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.
Noise maps and action plans represent the main tools in the fight against citizens' exposure to noise, especially that produced by road traffic. The present and the future in smart traffic control is ...represented by Intelligent Transportation Systems (ITS), which however have not yet been sufficiently studied as possible noise-mitigation tools. However, ITS dedicated to traffic control rely on models and input data that are like those required for road traffic noise mapping. The present work developed an instrumentation based on low-cost cameras and a vehicle recognition and counting methodology using modern machine learning techniques, compliant with the requirements of the CNOSSOS-EU noise assessment model. The instrumentation and methodology could be integrated with existing ITS for traffic control in order to design an integrated method, which could also provide updated data over time for noise maps and action plans. The test was carried out as a follow up of the L.I.S.T. Port project, where an ITS was installed for road traffic management in the Italian port city of Piombino. The acoustic efficacy of the installation is evaluated by looking at the difference in the acoustic impact on the population before and after the ITS installation by means of the distribution of noise exposure, the evaluation of G
and G
, and the calculation of the number of highly annoyed and sleep-disturbed citizens. Finally, it is shown how the ITS system represents a valid solution to be integrated with targeted and more specific sound mitigation, such as the laying of low-emission asphalts.
Abstract
This paper proposes a system based on Neural Networks (NN), designed for providing an efficient, non-invasive and automated method for monitoring the health status of road pavements by using ...features derived from Tyre Cavity Noise (TCN) analysis. Indeed, visual inspection remains to date the most common choice for evaluating the condition of road pavements; however, this method is both labor intensive and time consuming. The system presented in this work uses a microphone placed inside the vehicle tyre that measures TCN while travelling normally, and an embedded data acquisition system based on a Raspberry Pi which feeds the NN tools to recognize and classify road deterioration. We also present a preliminary analysis of features based on temporal and spectral characteristics of TCN signals generated by tyre/road interaction and acquired on three different kind of road distresses. The results show good classification capability and, moreover, the sound pressure measured inside the tyre was correlated accelerometric data measured on-board.
•The use of low-noise surfaces is the best solution to mitigate tyre/road noise.•Green Public Procurement (GPP) requires CPX measurements on new low-noise pavements.•Modelling CPX levels in function ...of the mix properties is necessary to reduce costs.•Two models were elaborated, using two frequency separations for tyre/road noise.•The variables used are related to volumetric and composition properties of the mix.
Road traffic in urban contexts produces noise mainly by the interaction of tyres with pavement surface and, therefore, the use of low-noise surfaces represents the best solution since they aim to mitigate the source. Moreover, in urban contexts it is often the only viable solution, together with a careful traffic planning. The main challenge in their adoption as noise mitigation actions is to be able to forecast the acoustical performances that the new road surface will be able to offer. In the UE, the new Green Public Procurement requires experimental verification of noise performance compliance: the designer must declare the acoustical performance of the proposed low-noise pavement and, a few months after the laying, the actual performance of the road surface must be tested using the Close Proximity Method (CPX). Due to the importance of being able to forecast CPX levels, the present work reports a novel way to model CPX broadband levels of newly laid low-noise road surfaces using only data available to the designer before the laying or easily obtained through coring tests, such as grading curve, fractal dimension, asphalt binder content, air voids, voids in mineral aggregates. Two models were elaborated, using two different frequency separations for tyre/road noise. The first model separates low and high frequency contributions, while the second one also considers noise around 1 kHz separately, using a three-band model. Both models are capable of forecasting the acoustic performance of newly laid low-noise road surfaces, using different road mixture parameters at different frequency ranges. The three band model shows a lower RMSE.
Road traffic noise is the most common source of environmental pollution in urban areas, and therefore, the study of noise mitigation actions is fundamental for urban planning. The use of low noise ...road surfaces is one of the most widespread intervention since it acts directly on the source of road traffic noise, represented by tyre/road interaction. In this work, the interaction between texture and tyre/road noise was studied from an experimental point of view, by comparing CPX and road texture measurements on rubberised and standard road surfaces. Tyre deformation was addressed by taking into account the indenter method proposed by Sandberg and Goubert in 2018. Regressions of CPX and enveloped road texture levels were performed separating rubberised from reference surfaces, and parallelism tests were performed on the slopes. Results show that the use of rubber influences the interaction of road texture and noise, especially at high frequencies.
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•A normalised method for Tyre Cavity Noise measurements is not available.•Based on an existing CPX method, a normalisation procedure was designed.•This method was used on 24 road ...surfaces, together with CPX and texture measurements.•Results show that TCN is correlated to road texture levels within the 100 mm band.•TCN measurements could represent an adequate tool for road surface monitoring.
In this work, a protocol to study Tyre Cavity Noise (TCN) was developed. Using this new method, TCN was measured on 24 different road pavements, together tyre noise emission measured with the Close-Proximity (CPX) method and road texture measurements. The results were used to model the relationship between TCN and road surface parameters. The analysis shows that the Standard Reference Test Tyre’s (SRTT) TCN is correlated to megatexture at low frequencies and that the correlation between TCN and outside noise emission is significant for frequencies lower than 1 kHz. The use of sensors placed inside the tyre for monitoring the acoustic performance of road pavements presents several advantages compared to the CPX method, such as a more compact design, lower cost and lower hazards both for the instrumentation and for other vehicles.
Container ships emit airborne noise that can vary significantly due to diverse vessel characteristics and operating conditions. This study aims to investigate the factors influencing noise emission ...from container ships moving in ports to enhance our understanding and improve noise prediction models. Using a dataset comprising long-term sound pressure level measurements, video recordings, and weather station data, a multiple regression analysis was conducted to assess the impact of static (ship-specific) and dynamic (pass-by specific) variables on noise emission. Static variables included ship dimensions and age, while dynamic variables encompassed distance from the microphone, speed, and draught. A k-means unsupervised clustering analysis was performed using 1/3rd octave band spectra to identify subcategories of container carriers based on sound emission characteristics. Significant correlations between emissions and both static and dynamic variables were found. The k-means clustering analysis yielded distinct subcategories of container carriers based on their sound emission profiles. This study highlights the importance of considering various factors, including ship characteristics and operating conditions, when assessing noise emission from container ships. By better understanding the factors contributing to noise emission, we can effectively mitigate noise pollution and minimize the impact on surrounding communities.
•Airborne noise emissions from container ships moving in ports can be impactful on population.•Detailed sound power levels and 1/3rd octave band spectra have been calculated for different vessels’ categories.•A multiple regression analysis investigated the effect of ship-specific and pass-by specific variables on emissions.•K-means unsupervised clustering identified subcategories of container carriers based on sound emission characteristics.•Vessel characteristics and operating conditions are important parameters for large such sound emitters.
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