Noise Emission Levels Research Articles

Experimental investigation of the effect of roundabouts on noise emission level from motor vehicles

Roundabouts can provide benefits in many ways. They are safer, more efficient, less costly and more aesthetically appealing than standard at-grade intersections (controlled and signalized). The administrations have often identified roundabouts as a proven safety countermeasure for the following reasons: a) reduce overall conflict points and remove left-turn conflicts; b) reduce the vehicle speeds; and c) reduce accident severity for all users, allow safer merges into circulating traffic, and provide more time for all users to detect and correct their mistakes or the mistakes of others due to lower vehicle speeds. Also, from an operational point of view, roundabouts offer the following significant advantages: a) may reduce delays and queues than other forms of controlled intersections; b) can reduce lane requirements between intersections, including bridges between interchange ramp terminals; and c) create possibility for adjacent signals to operate with more efficient cycle lengths where the roundabout replaces a signal that is setting the controlling cycle length. Furthermore, roundabouts can provide important environmental benefits reducing delays and the number and duration of stops. Even in heavy traffic, vehicles keep moving in the queue rather than coming to a complete stop. This may reduce significantly noise and air quality impact as well as fuel consumption by reducing the number of acceleration/deceleration cycles and the time spent idling. In this article, the environmental aspects associated with roundabouts are treated with reference to issues related to noise production. The experimental investigation will refer to a heterogeneous succession of intersections (standard intersections, two-way stop-controlled and roundabouts) characterized by homogeneous traffic flows. The results of the research are interesting and contribute to consolidate the awareness, already highlighted by other international studies, of the role of roundabouts as effective measures to mitigate traffic noise. © 2019 Institute of Noise Control Engineering

Numerical modeling of aeroacoustic characteristics of different savonius blade profiles

Purpose This study aims to carry out numerical modeling to predict aerodynamic noise radiation from four different Savonius rotor blade profile. Design/methodology/approach Incompressible unsteady reynolds-averaged navier-stokes (URANS) approach using gamma–theta turbulence model is conducted to obtain the time accurate turbulent flow field. The Ffowcs Williams and Hawkings (FW-H) acoustic analogy formulation is used for noise predictions at optimal tip speed ratio (TSR). Findings The mean torque and power coefficients are compared with the experimental data and acceptable agreement is observed. The total and Mono+Dipole noise graphs are presented. A discrete tonal component at low frequencies in all graphs is attributed to the blade passing frequency at the given TSR. According to the noise prediction results, Bach type rotor has the lowest level of noise emission. The effect of TSR on the noise level from the Bach rotor is investigated. A direct relation between angular velocity and the noise emission is found. Practical implications The savonius rotor is a type of vertical axis wind turbines suited for mounting in the vicinity of residential areas. Also, wind turbines wherein operation are efficient sources of tonal and broadband noises and affect the inhabitable environment adversely. Therefore, the acoustic pollution assessment is essential for the installation of wind turbines in residential areas. Originality/value This study aims to investigate the radiated noise level of four common Savonius rotor blade profiles, namely, Bach type, Benesh type, semi-elliptic and conventional. As stated above, numbers of studies exploit the URANS method coupled with the FW-H analogy to predict the aeroacoustics behavior of wind turbines. Therefore, this approach is chosen in this research to deal with the aeroacoustics and aerodynamic calculation of the flow field around the aforementioned Savonius blade profiles. The effect of optimal TSR on the emitted noise and the contribution of thickness, loading and quadrupole sources are of interest in this study.

A Review on GIS-Based Approach for Road Traffic Noise Mapping

Objectives: Road traffic noise pollution is identified as one of the serious alarms that influence the attribute of the urban regions. This study highlights the different models used for noise mapping using GIS. Methods: Interpolation (krigging) method can be used to develop different noise contour maps. Noise emission levels are calculated from many sound propagation models like ISO 9613:1996, Calculation of Road Traffic Noise (CoRTN 88), Harmonoise Noise Prediction Algorithm and Nord 2000. Findings: In study of road traffic noise mapping, noise levels have been predicted using a specially developed noise computer models. The output results of the computer noise models can add as input data for a GIS. The interpolation methods available in GIS can develop noise contour maps. Application: This study highlights the different Geographic Information System techniques applied for the noise mapping. Keywords: Environmental Pollution, Geographical Information System, Noise Mapping, Propagation Models, Road Traffic Noise

Noise Impact Assessment of Thermal Plant Facilities on Receptor Environments

Noise pollution is considered as a serious environmental nuisance in the urban areas. This study has used the VDI code 2714 to investigate the impacts of the noise from all the power generation and ancilliary facilities in the proposed Independent Power Plant, Agbara, Ogun State receptor environment. Kriging interpolation method in SurferR 8.0 software to predict noise emission levels within the fence line of the proposed Independent Power Plant. Calculations of possible noise levels at some receptors locations around the plant were carried out using the VDI code 2714. Four operation scenarios were considered in this study. The scenarios considered include: Noise emission from power generation facilities only (Scenario 1); Noise from the use of Compressors and Transformers (Scenario 2); Noise emission from the operation of power generation and ancillary equipment (Scenario 3); and Noise emission from the use of Backup Generators (Scenario 4). The maximum noise from the four scenarios were 112.34, 114.58, 116.61 and 110.01 dB(A), respectively, which is above the 8-hour 90 dB(A) limit recommended by the Federal Ministry of Environment (FMEnv). The operation of the proposed power plant will not have significant impact on the receptor environments except for Karogbaji which receives less than 12 dB(A) for the worst-case scenario (Scenario 3). The modeling results show that the predicted noise levels generated by the proposed operation would generally be within the established noise criteria at all the receptor locations under all conditions.

Advanced low-noise aircraft configurations and their assessment: past, present, and future

Aircraft noise remains the key inhibitor of the growth of air transportation, but the focus of the noise mitigation strategies has changed. As the propulsor fan pressure ratio is decreased for improved fuel burn and lessened environmental impact, the propulsion system noise can be reduced near or even below the noise level of the airframe. Jet noise has become less of a concern, and during approach and landing, the acoustic signature is predominantly set by the airframe. Novel aircraft concepts and architectures, enabled by distributed, more integrated, and boundary-layer ingesting propulsion systems, pose new aeroacoustic problems which require innovative approaches and call for teaming and collaboration as the technological challenges cut across disciplines. One past example of such a collaborative research effort was the Silent Aircraft Initiative (SAI), aimed at the conceptual design of an aircraft imperceptible to the human ear outside the airport perimeter. The initiative brought together researchers from academia, industry, and government agencies. This chapter gives a brief summary of the Silent Aircraft Initiative, the SAX-40 aircraft design, and the noise reduction technologies which were pursued. A decade past SAI, novel aircraft architectures such as the D8 double bubble aircraft, the outcome of a joint effort between MIT, Aurora Flight Sciences and Pratt and Whitney, are being pursued in the quest of reducing the climate impact of aviation. With regulations continuing to reduce the allowable aviation noise emission levels, both new challenges and new opportunities are emerging. Electric, hybrid, and turbo-electric aircraft concepts are currently being investigated as potential game changers. Independent of the level of electrification, noise will remain a major issue as air transportation is growing and mobility might become a key driver. The chapter discusses a selection of enabling technologies and their implications on acoustics and noise and gives a perspective on future trends and new directions in aeroacoustics required to address the challenges.

Features of an Asynchronous Motor with a Double-Layer Rotor in Ship Pumping Equipment

This article examines the characteristics and structure an asynchronous motor with a double-layer rotor for ship electric pumping units, as well as approaches to studying it. The main technical requirement for such motors is a low level of noise emission when providing the required heat removal from the operating motor. The use of an external double-layer rotor in this motor makes it possible to significantly improve its working and maintenance characteristics.

Noise exposure hazard at supporting facilities of Dr. Soetomo General Hospital, Surabaya, Indonesia

Noise exposure in a hospital is known to have considerable impact not only to the healthy workers, but affects the ability for speedy recovery to the patients as well. However, recent investigations showed that the noise emission in a hospital tends to increase from year to year, for example John Hopkins Hospital. Dr. Soetomo General Hospital is the largest hospital in eastern part of Indonesia serving 2,500 outpatients and 1,500 inpatients per day as of January 2017, tripled from 2014. This also implies that the activities also increase significantly, from supporting services such as laundry to clinical services. In this paper, we present our recent study on the noise emission focusing on the supporting activities of the hospital such as water pump station, boiler, central kitchen, incinerator and workshop. The aim is to investigate the noise dose exposure to the workers of each supporting facility. We measured the noise emission level of the facility during its respective working hours. The results showed that all the facilities emitted higher level (in decibel) than allowed by the WHO. For the continuous noise, the average noise level for the water pump station was about 89.3 dB(A) and the workers were exposed almost 100 times more than that of the allowed noise exposure daily dose. The crushers at the incinerator facility were the highest of all intermittent noise sources at 98.4 dB(A). Furthermore, the noise level difference between outside and inside the water pump station was only reduced 1 dB, which suggests that either the sound enclosures was no longer effective. To summarize, the overall results showed that either the continuous or intermittent noise source the workers were exposed to high dose of noise daily.

Visualizing aviation impacts: Modeling current and future flight trajectories with publicly available flight data

As the demand for air travel continues to grow both nationally and internationally, airports seek airfield expansions and new infrastructure to accommodate new aircraft movements. However, airport expansion initiatives – runway extensions and/or new runway construction – directly impact terminal airspace operations. A change in flight paths near the airport affects the population living proximate to the airport, increasing noise levels and exposure to pollutants emitted by low-altitude departures and arrivals. While airspace procedures and their impacts are well-understood by aviation stakeholders, they are often convoluted and technical in nature. To this end, we propose a methodology to visualize terminal airspace trajectories leveraging publicly available data and commonly-used software. The trajectories are extracted via polynomial regression and hyperbolic tangent interpolation is applied to reflect accurate final approach maneuvers. Final visualizations are rendered in ArcGIS, a geographic information system used by many Metropolitan Planning Organizations. These trajectory visualization modules can also be combined with external models that provide noise contour projections and emission level estimations. We present a case study of Chicago O’Hare International Airport (ORD) due to the contentious O’Hare Modernization Program. The resultant interactive and dynamic three-dimensional trajectory airspace maps for ORD rendered via ArcGIS are easy to understand and customize, allowing MPOs to package them into downloadable online modules. MPOs armed with these modules will bridge the critical gap between the technical knowledge presented by authorities touting airport expansions and the residents who are impacted by the expansions.

Diagnosis of the noise emission in a plastic recycling plant located in the municipality of Caçador, Santa Catarina, Brazil

Background: With industrial development, many production processes emit high levels of noise, presenting problems for society. This emission causes an environmental impact on employees and also on the surrounding environment. Materials and Methods: The present study was performed with the objective of analyzing the noise emission in a plastic recycling plant in the municipality of Cacador, Santa Catarina (SC), Brazil, with the perspective of the environmental suitability with the regulatory environmental agencies. Results: According to the relevant legislation, the plant had significant noise emission levels, reaching 98 A-weighted decibels dB (A), since NBR 10151/2000has permitted the emission of 70 dB (A) for industrial areas. Conclusions: Thus, the plant under study needs to seek for ways to reduce its noise emission in its production process; this issue can be attributed to the isolation of the washing process, as the centrifuges in this process are responsible for generation of main part of the noise. Regarding the occupational hygiene process, the plant needs the distribution of ear protectors due to the emission of noise, seeking the best quality of work for its employees.

Determination of environmental noise levels at central Balikesir hospitals

In this study, our goal was to determine of noise sources and emission levels from very sensitive environments, such as hospitals, at downtown of Balikesir. It was also aimed to create noise pollution maps as the first time for those full-scale hospitals in Balikesir by carrying out of this study. According to the study results, it was determined that the noise level in Balikesir State Hospital (BSH), where is located closer to the city center, was higher than the noise levels in Atatürk State Hospital (ASH). In conclusion, the predicted noise values at BSH were higher about 9% (or approximately 7dBa) than the actual measured values. The modeling process was not performed at ASH, due to noise levels of ASH did not exceed the legal limits.

At-ear noise levels under the helmet: a field study on noise exposure of young motorcyclists

At-ear noise exposure assessments of motorcyclists, with the function of speed, would be unsafe as on-road data acquisition has certain constraints including the operations and portability of appropriate instrument. Currently, there are no standardized protocols and methods for measuring the noise under motorcycle helmets. Furthermore, standard permissible noise emission levels for commuter motorcyclists are also not defined. Therefore, this study was aimed to investigate the motorcycle noise exposure assessments in realistic environment among young riders. A personal dosimeter was utilized to calculate the daily noise exposure level (L Aeq , 8h) under three different standards including: OSHA-HC (Occupational Safety and Health Administration, Hearing Conservation), OSHA-PEL (Permissible Emission Level) and ACGIH/NIOSH (American Conference of Governmental Industrial Hygienists/ National Institute of Occupational Safety and Health). The study design consisted of noise assessment of riders (age range:19 to 25 years) at-ear under the open-face helmet in-realistic situation (main road to the motorway) motorcycling in dry weather conditions. Personal dosimeter results ( n =52) revealed the average noise exposure level of 93.64 dBA, 92.51 dBA, 95.29 dBA for OSHA-HC, OSHA-PEL and ACGIH/NIOSH respectively. The mean Time-Weighted Average (TWA) was 76.82 dBA, 75.69 dBA, 85.16 dBA for OSHAHC, OSHA-PEL and ACGIH/NIOSH respectively. Under the ACGIH and NIOSH standard, the TWA for motorcyclists is at hazardous limits, which requires further investigations associated with health effects on riders. Standardized methods and configurations should be set for assessing noise exposure related to the motorcycling. Keywords: Motorcycle noise, Wind noise, Dosimeter, OSHA, ACGIH

Experimental Investigation of Cycle Properties, Noise, and Air Pollutant Emissions of an APS3200 Auxiliary Power Unit

Auxiliary power unit (APU) operators face increasingly stricter airport requirements concerning exhaust gas and noise emission levels. To simultaneously reduce exhaust gas and noise emissions and to satisfy the increasing demand of electric power on board, optimization of the current technology is necessary. Prior to any possible demonstration of optimization potential, detailed data of thermodynamic properties and emissions have to be determined. Therefore, the investigations presented in this paper were conducted at a full-scale APU of an operational aircraft. A Pratt & Whitney (East Hartford, CT) APS3200, commonly installed in the Airbus A320 aircraft family, was used for measurements of the reference data. In order to describe the APS3200, the full spectrum of feasible power load and bleed air mass flow combinations were adjusted during the study. Their effect on different thermodynamic and performance properties, such as exhaust gas temperature, pressure as well as electric and overall efficiency is described. Furthermore, the mass flows of the inlet air, exhaust gas, and fuel input were determined. Additionally, the work reports the exhaust gas emissions regarding the species CO2, CO, and NOx as a function of load point. Moreover, the acoustic noise emissions are presented and discussed. With the provided data, the paper serves as a database for validating numerical simulations and provides a baseline for current APU technology.

Experimental and Stochastic Reactor Modeling Results of an HCCI Engine Fueled with Primary Reference Fuel

In recent years, much research has been performed in order to decrease fuel consumption, noise, and exhaust emission levels in internal combustion engines. In this study, the effects of excess air coefficient on performance and exhaust emissions (CO, CO2) of an HCCI engine fueled with primary reference fuel (PRF) were investigated for different intake air pressure and temperature values. The simulation studies were performed by using SRM Suite software. The chemical kinetic mechanism, which contains 138 species and 633 reactions that are embedded into the program, was used to simulate the combustion of the PRF fuel during the combustion simulations. The analysis covers the full cycle and provides data about induction, compression, combustion, expansion, and exhaust. The exhaust emissions, cylinder pressure, and heat release rate results were compared with the experimental data. The zero-dimensional software (SRM Suite) gives quite reasonable results compared with the experimental data, and it has advantag...

Energy Efficient and Environmentally Friendly Hybrid Conversion of Inland Passenger Vessel

Abstract The development and growing availability of modern technologies, along with more and more severe environment protection standards which frequently take a form of legal regulations, are the reason why attempts are made to find a quiet and economical propulsion system not only for newly built watercraft units, but also for modernised ones. Correct selection of the propulsion and supply system for a given vessel affects significantly not only the energy efficiency of the propulsions system but also the environment - as this selection is crucial for the noise and exhaust emission levels. The paper presents results of experimental examination of ship power demand performed on a historic passenger ship of 25 m in length. Two variants, referred to as serial and parallel hybrid propulsion systems, were examined with respect to the maximum length of the single-day route covered by the ship. The recorded power demands and environmental impact were compared with those characteristic for the already installed conventional propulsion system. Taking into account a high safety level expected to be ensured on a passenger ship, the serial hybrid system was based on two electric motors working in parallel and supplied from two separate sets of batteries. This solution ensures higher reliability, along with relatively high energy efficiency. The results of the performed examination have revealed that the serial propulsion system is the least harmful to the environment, but its investment cost is the highest. In this context, the optimum solution for the ship owner seems to be a parallel hybrid system of diesel-electric type

Perceived integrated impact of visual intrusion and noise of motorways: Influential factors and impact indicators

Motorways are often seen as intrusive to both landscape and soundscape, and recent studies on multisensory perception suggest that an integrated assessment of the environmental impacts is necessary. This paper investigates the effects of traffic condition, distance to road and background landscape on the perceived integrated impact of noise and visual intrusion of motorways, and explores if noise exposure can be a powerful indicator for the perceived integrated impact. Six traffic conditions, consisting of three levels of noise emission×two levels of heavy good vehicle percentage in traffic composition, two types of background landscape and three distances to road, were designed as experimental scenarios, and created using computer visualisation and edited audio recordings. A laboratory experiment was carried out to obtain ratings of perceived environmental quality of each experimental scenario. The results show that traffic volume as expressed by noise emission level strongly influenced the perceived integrated impact, whereas traffic composition did not make noticeable differences. Distance to road was the second most influential factor, followed by background landscape. A regression model using noise level at receiver position and type of background landscape as independent variables was developed and can explain about a quarter of the variation in the perceived integrated impact.

Acoustic and heat release signatures for swirl assisted distributed combustion

The acoustic signal and heat release fluctuations are examined from a swirl combustor using methane as the fuel. The focus was on flame stability and noise emission that have direct relevance in further developing distributed combustion for gas turbine applications and oxy-fuel combustion. Three regimes are examined in this paper, the first being a swirl mode at equivalence ratios between 0.9 and 0.55. The second one being distributed combustion, achieved through N2/CO2 dilution to reach oxygen concentration below 15%, fostering distributed reaction. The third was oxy-fuel flame using increased amounts of CO2 dilution to reach distributed reaction. For the first case, lowering the equivalence ratio led to a reduction in the peak sound pressure level around 500Hz and a decrease in heat release fluctuations. For all the equivalence ratios, close coupling between acoustic signature and heat release fluctuations existed around 200Hz. Distributed combustion, achieved at oxygen concentration below 15%, showed a much lower peak sound pressure levels at the 500Hz range with no coupling between heat release fluctuations and acoustic signal, outlining the flame stability at this regime. Also, the noise emission levels were significantly reduced under this mode. For the third regime, increase in CO2 dilution resulted in high heat release fluctuations and an unstable flame which oscillated between two different flame modes, a feature that did not exist in the first two regimes. Further increase in CO2 led to achieving distributed reaction and a much more stable flame as compared to its oscillatory behavior at lower CO2 amounts, along with reduced noise emission levels. This outlines the possibility of achieving distributed combustion in a stable manner via CO2 dilution in oxy-fuel flames.

Simulated Computation of the Acoustic Energy Transfer through the Structure of Porous Media in Application of Passenger Carriage Body

The paper deals with the reconstruction of the rail-way passenger carriage floor for the improvement of the sound reduction index. Reconstruction was performed by using new acoustic material with a fibrous microstructure. The paper propose materials compared with simulated calculation of the acoustic energy transfer trough the porous microstructure of fibrous material, and further monitoring of their final effect in different fields of application in the floor and body structure of railway passenger carriage. Environmental aspects of construction, operation and maintenance of vehicles shall become an important significance on a global scale in recent years. Rail noise reduction is current topic nowadays. Especially technical solutions in the construction of railway vehicles, railway track construction and technological aspects of railway operations can effectively reduce the noise emitted by railway vehicles. The level of noise emissions from railway vehicles are systematically reduced by TSI standards. Vehicle design is largely influenced by the properties of materials and structures. Currently, the theory of multi-layer separating structures is used in the vehicle design.

Minimizing vehicle noise passing the street bumps using Genetic Algorithm

The purpose of this paper is to optimize noise emission level associated with two types of speed reducers for different speeds of a vehicle (20, 40, 60km/h) by Genetic Algorithm and Artificial Neural Network. The optimization shows that the maximum level of noise is sensitive to speed reducer dimensions. It is reduced by 24dB(A) by changing the width from 0.6m to 0.3m for the height 0.04m whereas, it is reduced by 32dB(A) by changing from the height 0.055m and the width 0.9m to the height 0.04m and the width 0.3m.

Experimental investigation of the effect of speed bumps in sequence on noise emission level from motor vehicles

It is known that speed bumps are devices capable of reducing the speed of vehicles (traffic calming measures). Bumps arranged in sequence are capable of inducing a speed regime almost constant along the road sections in which they are installed. However, the impact of vehicles on the bumps generates noise that is annoying to residents. Many studies in the literature have estimated the production of noise due to the transit of vehicles over isolated speed bumps. Less investigated, however, is the phenomenon of the noise production on the speed bumps arranged in a sequence. In this paper, the authors analyze the effects of speed bumps arranged in a sequence on the production of noise. In order to do this, two urban road sections are selected with several speed bumps placed sequentially. The survey was carried out experimentally using three vehicles (a low-powered car, a high-powered car and a motorcycle). The authors, using sound level meters data, assessed the sound levels produced by these vehicles, considering the conditionings on the dynamics of motion induced by the sequence of bumps.

Video dosimetry as a method to reduce noise induced hearing loss

Risk perception plays an important role in a person's decision to wear hearing protection to reduce the occurrence of noise induced hearing loss. Therefore, as part of the safety training for a worksite, it is important to educate workers about the potential sources of noise exposure at the worksite so that the workers are aware of the risk. However, teaching a workforce with a range of educational and language skill levels about the risk of noise at the workplace can be a challenge. Instructing people that sources of noise such as machinery are loud may not effectively communicate to people that they could be exposed to noise which is loud enough to damage their hearing. Furthermore, not all of the sources of noise at the worksite may be known or included in the safety training, potentially leading the workers to believe that they are not exposed to high noise emission levels when they actually are at the worksite. This paper describes a measurement method called video dosimetry which combines images taken with a wearable camera with sound pressure levels measured using a dosimeter to create first person videos. The videos show the actions the person wearing the camera was engaged in at the worksite and the corresponding exposure levels. This information can help safety advisors to identify the noise exposure risk while engaged in common actions at the worksite. Furthermore, the videos based on first person images represent an engaging tool for educating at risk workers about the noise exposure levels associated with common activities occurring in the worksite.