 0.05). Conclusion: In the present study, fear and annoyance levels increased with increasing noise levels of equipment. Annoyance was found to be significantly higher in females.

The low acoustic noise and turbulence wind tunnel of the University of Sao Paulo

AbstractThis paper introduces the Low Acoustic Noise and Turbulence (LANT) wind tunnel of the Sao Carlos School of Engineering, University of Sao Paulo (USP-EESC), Brazil. The closed-loop wind tunnel features several devices to improve flow uniformity, reduce swirl, and lower the background acoustic noise and turbulence, enabling stability and aeroacoustic experiments. The design criteria was based on the best practices reported, in particular for low turbulence wind tunnels. Yet, these criteria are conflicting and we discuss the decisions that had to be made and present flow quality results that were achieved. The 16-bladed axial fan with 13-blade stators is driven by a variable-speed electric motor. At the corners, 100 mm dense acoustic foam is installed on the vertical walls, floor and ceiling, and the turning vanes are filled with acoustic-absorbing material. The long settling chamber contains a 3.175 mm mesh hexagonal honeycomb and five fine mesh nylon screens, ending in a 7:1 area ratio short contraction. The 3-m long closed-working section has a $1\times 1\ {\rm m}^2$ cross-section area. At 15 m/s the working section wall boundary layer is less than 100 mm thick, providing an area of at least $800\times 800\ \mathrm{mm}^2$ where the streamwise flow uniformity was within 1%. In the 10–30 m/s flow speed range, the turbulence intensity ranged from 0.05% to 0.071% and the background acoustic noise level, obtained with an inflow microphone, ranged from 90 and 110 dB. A benchmark experiment on a flat plate boundary layer produced an almost perfect two-dimensional Blasius profile up to $Re_x \approx 2.5 \times 10^6$ . A beamforming benchmark experiment on aeroacoustics accurately identified the sound emitted by a cylinder immersed in the flow.

The improved automatic control points computation for the acoustic noise level audits

&lt;p class="Abstract"&gt;The acoustic noise level in the interior is one of the quantities specified by a standard and is subject to audits to ensure a comfortable living environment. Currently, the noise level audits are performed manually by a skilled operator, who evaluates the floor plan and uses it to calculate the control points location in which the measurement is performed. The computation is proposed to automate the audit by formulating an optimisation problem for which an algorithm was designed. The algorithm computes the solution that satisfies all constraints specified in the standard, for example, the minimum distance among the control points and fixed obstacles (walls or columns). In the proposed optimisation problem, the fitness function was designed based on the measurement purpose, and two typical use-cases were analysed: (i) long-term stationary noise measurement and (ii) recurring short-term noise measurement. Although the set of control points for both use cases complies with the given standard, it is beneficial to distinguish the location of control points based on the measurement purpose. The number of control points is maximised for the stationary noise and for the immediate coverage area for the short-term noise. The proposed algorithms were tested in a simulation for several floor plans of different complexity.&lt;/p&gt;

Advanced design of Close-Proximity (CPX) trailer enclosure acoustics on tyre/road noise measurement

The PolyU Mark II Twin-wheeled CPX trailer was developed for the measurement of tyre/road noise in Hong Kong urban environment according to a standard methodology (ISO/CD 11819-2) - the Close-Proximity (CPX) method. Numerical simulations of the acoustics of PolyU Mark II CPX enclosure were conducted and a good agreement between numerical and experimental results was obtained. In order to extend the capacity of the Mark II CPX trailer and enhance the acoustic performance within the enclosure for future tyre/road noise studies, the validated numerical simulations were carried on to design the next generation of the PolyU CPX system. Through analyzing the acoustic performance within the enclosures of different dimensions and the distributions of sound pressure level (SPL) inside the anechoic chamber, the geometry of the PolyU Mark III CPX enclosure was finally determined. With newly designed enhanced interior wall absorption, the new PolyU Mark III CPX enclosure design was delivered into numerical simulations for acoustic analysis. Fewer room modes and high uniformity of SPL distributions were observed within the new enclosure design. The PolyU Mark III CPX enclosure was fabricated based on the corresponding dimensions and the specific absorption layers. Great consistency was achieved between the numerical and measured results of the Mark III CPX enclosure. In addition, the PolyU Mark III CPX enclosure shows an improved acoustic property with a lower background noise level during road tests than Mark II CPX enclosure. The outcome of this study firmly establishes the feasibility of designing advanced CPX enclosure with numerical simulations with results that can be realized in realistic CPX measurement.

Assessing traffic noise in teh City of Sharjah using prediction models

Noise originated from traffic on inner-city roads has been recognized as a major issue that has negative effects that go beyond annoyance and adverse health effects on people living near such roads. In this paper, we report the results of employing mathematical models for assessing traffic noise levels near roads in the City of Sharjah, UAE. Our field measurements indicated high noise levels near inter-city roads including roads in residential areas. To further investigate this, measured noise levels arising from principle traffic noise parameters were re-examined using published mathematical models with the objective of validating the acoustic noise levels generated by traffic noise of mixed composition, traffic flow rate and distance from the source. The main sound levels, namely the statistical equivalent sound levels (Leq): L10, L50 and L90 were used in the mathematical predictive models, to calculate the day time sound levels and correlated it with in situ measurements. We have examined 10 linear regression models, reported in the literature, five of which were found to provide strong correlation and were validated for predicting noise arising from traffic. The models are recommended for calculating mixed traffic noise levels and its effects on people living near these inter-city roads.

Development of acoustic mufflers for cabin noise reduction in Orion spacecraft

Controlling cabin acoustic noise levels in the Crew Module (CM) of the Orion spacecraft is critical for adequate speech intelligibility, avoid fatigue, and prevent any possibility of temporary and permanent hearing loss to the crew. The primary source of cabin noise for the on-orbit phase of the mission is from the Environmental Control and Life Support System (ECLSS) which recycles and conditions breathing air and maintains cabin pressurization through its ducting network and components. Unfortunately, as a side effect, noise from the ECLSS fans propagates through theses ducts and emanate into the cabin habitable volume via the ECLSS inlet and outlets. To mitigate excessive duct-borne noise, two ECLSS mufflers have been designed to provide significant acoustic transmission loss (TL) so that the cabin noise requirements can be met. Each muffler is meant to be installed in the ducting of the ECLSS air inlet and outlet sides, respectively. Packaging constraints and tight volume requirements necessitated the mufflers to be of complex geometry and compatible with the bends of the ECLSS duct layout. To design and characterize the acoustic performance of the inlet and outlet mufflers, computational acoustic models were developed using the Finite Element Method (FEM) with software. Characterization of the acoustic material and perforations in the mufflers were addressed with poro-elastic theory. Once the mufflers were designed on paper and its TL predicted, prototypes of these mufflers were created using additive manufacturing. The muffler prototypes were subsequently tested for acoustic TL in the laboratory with various configurations of acoustic materials. Comparing the analytical predictions to the test performance yielded excellent correlation for acoustic TL and demonstrated significant broadband noise attenuation. The ECLSS mufflers are currently scheduled to be installed on the Artemis II CM of the Orion spacecraft and will provide significant cabin comfort to crew during the mission.

Parametric modeling of steady-state gradient coil vibration: Resonance dynamics under variations in cylinder geometry

Gradient coil (GC) vibration is the root cause of many problems in MRI adversely affecting scanner performance, image quality, and acoustic noise levels. A critical issue is that GC vibration will be significantly increased close to any GC mechanical resonances. It is well known that altering the dimensions of a GC fundamentally affects the mechanical resonances excited by the GC windings. The precise nature of the effects (i.e., how the resonances are affected) is however not well understood. The purpose of the present paper is to study how the mechanical resonances excited by closed whole-body Z-gradient coils are affected by variations in cylinder geometry. A mathematical Z-gradient coil vibration model recently developed and validated by the authors is used to theoretically study the resonance dynamics under variation(s) in cylinder: (i) length, (ii) mean radius, and (iii) radial thickness. The forced-vibration response to Lorentz-force excitation is in each case analyzed in terms of the frequency response of the GC cylinder's displacement. In cases (i) and (ii), the qualitative dynamics are simple: reducing the cylinder length and/or mean radius causes all mechanical resonances to shift to higher frequencies. In case (iii), the qualitative dynamics are much more complicated with different resonances shifting in different directions and additional dependencies on the cylinder length. The more detailed dynamics are intricate owing to the fact that resonances shift at comparatively different rates and this leads to several novel and theoretically interesting predicted effects. Knowledge of these effects advance our understanding of the basic mechanics of GC vibration and offer practically useful insights into how such vibration may be passively reduced.

CHARACTERISTICS OF MICROSEISMS AND ACOUSTIC NOISES IN THE TRANSPORT POLYGON CONDITIONS

The work is related to numerical estimation and comparative analysis of microseismic and acoustic noise levels in transport polygon conditions. The aim of the work is to study and further define the difference between the signal and noise to improve the ability to detect poorly distinguishable events, as well as to study the propagation features of the interrelated seismic and acoustic wave fields. It is related to the fact that wave processes generated by many natural and anthropogenic sources are conjugate nature. In particular, it is related to simultaneous propagation of seismic waves in the ground and acoustic waves in the atmosphere. It determines expediency of taking into account simultaneously parameters of both types of waves in the tasks of geophysical monitoring of the environment, as well as in solving some applied problems of seismics and acoustics.

Double-Containment Coil With Enhanced Winding Mounting for Transcranial Magnetic Stimulation With Reduced Acoustic Noise.

This work aims to reduce the acoustic noise level of transcranial magnetic stimulation (TMS) coils. TMS requires high currents (several thousand amperes) to be pulsed through the coil, which generates a loud acoustic impulse whose peak sound pressure level (SPL) can exceed 130dB(Z). This sound poses a risk to hearing and elicits unwanted neural activation of auditory brain circuits. We propose a new double-containment coil with enhanced winding mounting (DCC), which utilizes acoustic impedance mismatch to contain and dissipate the impulsive sound within an air-tight outer casing. The coil winding is potted into a rigid block, which is mounted to the outer casing through the block´s acoustic nodes that are subject to minimum vibration during the pulse. The rest of the winding block is isolated from the casing by an air gap, and the sound is absorbed by polyester fiber panels within the casing. The casing thickness under the winding center is minimized to maximize the electric field output. Compared to commercial figure-of-eight TMS coils, the DCC prototype has 18-41dB(Z) lower peak SPL at matched stimulation strength, whilst providing 28% higher maximum stimulation strength than equally focal coils. The DCC design greatly reduces the acoustic noise of TMS while increasing the achievable stimulation strength. The acoustic noise reduction from our coil design is comparable to that provided by typical hearing protection devices. This coil design approach can enhance hearing safety and reduce auditory co-activations in the brain and other detrimental effects of TMS sound.

Acoustic Noise in Moscow during the Covid-19 Quarantine Period in 2020

This paper addresses the results of instrumental observation of acoustic oscillations in the atmosphere above the city of Moscow during the COVID-19 quarantine period. Instrumental observations made by the Geophysical Monitoring Center (GMC) at the Institute of Geosphere Dynamics (IGD), Russian Academy of Sciences, show that the quarantine-related decrease in production activity caused significant changes in the amplitude and spectral characteristics of acoustic noise above the city, as compared to the long-term averages. During the quarantine period, the amplitude of the main spectral components and the average amplitude of acoustic noise decreased by more than two times. The diurnal variation of the amplitude of noise caused by production activities in the daytime was much less evident. Our findings can be useful in determining the characteristics of technogenic noise sources and assessing its contribution to the total acoustic noise level of the city.

Contactless diagnostics of the technical state of the valve mechanism of the internal combustion engine

The aim of the study is to analyze the possibilities of developing a contactless diagnostics system of the technical state of the valve mechanism, which excludes mounting sensors on the body of the diagnosed equipment, by using a directional microphone as a sensitive element. In order to test the proposed hypothesis, a directional microphone designed to measure the level of acoustic noise, sound pressure level and to obtain amplitude-frequency characteristics in the range of 10-10 kHz has been used. In the work, an experimental determination of the spectrum of the valve mechanism acoustic vibration and its comparison with the spectrum obtained from an accelerometer has been carried out; the principle of building an automated diagnostic system using a directional microphone has been formulated.

Determination of the level of condensate by recording the noise level in the respiratory circuit of mechanical ventilation devices

Abstract. The method of determining the accumulation of condensate by registering the noise level in the respiratory circuit of ventilators is substantiated. According to the proposed method, the condition and performance of the apparatus is monitored during artificial lung ventilation and oxygen therapy. With hardware ventilation, an increasing turbulent flow of a water or gas stream is formed in the respiratory circuit, accompanied by an increase in the noise effect and vibration. An increase in the level of acoustic noise from fluctuations in the accumulation of condensate in gaseous media was recorded by an instrument for objective measurement of sound level a sound level meter. Indicators of noise effects reached a higher level on the wet circuit (the presence of condensation droplets or accumulations of mucus) of the liquid compared with the indicators obtained on the dry breathing circuit. The difference in recorded noise levels reached 10 dB, and increased from 37,73 to 47,36 dB. Areas of the respiratory circuit with the greatest degree of narrowing of the lumen and critical accumulations of water condensate and mucus are a source of turbulence in the air flow and increased noise. In conditions of prolonged artificial ventilation of the lungs, the rate of humidified air-gas flow is constantly changing, especially with hardware modeling of the phases of inspiration and expiration, and an increase in temperature in the humidifier chamber. The proposed technique is designed to identify critical levels of water condensate in the apparatus breathing circuits by recording the intensity of the increase in noise level and choosing the rational mode of operation of medical equipment. Data on the emerging critical situation are displayed on the sound level meter screen and inform medical personnel about the need to rehabilitate the circuit of the artificial lung ventilation apparatus. The primary field of application is resuscitation and intensive care units, medical transport teams during in-hospital or inter-hospital transportation, and surgical operating rooms during inhalation anesthesia.

Influence of the ray elevation angle on seafloor positioning precision in the context of acoustic ray tracing algorithm

In high precision underwater acoustic positioning, the ray tracing algorithm is often used to reduce the acoustic ray error. However, it is generally assumed that precision of the acoustic ray with low elevation angle is the same to that with high elevation angle. In the context of the ray tracing algorithm, with the Snell acoustic equation we derive a relationship between the ray tracing error and the observational elevation angle, and then a stochastic model of acoustic positioning is established referring to this relation. Experimental results show that the acoustic observation noise level is highly related to the elevation angle. This indicates that, the weight of observation with low elevation angle should be reduced in the seafloor positioning, and the proposed model can be used to reduce the influence of low elevation angle observations on the positioning accuracy.

Ergonomic Impact of Multi-rotor Unmanned Aerial Vehicle Noise in Warehouse Environments

Small multi-rotor unmanned aerial vehicles (UAVs) are poised to revolutionize commercial and logistics sectors through their versatility, maneuverability, and rapidly increasing sophistication and decreasing costs. However, these robotic systems also produce a substantial and overpowering level of acoustic noise that can potentially distract or harm humans who are working in close proximity to these UAVs. The aim of this study is to investigate the acoustic signature of quadcopter UAVs under various operating conditions, and its impact on human communication and psychological well-being. A unique design of experiments is developed allowing efficient usage of space and reducing the number of sessions required to complete the experiment. The human study has been conducted with popular UAV platforms in a workshop environment. Participants completed various listening tasks and their scores were compared with the noise signature of the UAV to identify operating factors with significant impact on human hearing and perceived annoyance.

Pointwise encoding time reduction with radial acquisition in subtraction-based magnetic resonance angiography to assess saccular unruptured intracranial aneurysms at 3Tesla.

To investigate the clinical utility of pointwise encoding time reduction with radial acquisition in subtraction-based magnetic resonance angiography (PETRA-MRA) and time-of-flight magnetic resonance angiography (TOF-MRA) to evaluate saccular unruptured intracranial aneurysms (UIAs). A total of 49 patients with 54 TOF-MRA-identified saccular UIAs were enrolled. The morphologic parameters, contrast-to-noise-ratios (CNRs), and sharpness of aneurysms were measured using PETRA-MRA and TOF-MRA. Two radiologists independently evaluated subjective image scores, focusing on aneurysm signal homogeneities and sharpness depictions using a 4-point scale: 4, excellent; 3, good; 2, poor; 1, not assessable. PETRA-MRA and TOF-MRA acoustic noises were measured. All aneurysms were detected with PETRA-MRA. The morphologic parameters of 15 patients evaluated with PETRA-MRA were more closely correlated with those receiving computed tomography angiography over those receiving TOF-MRA. No significant differences between PETRA-MRA and TOF-MRA parameters were seen in the 54 UIAs (p > 0.10), excluding those with inflow angles (p < 0.05). In four patients with inflow angles on PETRA-MRA, the angles were more closely related to those of digital subtraction angiography than those of TOF-MRA. CNRs between TOF-MRA and PETRA-MRA were comparable (p = 0.068), and PETRA-MRA sharpness values and subjective image scores were significantly higher than those of TOF-MRA (p < 0.001). Inter-observer agreements were excellent for both PETRA-MRA and TOF-MRA (intraclass correlation coefficients were 0.90 and 0.97, respectively). The acoustic noise levels of PETRA-MRA were much lower than those of TOF-MRA (59 vs.73dB, p < 0.01). PETRA-MRA, with better visualization of aneurysms and lower acoustic noise levels than TOF-MRA, showed a superior diagnostic performance for depicting saccular UIAs.

Selective suppression of amplitudes of frictional oscillations

Maintenance of sanitary codes and standards during operation of railway sorting sta-tions, in particular, standards which concern noise levels, is now the most pressing task. The analysis of noise has been carried out during operation of brake beams of car hump retarders with car wheelsets; the most problem frequency ranges have been revealed. On the basis of mod-elling bench tests with application of techniques of physical and mathematical modelling and tribospectral identification of friction processes we carried out selection of noise-suppressing cladding material which would reduce the level of acoustic noise at interaction of metal surfaces. Results of operational trials have confirmed efficiency of the chosen material in noise reduction.

Bus Passenger Transportation Quality Indicators: Organization of Instrumental Research of Additional Environmental and Sanitary Factors

The increase in vehicle-to-population ratio, in the number of personal cars and of individual travels defines extra requirements to the public transport service quality and safety within the public municipal passenger transport system. However, while specifying such requirements, the relevant regulations do not always consider the factors important for passenger service quality and driver work such as comfort and more general health and environmental standards. The purpose of the research is to identify additional factors that affect the city bus passenger service quality, to dev elop experimental test procedure and to conduct instrumental analysis of the transport service quality in accordance with the social standard as well as of additional parameters that influence it. The article presents the results of the following parameter measurements and sampling taken in the Moscow city buses: pollutants (hydrocarbons, formaldehyde, carbon (II) oxide and nitrogen dioxide) and artificial lighting (total illumination, lux, percent flicker, %), noise level, vibration, micro-climate. Based on measurements of harmful substances in the air of the bus passenger compartment, parameters of the micro-climate, artificial lighting, acoustic noise levels and general vibration, it was stated that they are within the limits of the permissible norms including those set by the European Union and WHO. Hence, the public transport service quality with reference to the proposed group of additional factors complies with standard requirements. It is proposed to extend the researches to other seasons as well as to other types of vehicles.