Railway ground vibration and mitigation measures: benchmarking of best practices

Vibration and noise aspects play a relevant role in the lifetime and comfort of urban areas and their residents. Among the different sources, the one coming from the rail transit system will play a central concern in the following years due to its sustainability. Ground-borne vibration and noise assessment as well as techniques to mitigate them become key elements of the environmental impact and the global enlargement planned for the railway industry. This paper aims to describe and compare the different mitigation systems existing and reported in literature through a comprehensive state of the art analysis providing the performance of each measure. First, an introduction to the ground-borne vibration and noise generated from the wheel-rail contact and its propagation through the transmission path is presented. Then, the impact and the different ways of evaluating and assessing these effects are presented, and the insertion loss indicator is introduced. Next, the different mitigation measures at different levels (vehicle, track, transmission path and receiver) are discussed by describing their possible application and their efficiency in terms of insertion loss. Finally, a summary with inputs of how it is possible to address the future of mitigation systems is reported.

Guidelines for the LTO Noise Assessment of Future Civil Supersonic Aircraft in Conceptual Design

One of the most critical regulatory issues related to supersonic flight arises from limitations imposed by community noise acceptability. The most efficient way to ensure that future supersonic aircraft will meet low-noise requirements is the verification of noise emissions from the early stages of the design process. Therefore, this paper suggests guidelines for the Landing and Take-Off (LTO) noise assessment of future civil supersonic aircraft in conceptual design. The supersonic aircraft noise model is based on the semi-empirical equations employed in the early versions of the Aircraft NOise Prediction Program (ANOPP) developed by NASA, whereas sound attenuation due to atmospheric absorption has been considered in accordance with SAE ARP 866 B. The simulation of the trajectory leads to the prediction of the aircraft noise level on ground in terms of several acoustic metrics (LAmax, SEL, PNLTM and EPNL). Therefore, a dedicated validation has been performed, selecting the only available supersonic aircraft of the Aircraft Noise and Performance database (ANP), that is, the Concorde, through the matching with Noise Power Distance (NPD) curves for LAmax and SEL, obtaining a maximum prediction error of ±2.19%. At least, an application to departure and approach procedures is reported to verify the first noise estimations with current noise requirements defined by ICAO at the three certification measurement points (sideline, flyover, approach) and to draw preliminary considerations for future low-noise supersonic aircraft design.

Road traffic noise assessment in a hospital area in Umuarama - Brazil

In hospital environments, high noise levels can result in damage to patients' treatments, delaying their rest and recovery. The sound pressure level (SPL) in hospital areas during the day must not exceed 50 dB and 45 dB (A) at night, according to NBR 10.151/2019. This research aimed to carry out environmental monitoring of equivalent sound pressure levels (LAeq) at fifteen points in the vicinity of three hospitals in the central region of the municipality of Umuarama-PR, during working days, at four different times, in the months of August, September and November 2018 and continued in March 2019. To this end, we sought to map the LAeq of the points, compare them with data from municipal and federal legislation and relate the LAeq to the volume of vehicular traffic. The collected SPL were higher than recommended by NBR 10.151 at all times and measurement points, during the week, and when considering the municipal regulations, only one point is in the equipment's accuracy limit. From the statistical analysis, a very strong correlation was observed between LAeq and the total volume of vehicles, and also a strong correlation between the descriptors L10 and L50 and the volume of vehicles. The Traffic Noise Index (TNI) was also calculated and the LAeq values ​​were compared with a subjective noise rating. The results show a scenario of noise pollution in the area and there is a need for the application of mitigating measures.

Research of road transport noise load in the central part of the City of Poltava

The studies were conducted in accordance with the requirements set out in the Declaration of the European Union "On Environmental Noise Assessment" and are closely related to finding solutions of the problems set out in the Law of Ukraine "On Ensuring Sanitary and Epidemic Welfare of the Population". The paper presents experimental and calculation studies on the assessment of noise pollution in the central part of Poltava. The results of such studies confirmed the hypothesis of exceeding the normative values of noise levels within some sections of the streets and directly at the intersections. It was found that the main causes of noise pollution include high intensity of public and light commercial transport means, large number of intersections and stops, poor road surface, as well as lack of acoustic protection, including lack of landscaping along roadsides. The research visually characterizes and investigates the boundaries of acoustic pollution areas distribution. Exceedence of the noise pollution normative values extends to the distance of up to 150 m from the experimental study points. The study determines the number of residents of the district who fall into high noise load areas and estimates the magnitude of risks to health of the citizens living within such areas. Experimental studies established a link between a negative impact of external noise generated by urban vehicles and urban residents' health state that requires hygienic research with application of WHO-recommended risk analysis methodology. It was found that almost 5,000 people from the study area spend most of their lives in the neighbourhoods where the noise level exceeds the permissible value of 55 dBA. Almost 2,000 of them live in the houses where penetrating noise exceeds the value of 40 dBA. Based on the results of theoretical provisions and conclusions, certain practical recommendations for management of noise pollution risks in the urban area were developed.

Helicopter Inside Cabin Acoustic Evaluation: A Case Study—IAR PUMA 330

This paper presents an inside-cabin acoustic evaluation of the IAR PUMA 330 helicopter, manufactured by IAR S.A. Brasov. In this study, based on the acoustic assessment inside the helicopter, areas with high noise levels are identified. In this regard, several tests were carried out in accordance with the ISO 5129 standard. In the first stage of the assessment, a measurement campaign was performed to identify the acoustic leaks from the outside noise sources propagating inside the cabin (in the door area) and the acoustic attenuation of the helicopter structure. These tests were performed on the factory runway, with the helicopter in parked position (ground tests). During the ground tests, the helicopter engines were turned off. The tests consisted of placing two loudspeakers directed towards the helicopter door and generating pink noise. Inside the helicopter, the entire door frame opening was scanned with an intensity probe to identify acoustic leaks areas. The second assessment stage was to determine the areas of the cabin with the highest levels of noise. Within the measurement campaign, 16 microphones were placed inside the cabin, at the level of the passengers’ heads, arranged in seven zones. The tests were carried out with the helicopter engines started, staying at fixed point above the ground (hovering), and then a flight test, in which all the maneuvers necessary for the use of the helicopter were performed (in-flight tests). Based on the measurement results, it was possible to highlight the noise spectral components in each of the seven areas. The noise assessment revealed high noise levels inside the cabin, having as main noise sources the transmission gear and the door area, leading to the need for reducing the noise exposure for passengers and crew, thus the need to reduce noise levels inside the helicopter.