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06.02 Road Noise Treatment

Implementing auralized CPB sounds on a pedestrian simulator
Time: 12:20 pm

Author: Francisco Soares

Abstract ID: 2304

Recently, several studies on pedestrian safety and particularly those addressing pedestrian crossing behaviour and decision-making, have been performed using virtual reality systems. The use of simulators to assess pedestrian behaviour is conditioned by the feeling of presence and immersion, for which the sound is a determining factor. This paper presents an implementation procedure in which tyre-road noise samples are auralized and presented as auditory stimuli in a virtual environment, for assessing pedestrian crossing decision-making. The auditory samples obtained through the Close Proximity (CPX) method and subsequently auralized to represent Controlled Pass-By (CPB) sounds reproduce the sounds of a vehicle approaching a crosswalk. The auralized sounds together with the presentation of visual stimuli composed an experiment which was carried out with 30 participants. Safety indicators, as the time-to-passage at the moment that participants decided to cross a virtual crosswalk and the minimum time-to-collision were registered and compared with data obtained in real-world road crossings. A comparison with real world data points to a close alignment between results obtained in virtual and real environments, indicating a good suitability of the approach for studying pedestrian crossing behaviour.

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Extensive study of receiver point interpolation methods for drawing estimated road traffic noise maps in Japanese city blocks.
Time: 7:20 pm

Author: Yamashiro Yudai

Abstract ID: 2663

There are various issues need to be addressed when drawing estimated road traffic noise maps in Japan. One of them is there is a trade-off between computational load and estimation accuracy due to the number of sound receiver points on the building facades where the noise exposure is evaluated. An interpolation to generate receiver points on facades as post-processing of a computation made on relatively coarse receiver points can be a solution to achieve compromise between computational load and estimation accuracy. In this study, estimated noise maps are drawn in nine real city blocks in Japan with different land-use areas by placing sound receiving points with intervals of 1m, 5m and 10m. The map of the 1m interval is used as the reference noise levels. The maps of the 5m and 10m intervals are interpolated to the 1m interval using 29 interpolation methods. The optimal combination of the interval of sound receiving points and the interpolation method are found based on error of the interpolated maps compared to the reference map.

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The Performance of a Low Berm in Reducing Traffic Noise
Time: 8:00 am

Author: Carrie Janello

Abstract ID: 1783

Traffic noise measurements were made behind a low, earth berm and in an adjacent open field to estimate insertion loss.  The traffic was comprised of a mix of light vehicles, heavy trucks, and some medium trucks. The berm had a height of 1.65 meters above the roadway and began at the outside shoulder of a four-lane highway along U.S. Highway 101 in Northern California.  Two microphone positions were located on the far side of the berm at distances of 28 and 40 meters from the center of the near lane of vehicular traffic. Away from the berm, a microphone was placed in an open field at 28 meters from the highway at a site upstream of the berm. The difference between the open location and those behind the berm were 11.6 and 9.9 dB for the 28- and 40-meter locations, respectively. The reductions obtained with the berm are compared to double edge diffraction theory and acoustic scale model results from the literature. The results of this study are reviewed in this paper and a comparison to FHWA Traffic Noise Model results is presented.

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Corn plants as temporary acoustic barrier to limit the effects of noise pollution
Time: 7:20 am

Author: Gino Iannace

Abstract ID: 2066

Corn is a cereal imported into Europe from the Americas and is used for human and animal feed, but there are also industrial uses such as the production of ethanol, as a fuel for heating homes or to produce starch. Corn grows in the summer in areas where there is water. Corn is grown in many regions of the world and its production exceeds that of any other cereal in quantity. The corn plant can reach up to three meters in height, with a stem diameter of a few centimeters and with dense leaves longer than 30 cm and 10 cm wide. There are noisy activities where it is necessary to attenuate the noise produced to limit the effects of noise pollution. Some activities use temporary barriers depending on the processing cycle adopted. If noisy work is carried out during the summer season, corn rows of adequate width can be used as an acoustic barrier. In this paper, the possibility of using corn plants as an acoustic barrier is investigated. The acoustic measurements of the noise attenuation of corn rows of adequate width are described. Using a semi-spherical source placed on the ground, the acoustic attenuation due to the corn plants arranged in several rows for different distances from the sound source to the receiver was measured.

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Confusion in the evaluation of sound barriers under harmonized standard
Time: 7:00 am

Author: Pavel Rubáš

Abstract ID: 2105

After the obligatory introduction of the declaration of uncertainty in EN 1793-2:2018, the B categories shall not be used to prevent further confusion. Contrary to the updated standard, B categories remain a ubiquitous contractual criterion in the Czech Republic. Contractors continue to request insulation category B3 products determined according to the cancelled EN 1793-2:1997. The current standard only specifies a test method for determining the intrinsic airborne sound insulation performance of noise barriers designed for tunnel roads, deep trenches or covered spaces. EN 1793-6:2018 shall be used for barriers designed for non-reverberant conditions. Notified bodies involved in barriers testing should exercise care and analyze whether supporting test standards in the cancelled but still harmonized EN 14388:2005 can be used or whether the latest testing procedures will be considered. A guidance document is vital because the situation is becoming increasingly confusing. Common rules should be established across the EU to prevent invalid contractual requirements concerning B3 category barriers designed for non-reverberant conditions. The paper analyzes the current unsatisfactory situation, discusses the application of single number rating involving uncertainties, and proposes decision rules for logical and illogical contractual requirements.

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Comparison of Noise Reduction Performance Evaluation Methods for Low-Noise Pavement in Korea- Part ?
Time: 6:00 am

Author: Hyunjin Kim

Abstract ID: 2260

In Korea, road noise is assessed as a measurement method of exterior noise emitted by road vehicle for management standards by the National Institute of Environmental Sciences. In this method, the noise felt at the actual pickup point is measured as LAeq (the roadside equivalent noise level). Recently, to clarify the standard for measuring noise on low-noise pavements, the CPX (ISO11819-2; Close-proximity method) was first introduced in the Porous Pavement Guidelines of the Ministry of Land, Infrastructure and Transport. According to ISO, the CPX adopts the side microphone as a mandatory measurement location, and the rear optional. The side location has been a mandatory due to its high correlation with SPB (ISO 11819-1, Statistical Pass-by method). However, according to our previous study on the correlation evaluation between L and CPX rear microphone noise level, both noise reduction effect was about 9-12 dB(A) showed a high correlation in Korea where heavy road traffic is common. The following study aims to show the consistent correlation between the L and CPX rear noise level. Furthermore, it is intended to be helpful in selecting the location of the CPX microphone that can most effectively represent the actual noise on the low-noise pavement in Korea.

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Noise reduction of Parallel barrier integrated with compact flexible panel device
Time: 6:20 am

Author: Yat Sze Choy

Abstract ID: 2268

Erection of parallel barriers to control environmental noise such as traffic noise and construction noise is commonly seen in community. Owing to the formation of multiple reflection waves between the parallel barriers, their performance may be worse than a single barrier. To improve the performance of parallel barriers, a small piece of flush-mounted panels backed by a slender cavity in an otherwise rigid wall of barriers is proposed.  With the excitation of the incident wave from a sound source inside parallel barriers, the flexible panel vibrates and sound is radiated out to undergo acoustics interference with sound field between the parallel barriers so that the sound intensity in this space and diffraction wave at the barrier top edge is reduced over a broadband in the low-frequency regime. The use of the panel provides flexibility in controlling range of stopband with high insertion loss by varying mass and bending stiffness. A semi-analytical model for dealing with vibroacoustic coupling between the open cavity and vibrating panel in a two-dimensional configuration is established in order to understand the sound suppression mechanism within the shadow zone. With the optimal structural properties of the panel, the extra averaged insertion loss of about 5dB in the frequencies ranging from 50 to 1000 Hz is reached for the parallel barrier.

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Empirical study on the correlation between measurement methods under diffuse and direct sound field conditions for determining sound absorption and airborne sound insulation properties of noise barriers
Time: 6:40 am

Author: Andreas Fuchs

Abstract ID: 2383

In the frame of the SOPRANOISE project (funded by CEDR in the Transnational Road Research Programme 2018) the database of the European noise barrier market developed during the QUIESST project was updated with newly acquired data. This database gives the opportunity for an empirical study on the correlation between the different measurement methods for the acoustic properties of noise barriers (according to the EN 1793 series) to further investigate the interrelationships between these methods by using single-number ratings and third-octave band data. First a correlation of the measurement methods for sound absorption under diffuse field conditions (EN 1793-1) and sound reflection under direct sound field conditions (EN 1793-5) is presented. Secondly, a correlation of the measurement methods for airborne sound insulation under diffuse field conditions (EN 1793-2) and airborne sound insulation under direct sound field conditions (EN 1793-6) is shown. While for airborne sound insulation a distinct correlation is found due to the wide data range, for sound absorption no robust correlation can be found.

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Control of low frequency noise from an environmental test facility
Time: 7:40 am

Author: Malcolm Smith

Abstract ID: 2421

Environmental test chambers are used in the automotive industry to verify the resilience of vehicles.  In just a few hours it is possible to take a car from mid-winter in the artic, via a high mountain range, to mid-summer in a desert.  Powerful ventilation systems are used to change the temperature, pressure and humidity of the air in the chamber, and the variable speed blowers are a major source of low frequency noise, which can cause significant disturbance at neighbouring properties if there are gaps in silencer performance.  This paper details a study to assess the attenuation requirements for a system to meet a standard criterion for low frequency far-field noise levels, and to select a reactive silencer system to achieve that specification under all circumstances.  The system used standard silencer components where possible, but needed to take account of long pipe runs through the facility, with tailpipe resonances being a particular issue, and was further constrained by space and loading limits for the building.   Design layouts were verified using the Actran FE code, taking account of interactions with existing silencers and transfer functions to the far-field, in order to have very high confidence of a successful outcome.

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