Environmental Noise Reduction Research Articles

Study on sound absorption properties of fiber materials and perforated components and their composite structures with different structural parameters

Fiber materials and perforated components are often used as basic structural units, which are widely used in the field of environmental noise reduction and automotive noise reduction.In this work, the effects of different structural parameters on the sound absorption properties of fiber materials, perforated components and their composite structures are studied. The sound absorption coefficients of fiber materials, perforated elements and their composite structures with different structural parameters were simulated by COMSOL finite element software. The transfer function method is used to measure the sound absorption in the impedance tube. The simulation results are in good agreement with the experimental results. The results show that the thickness of sound absorption material has a great influence on the sound absorption coefficient. The perforation rate is an important factor affecting the sound absorption performance of perforated components. When the perforation rate is high, it hardly absorbs sound. With the increase of aperture and wall thickness, the sound absorption performance increases in low frequency band and decreases in medium and high frequency bands. The non-periodic oscillation of sound absorption coefficient occurs with the change of cavity thickness.

Design and Implementation of an Active Noise Control Headphone With Directional Hear-Through Capability

This article presents the design and implementation of an active noise control (ANC) headphone system with a directional hear-through capability and compares the performance of this system to that of a standard hear-through headphone system. The directional hear-through ANC headphones are a novel integration of microphone array beamforming and ANC technologies into a pair of headphones, which provide the consumer with additional functionality and new, digitally augmented ways to interact with their acoustic environment. As the microphone array is necessarily compact, superdirective beamforming is utilised to increase its low and mid frequency directional performance. In this unique integration of two current consumer technologies, first, the ANC subsystem attempts to maximise the attenuation and then the beamformer output is added to the control signal and reproduced by the headphones’ loudspeakers, with the appropriate compensation to avoid self-cancellation. The experimental study demonstrates that the proposed spatially selective ANC headphones provide a hear-through capability in the look direction, whilst reducing ambient noise and enabling the wearer to experience reduced noise communication in a noisy environment. The proposed system thus offers the consumer the potential for an electronically enhanced acoustic experience, allowing a selective reduction in environmental noise whilst desired exterior noise remains audible.

Reduction of Environmental Magnetic Field Noise for Detection of Small Magnetic Contaminants

When performing high-sensitivity magnetic measurements via a high-sensitivity magnetic sensor such as a SQUID (Superconducting QUantum Interference Device) magnetometer, it is necessary to shield from environmental magnetic noise by employing a magnetic shield box. In general, however, the low frequency of such noise decreases the shielding performance of the magnetic shield box. Hence, the magnetic metallic contaminant signal and the low-frequency ambient magnetic field noise overlap, which makes filtering a challenging task. Therefore, we studied a system that suppresses gradient magnetic noise such as low-frequency environmental noise superimposed on a contaminant signal and commercial power supply noise localized spatially.

A Minimum Rank Approach for Reduction of Environmental Noise in Near-Field Array Antenna Diagnosis.

A method to filter out the contribution of interference sources in array diagnosis is proposed. The interference-affected near field measured on a surface is treated as a (complex-data) image. This allows to use some modern image processing algorithms. In particular, two strategies widely used in image processing are applied. The first one is the reduction of the amount of information by acquiring only the innovation part of an image, as currently happens in video processing. More specifically, a differential measurement technique is used to formulate the estimation of the array excitations as a sparse recovery problem. The second technique has been recently proposed in video denoising, where the image is split into a low-rank and high-rank part. In particular, in this paper the interference field is filtered out using sparsity as discriminant adopting a mixed minimum norm and trace norm minimization algorithm. The methodology can be applied to both near and far field measurement ranges. It could be an alternative to the systematic use of anechoic chambers for antenna array testing.

Preparation and Characterization of Gradient Compressed Porous Metal for High-Efficiency and Thin-Thickness Acoustic Absorber.

Increasing absorption efficiency and decreasing total thickness of the acoustic absorber is favorable to promote its practical application. Four compressed porous metals with compression ratios of 0%, 30%, 60%, and 90% were prepared to assemble the four-layer gradient compressed porous metals, which aimed to develop the acoustic absorber with high-efficiency and thin thickness. Through deriving structural parameters of thickness, porosity, and static flow resistivity for the compressed porous metals, theoretical models of sound absorption coefficients of the gradient compressed porous metals were constructed through transfer matrix method according to the Johnson–Champoux–Allard model. Sound absorption coefficients of four-layer gradient compressed porous metals with the different permutations were theoretically analyzed and experimentally measured, and the optimal average sound absorption coefficient of 60.33% in 100–6000 Hz was obtained with the total thickness of 11 mm. Sound absorption coefficients of the optimal gradient compressed porous metal were further compared with those of the simple superposed compressed porous metal, which proved that the former could obtain higher absorption efficiency with thinner thickness and fewer materials. These phenomena were explored by morphology characterizations. The developed high-efficiency and thin-thickness acoustic absorber of gradient compressed porous metal can be applied in acoustic environmental detection and industrial noise reduction.

Low Frequency Sound Absorption by Optimal Combination Structure of Porous Metal and Microperforated Panel

The combination structure of a porous metal and microperforated panel was optimized to develop a low frequency sound absorber. Theoretical models were constructed by the transfer matrix method based on the Johnson—Champoux—Allard model and Maa’s theory. Parameter optimizations of the sound absorbers were conducted by Cuckoo search algorithm. The sound absorption coefficients of the combination structures were verified by finite element simulation and validated by standing wave tube measurement. The experimental data was consistent with the theoretical and simulation data, which proved the efficiency, reliability, and accuracy of the constructed theoretical sound absorption model and finite element model. The actual average sound absorption coefficient of the microperforated panel + cavity + porous metal + cavity sound absorber in the 100–1800 Hz range reached 62.9615% and 73.5923%, respectively, when the limited total thickness was 30 mm and 50 mm. The excellent low frequency sound absorbers obtained can be used in the fields of acoustic environmental protection and industrial noise reduction.

Quantitative Independent Component Selection Using Attractor Analysis for Noise Reduction in Magnetocardiogram Signals

We studied a method for reduction of environmental magnetic noise in magnetocardiograms using independent component analysis, which is a useful technique to separate signal from noise. However, this separation usually relies on subjective choices of the independent components to reconstruct the signal. Hence, we propose a method for quantitative component selection using attractor analysis and coefficient of multiple determination. We verified the noise reduction accuracy using low signal-to-noise ratio experimental data (0 and −10 dB). First, a threshold derived from the coefficient of multiple determination was determined from the results for independent component selection. Then, noise reduction accuracy was evaluated from the spatial correlation coefficients obtained using the proposed method. The results show a considerable reduction of noise for a threshold of 0.6, with its accuracy being almost equal to the maximum noise reduction accuracy obtained from the best selection pattern.

Open windows for natural airflow and environmental noise reduction

ABSTRACTFor buildings in tropical climates, the use of open windows for natural ventilation can not only provide low cost and low energy comfort but also provide thermal delight for occupants. However open windows let in environmental noise. The size and location of windows in walls are key but this study set out to determine whether there are any window forms that can effectively reduce the level of sound ingress into a building. A top-hung window was chosen for this study looking at the dimensions of the window opening and its orientation in relation to the environmental noise source. The top-hung form was selected for its potential to balance the functions of allowing airflow while potentially blocking and reducing noise levels with its window pane angle. The window pane was tested in a laboratory at three opening angles: 0° (closed), 5°, and 10° to let the outdoor air in. The angles were also tested in three different orientations in relation to the noise source position: perpendicular, sideways 60°, and sideways 90°. The test was conducted at 1/3 octave band frequency as specified by ASTM E90-09 to obtain the transmission loss, then ASTM E1332-90 was referred to calculate the outdoor-indoor transmission class (OITC) of the specimens. The study revealed that window orientation and extent of the openings and window pane angle have little effect on noise reduction. The paper concludes with a discussion of how higher levels of natural ventilation can be achieved, particularly in noisy urban areas. The top-hung window, once open, barely blocks environmental noise. However, when the window was closed, the perpendicular orientation offered more noise reduction when compared windows placed sideways to the noise source. The adjustable pane-angle of a top-hung window placed perpendicular to the airflow, and thus the noise source, seemed to have the most potential to balance the functions of allowing airflow when opened and reducing significant noise when closed. Nonetheless, an open window that through its design alone can significantly reduce the ingress of ambient noise into a building is still an issue.

NewsCAP: Environmental noise reduction can improve health

NewsCAP: Environmental noise reduction can improve health

Magnetoencephalogram recording during simulated driving: Towards an ecologically-valid paradigm

Magnetoencephalogram recording during simulated driving: Towards an ecologically-valid paradigm

A Study on the Device Installed on the Barrier for The Environmental Noise Reduction in 400 km/h High Speed Railway

A Study on the Device Installed on the Barrier for The Environmental Noise Reduction in 400 km/h High Speed Railway

Reduction in environmental noise by a novel nanocomposite, containing cellulose, polyvinyl acetate, and aluminum oxide nanoparticles

The aim was to evaluate sound adsorption coefficient, sound transmission loss, mechanical properties, and physical characteristics of a novel nanocomposite, containing cellulose fiber (CF), polyvinyl acetate (PVA), and aluminum oxide nanoparticles (AO NPs). To prepare CF/PVA/AO NP nanocomposites, 100 g CF and 200 g PVA were hardly mixed, and then, AO NP at different contents was added, including 1–4%. The sound absorption coefficient and transmission loss were measured by acoustic tube at four frequencies, including 250, 500, 1000, and 2000 Hz. In the next step, density and water absorption were measured. Also, Young’s modulus, tensile strength, and strain to failure were recorded by extensometer. This study showed that the increase in AO NPs led to increase in sound adsorption coefficient, water adsorption, tensile strength, Young’s modulus, and fracture strain. Moreover, the increase in AO NPs led to decrease in sound transmission loss and density. The authors propose that CF/PVA/AO NPs (4%) nanocomposite is suitable to reduce noise from environment at frequency of 250–2000 Hz.

Environmental noise levels in 2 intensive care units in a tertiary care centre

The World Health Organisation (WHO) has established a maximum noise level of 40 decibels (dB) for an intensive care unit. The aim of this study was to compare the noise levels in 2 different intensive care units at a tertiary care centre. Using a cross-sectional design study, an analysis was made of the maximum noise level was within the intensive coronary care unit and intensive care unit using a digital meter. A measurement was made in 4 different points of each room, with 5minute intervals, for a period of 60minutes 7:30, 14:30, and 20:30. The means of the observations were compared with descriptive statistics and Mann-Whitney U. An analysis with Kruskal-Wallis test was performed to the mean noise level. The noise observed in the intensive care unit had a mean of 64.77±3.33dB (P=.08), which was similar to that in the intensive coronary care unit, with a mean of 60.20±1.58dB (P=.129). Around 25% or more of the measurements exceeded the level recommended by the WHO by up to 20 points. Noise levels measured in intensive care wards exceed the maximum recommended level for a hospital. It is necessary to design and implement actions for greater participation of health personnel in the reduction of environmental noise.

A demand-side approach to the optimal deployment of electric vehicle charging stations in metropolitan areas

Despite all the acknowledged advantages in terms of environmental impact reduction, energy efficiency and noise reduction, the electric mobility market is below expectations. In fact, electric vehicles have limitations that pose several important challenges for achieving a sustainable mobility system: among them, the availability of an adequate charging infrastructure is recognized as a fundamental requirement and appropriate approaches to optimize public and private investments in this field are to be delineated. In this paper we consider actual data on conventional private vehicle usage in the urban area of Rome to carry out a strategy for the optimal allocation of charging infrastructures into portions (subareas) of the urban area, based on an analysis of a driver sample under the assumption of a complete switch to an equivalent fleet of electric vehicles. Moreover, the energy requirement for each one of the subareas is estimated in terms of the electric energy used by the equivalent fleet of electric vehicles to reach their destination. The model can be easily generalized to other problems regarding facility allocation based on user demand.

Opportunities for Environmental Noise Mapping in Saudi Arabia: A Case of Traffic Noise Annoyance in an Urban Area in Jeddah City.

As the traffic and other environmental noise generating activities are growing in The Kingdom of Saudi Arabia (KSA), adverse health and other impacts are expected to develop. The management of such problem involves many actions, of which noise mapping has been proven to be a helpful approach. The objective of the current study was to test the adequacy of the available data in KSA municipalities for generating urban noise maps and to verify the applicability of available environmental noise mapping and noise annoyance models for KSA. Therefore, noise maps were produced for Al-Fayha District in Jeddah City, KSA using commercially available noise mapping software and applying the French national computation method “NMPB” for traffic noise. Most of the data required for traffic noise prediction and annoyance analysis were available, either in the Municipality GIS department or in other governmental authorities. The predicted noise levels during the three time periods, i.e., daytime, evening, and nighttime, were found higher than the maximum recommended levels established in KSA environmental noise standards. Annoyance analysis revealed that high percentages of the District inhabitants were highly annoyed, depending on the type of planning zone and period of interest. These results reflect the urgent need to consider environmental noise reduction in KSA national plans. The accuracy of the predicted noise levels and the availability of most of the necessary data should encourage further studies on the use of noise mapping as part of noise reduction plans.

Background Music Playback in the Preoperative Setting: Does It Reduce the Level of Preoperative Anxiety Among Candidates for Elective Surgery?

Contemporary medicine and nursing use music to stabilize mood, relieve tension and anxiety, and achieve higher treatment efficiency. Preoperative anxiety may be responsible for cognitive and behavioral changes affecting treatment efficiency. To evaluate the effect of background music on preoperative anxiety in elective surgery patients and on noise levels in the surgery waiting room. One hundred fifty-nine elective surgery patients were divided into an intervention group (n = 82) and a control group (n = 77). Data were collected and evaluated on the evening before surgery in the department, on entering the waiting room, and 30minutes later in the preoperative setting. Data were gathered using the State-Trait Anxiety Inventory scale and by measuring vital signs. Daily noise levels in the preoperative waiting room were recorded as well. Exposure to background music was associated with decreased levels of state anxiety irrespective of age, sex, and previous exposure to surgery or anesthesia (P < .001). Background music was also related to environmental noise reduction in the surgery waiting room (P < .0001). Background music can be useful as a means of decreasing preoperative anxiety.

Investigation of a Jet-Noise-Shielding Methodology

Ongoing research toward the reduction of environmental noise from aircraft is investigating the possible shielding of engine-noise sources by novel airframe configurations. To assess the noise-reduction benefits attainable from such configurations, it is necessary to develop appropriate acoustic evaluation tools. In this paper, a jet-noise-shielding-prediction methodology is described. The Tam–Auriault (“Jet Mixing Noise from Fine-Scale Turbulence,” AIAA Journal, Vol. 37, No. 2, 1999, pp. 145–153) jet-noise model with a Reynolds-averaged Navier–Stokes solution input, together with a Fresnel–Kirchhoff diffraction method (Fundamentals of Physical Acoustics, Wiley-Interscience, New York, 2000, pp. 472–494), is used to make isolated and shielded far-field jet-noise predictions. This methodology is employed as a sensitivity-analysis tool to establish the relative importance of the source location, spatial extent, and directivity in jet-noise-shielding predictions. Predictions have been made for a shielded single-stream Mach 0.9 jet, and compared with experimental data. Good qualitative agreement is observed, and the disagreement in the shielding levels is most likely due to underestimation of the source axial extent by the jet-noise model.

Cerebral Perfusion Pressure and Intracranial Pressure in Traumatic Brain Injury

Nearly 300,000 children and adults are hospitalized annually with traumatic brain injury (TBI) and monitored for many vital signs, including intracranial pressure (ICP) and cerebral perfusion pressure (CPP). Nurses use these monitored values to infer the risk of secondary brain injury. The purpose of this chapter is to review nursing research on the monitoring of ICP and CPP in TBI. In this context, nursing research is defined as the research conducted by nurse investigators or research about the variables ICP and CPP that pertains to the nursing care of the TBI patient, adult or child. A modified systematic review of the literature indicated that, except for sharp head rotation and prone positioning, there are no body positions or nursing activities that uniformly or nearly uniformly result in clinically relevant ICP increase or decrease. In the smaller number of studies in which CPP is also measured, there are few changes in CPP since arterial blood pressure generally increases along with ICP. Considerable individual variation occurs in controlled studies, suggesting that clinicians need to pay close attention to the cerebrodynamic responses of each patient to any care maneuver. We recommend that future research regarding nursing care and ICP/CPP in TBI patients needs to have a more integrated approach, examining comprehensive care in relation to short- and long-term outcomes and incorporating multimodality monitoring. Intervention trials of care aspects within nursing control, such as the reduction of environmental noise, early mobilization, and reduction of complications of immobility, are all sorely needed.

Improvement of Non-Destructive Elastic Wave Detection Accuracy Based on Reduction of Environmental Noise Using the Akaike Information Criterion

Improvement of Non-Destructive Elastic Wave Detection Accuracy Based on Reduction of Environmental Noise Using the Akaike Information Criterion

Peculiarity of low noise pavement design under Lithuanian conditions

The paper gives a detailed overview and analysis of road transport noise propagation, noise composition and impacts on the living conditions. Road transport noise has been rapidly growing and the traditional noise abatement solutions, such as noise barriers, are not always suitable and cost-effective for particular road infrastructure. One of the most promising and effective solutions is the use of low noise pavements. Presently, low noise pavements are not being used in Lithuania but expected to have a good environmental noise reduction potential. However, the most effective low noise pavement solutions according to other European countries’ experience are not always applicable for Lithuanian road conditions. For these reasons, the authors developed a few low noise asphalt pavement mixtures designed to achieve a relatively high noise reduction effect and maintain sufficient mechanical and operational characteristics under Lithuanian conditions. Laboratory testing results (including mechanical and physical, noise reduction and durability characteristics) and comparison with traditional asphalt mixtures are provided in the paper as well as recommendations for the use of the developed low noise asphalt mixtures.