Use of Noise Barriers for Helicopter Noise Mitigation

The possibility of using noise barriers for helicopter noise mitigation is numerically investigated. The noise field produced by an isolated main rotor in the presence of a barrier on the ground is predicted by employing and appropriately modifying existing diffraction and reflection models. It is shown that noise barriers can provide substantial shielding from helicopter noise and conclusions are drawn regarding barrier configuration and helicopter operations.

Download Full-text

Finite Element Method for the Estimation of Insertion Loss of Noise Barriers: Comparison with Various Formulae (2D)

Urban Science ◽

10.3390/urbansci4040077 ◽

2020 ◽

Vol 4 (4) ◽

pp. 77

Author(s):

Nikolaos M. Papadakis ◽

Georgios E. Stavroulakis

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Insertion Loss ◽

Rural Areas ◽

Analytic Solution ◽

Acoustic Radiation ◽

Real Life ◽

Noise Mitigation ◽

Noise Barriers ◽

Element Method

Noise barriers are a critical part of noise mitigation in urban and rural areas. In this study, a comparison of the insertion loss calculations of noise barriers via the Finite Element Method (FEM) and various formulae (Kurze–Anderson, ISO 9613-2/Tatge, Menounou) is presented in the case of two-dimensional acoustic radiation problems. Some of the cases explored include: receiver in the illuminated zone, in the shadow zone, in the shadow border, source in medium, long, short distance from the barrier, source and receiver near barrier, and source above the barrier. Comparisons of the results indicate that FEM results comply well (less than 1 dB in each case) with Menounou’s formula which in turn complies with the analytic solution (MacDonald Solution). In certain cases, the differences between FEM and Menounou’s formula compared to Kurze–Anderson and ISO 9613-2/Tatge formulae are substantial (source and receiver near the barrier (10 dB) and source near the barrier and receiver in the shadow border (5 dB)). Similar differences are also confirmed by the analytic solution. The findings suggest that FEM can be applied effectively for the precise estimation of the insertion loss of noise barriers. Especially in cases where ISO 9613-2 formula shows large deviations from the analytic solution (e.g., near barrier), possible applications may arise in cases such as balconies, facades, etc. Furthermore, the study supports the idea that FEM could possibly be effectively utilized in real life applications for microscale urban acoustic modeling as a viable alternative to expensive noise prediction software.

Download Full-text

Traffic Noise Mitigation Using Single and Double Barrier Caps of Different Shapes for an Extended Frequency Range

Applied Sciences ◽

10.3390/app10175746 ◽

2020 ◽

Vol 10 (17) ◽

pp. 5746 ◽

Cited By ~ 1

Author(s):

Domingo Pardo-Quiles ◽

José-Víctor Rodríguez ◽

Jose-Maria Molina-García-Pardo ◽

Leandro Juan-Llácer

Keyword(s):

Road Traffic ◽

Traffic Noise ◽

Noise Mitigation ◽

Noise Barriers ◽

Double Barrier ◽

Noise Abatement ◽

Extended Frequency ◽

Different Shapes ◽

The Aesthetic ◽

Insertion Losses

The primary function of noise barriers is to shield inhabitants of affected areas from excessive noise generated by road traffic. To enhance the performance of noise barriers while simultaneously adhering to height restrictions, the attachment of structures (caps) of different shapes to the tops of conventional screens can be considered. These caps can significantly impact the diffracted sound energy, thereby increasing the desired global acoustic losses. This work presents a comprehensive study of the acoustic performance of noise barriers with single and double attached caps of different shapes through a calculation of their insertion losses (IL). This study comprehensively addresses and compares different types, sizes, combinations, and numbers of noise barrier caps for different scenarios (including sloping and absorbent grounds) and sources (“car” and “ambulance”) for an extended frequency band up to 10 kHz. To the best of the authors’ knowledge, this is a range that has not previously been analyzed. A variety of different cap shapes were considered including cylinders, rectangles, trapezoids, and Y/T-shaped forms. To calculate the IL, an innovative and fast uniform theory of diffraction (UTD)-based method developed by the authors was applied in all simulations. The results showed that the Y-shaped single and double barrier caps were, in general, the most effective at increasing IL without raising the height of the barrier, thereby successfully managing the aesthetic impact. The results also showed how the consideration of sloping and absorbent floors could also contribute to improved noise abatement.

Download Full-text

Helicopter noise footprint prediction in unsteady maneuvers

International Journal of Aeroacoustics ◽

10.1177/1475472x17709927 ◽

2017 ◽

Vol 16 (3) ◽

pp. 165-180 ◽

Cited By ~ 3

Author(s):

Massimo Gennaretti ◽

Giovanni Bernardini ◽

Jacopo Serafini ◽

Alessandro Anobile ◽

Sander Hartjes

Keyword(s):

Near Field ◽

Solution Process ◽

Solution Procedure ◽

Noise Model ◽

Main Rotor ◽

Helicopter Noise ◽

Helicopter Flight ◽

Atmospheric Propagation ◽

Numerical Predictions ◽

Field Noise

This paper investigates different methodologies for the evaluation of the acoustic disturbance emitted by helicopter’s main rotors during unsteady maneuvers. Nowadays, the simulation of noise emitted by helicopters is of great interest to designers, both for the assessment of the acoustic impact of helicopter flight on communities and for the identification of optimal-noise trajectories. Typically, the numerical predictions consist of the atmospheric propagation of a near-field noise model, extracted from an appropriate database determined through steady-state flight simulations/measurements (quasi-steady approach). In this work, three techniques for maneuvering helicopter noise predictions are compared: one considers a fully unsteady solution process, whereas the others are based on quasi-steady approaches. These methods are based on a three-step solution procedure: first, the main rotor aeroelastic response is evaluated by a nonlinear beam-like rotor blade model coupled with a boundary element method for potential flow aerodynamics; then, the aeroacoustic near field is evaluated through the 1A Farassat formulation; finally, the noise is propagated to the ground by a ray tracing model. Only the main rotor component is examined, although tail rotor contribution might be included as well. The numerical investigation examines the differences among the noise predictions provided by the three techniques, focusing on the assessment of the reliability of the results obtained through the two quasi-steady approaches as compared with those from the fully unsteady aeroacoustic solver.

Download Full-text

Numerical Analysis of Acoustic Barriers with a Diffusive Surface Using a 2.5D Boundary Element Model

Journal of Computational Acoustics ◽

10.1142/s0218396x15500095 ◽

2015 ◽

Vol 23 (03) ◽

pp. 1550009 ◽

Cited By ~ 5

Author(s):

C. Prieto Gajardo ◽

L. Godinho ◽

P. Amado-Mendes ◽

J. M. Barrigon Morillas

Keyword(s):

Numerical Model ◽

Element Model ◽

The Body ◽

Noise Mitigation ◽

Noise Barriers ◽

Accurate Analysis ◽

The Road ◽

Body Of Knowledge ◽

Surface Profiles ◽

Computational Analyses

Acoustic barriers are a well-known environmental noise mitigation solution, which is widely used nowadays. In this work, it is expected to contribute to the body of knowledge regarding the physical and technical behavior of those barriers by developing and implementing a set of models that allow an accurate analysis of noise barriers with new configuration types. A 2.5D boundary-only numerical model is developed and implemented, and computational analyses are performed in order to compare different surface profiles of the acoustic barriers. The particular case in which two acoustic barriers are used, one at each side of the road, is addressed.

Download Full-text

Recent Developments in Sonic Crystals as Barriers for Road Traffic Noise Mitigation

Environments ◽

10.3390/environments6020014 ◽

2019 ◽

Vol 6 (2) ◽

pp. 14 ◽

Cited By ~ 28

Author(s):

Luca Fredianelli ◽

Alessandro Del Pizzo ◽

Gaetano Licitra

Keyword(s):

Insertion Loss ◽

Road Traffic ◽

Traffic Noise ◽

Porous Coating ◽

Road Traffic Noise ◽

Noise Mitigation ◽

Noise Barriers ◽

Continuous Growth ◽

Sonic Crystal ◽

Sonic Crystals

Noise barriers are the most widespread solution to mitigate noise produced by the continuous growth of vehicular traffic, thus reducing the large number of people exposed to it and avoiding unpleasant effects on health. However, conventional noise barriers present the well-known issues related to the diffraction at the edges which reduces the net insertion loss, to the reflection of sound energy in the opposite direction, and to the complaints of citizens due to the reduction of field of view, natural light, and air flow. In order to avoid these shortcomings and maximize noise abatement, recent research has moved toward the development of sonic crystals as noise barriers. A previous review found in the literature was focused on the theoretical aspects of the propagation of sound through crystals. The present work on the other hand reviews the latest studies concerning the practical application of sonic crystal as noise barriers, especially for road traffic noise mitigation. The paper explores and compares the latest developments reported in the scientific literature, focused on integrating Bragg’s law properties with other mitigation effects such as hollow scatterers, wooden or recycled materials, or porous coating. These solutions could increase the insertion loss and frequency band gap, while inserting the noise mitigation action in a green and circular economy. The pros and cons of sonic crystal barriers will also be discussed, with the aim of finding the best solution that is actually viable, as well as stimulating future research on the aspects requiring improvement.

Download Full-text

Evaluation on the effectiveness of noise barriers for road traffic noise mitigation

10.5353/th_b3125397 ◽

1998 ◽

Author(s):

Pak-lam Chau

Keyword(s):

Road Traffic ◽

Traffic Noise ◽

Road Traffic Noise ◽

Noise Mitigation ◽

Noise Barriers

Download Full-text

Traffic-Noise Impact Study for Least Bell's Vireo Habitat along California State Route 83

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198196155900101 ◽

1996 ◽

Vol 1559 (1) ◽

pp. 3-7

Author(s):

Douglas E. Barrett

Keyword(s):

Habitat Restoration ◽

Traffic Noise ◽

Mitigation Measures ◽

Department Of Transportation ◽

Noise Mitigation ◽

Noise Barriers ◽

California Department ◽

Noise Impact ◽

The Impact ◽

Mitigation Projects

A traffic-noise study was conducted to determine the impact that a highway reconstruction project would have on a habitat area for the least Bell's vireo, a federally protected songbird. FHWA and California Department of Transportation policies do not address the impact of noise on wildlife species; the study was conducted in response to a requirement of the U.S. Fish and Wildlife Service. Several mitigation measures were considered, including approximately 1200 m (4,000 ft) of temporary noise barriers. The outcome of the study was to provide funds for in-kind mitigation through habitat restoration rather than direct mitigation of noise impacts. This study contributes to a growing precedent of considering noise mitigation specifically for the protection of wildlife and raises several policy issues. Despite the increasing number of noise-mitigation projects for endangered birds and the commitment of significant funds to these undertakings, there remains a lack of firmly based noise-impact criteria and guidelines for noise mitigation.

Download Full-text