Influence of the tyre impedance on CPX level used to evaluate tyre/road noise

For traffic noise studies CPX measurements are used to evaluate the noise-reduction of a road surface.CPX measurements as described in ISO/DIS 11819-2 are carried out at microphone positions close to predefined tyres at constant speed. The dominant CPX sound source is the tyre’s rolling noise as a result of tyre/road interaction, which - apart from the acoustic properties of the road surface - is mainly determined by the properties of the tyre.To ensure continuous quality and comparability of CPX measurements, the variation of acoustically relevant properties of the reference tyres must be taken into account to reduce measurement uncertainties. Thus, to ensure comparability, the standard ISO/TS 11819-3 specifies Shore hardness values to be checked at regular intervals and compared with normative values. According to our experience in CPX-measurements, determining the Shore hardness of the tyres is not sufficient to describe the reference tyres’ acoustically relevant properties. So, as an additional parameter the mechanical impedance of different reference tyres was measured and compared to their Shore hardness and CPX levels on different road surfaces.Based on these results, conclusions are drawn about the usability of the tyre impedance to increase the quality and comparability of CPX measurements

Influence of the tyre impedance on CPX level used to evaluate tyre/road noise

For traffic noise studies CPX measurements are used to evaluate the noise-reduction of a road surface.CPX measurements as described in ISO/DIS 11819-2 are carried out at microphone positions close to predefined tyres at constant speed. The dominant CPX sound source is the tyre’s rolling noise as a result of tyre/road interaction, which - apart from the acoustic properties of the road surface - is mainly determined by the properties of the tyre.To ensure continuous quality and comparability of CPX measurements, the variation of acoustically relevant properties of the reference tyres must be taken into account to reduce measurement uncertainties. Thus, to ensure comparability, the standard ISO/TS 11819-3 specifies Shore hardness values to be checked at regular intervals and compared with normative values. According to our experience in CPX-measurements, determining the Shore hardness of the tyres is not sufficient to describe the reference tyres’ acoustically relevant properties. So, as an additional parameter the mechanical impedance of different reference tyres was measured and compared to their Shore hardness and CPX levels on different road surfaces.Based on these results, conclusions are drawn about the usability of the tyre impedance to increase the quality and comparability of CPX measurements

Influence of the opening width of transverse contraction joints on the acoustic characteristics of road surfaces made of cement concrete

Bei Entwicklung und Bau von Fahrbahndecken aus Beton wird angestrebt, die Rollgeräuschminderung über die moderate akustische Wirkung von Waschbeton hinaus zu steigern und die Reproduzierbarkeit, Homogenität und Dauerhaftigkeit der akustischen Oberflächeneigenschaften zu verbessern. In Feldmessungen wurde deutlich, dass Querscheinfugen im Moment des Überrollens kurzzeitig zu einer starken Anhebung des Rollgeräuschs führen können und die akustischen Eigenschaften einer Betonfahrbahndecke aufgrund des wiederholten Auftretens der Fugengeräusche entlang der Fahrbahn insgesamt verschlechtern können. Aufgabe war, den Einfluss der bautechnischen Eigenschaften von Querscheinfugen auf die Rollgeräuschentstehung zu untersuchen und Empfehlungen für die schalltechnische Optimierung bei der baupraktischen Ausführung der Fugen zu geben. Anhand von umfangreichen CPX-Messungen wurden 600 Fugen unterschiedlicher Ausführung und unterschiedlichen Zustands auf Betonfahrbahnen im deutschen Autobahnnetz schalltechnisch untersucht. An sechs ausgewählten Fugen wurden Detailuntersuchungen der Fugengeometrie und der Oberflächenstruktur sowohl der Fugen als auch der angrenzenden Fahrbahnoberflächen durchgeführt und durch detaillierte Messungen des Reifen-Fahrbahn-Geräuschs ergänzt. Neben der messtechnischen Analyse des Zusammenhangs zwischen Fugeneigenschaften und Rollgeräusch wurden die Messergebnisse dazu benutzt, ein bestehendes Rechenmodell für Reifen-Fahrbahn-Geräusche zu erweitern, zu validieren und für eine Parameterstudie zum Einfluss der Fugeneigenschaften auf das Rollgeräusch einzusetzen. Messungen und Parameterstudie zeigen, dass der Fugeneinfluss auf das Rollgeräusch umso größer wird, je leiser das Rollgeräusch aufgrund akustisch günstiger Oberflächentexturen zwischen den Fugen wird. Akustisch ungünstige Fugeneigenschaften begrenzen dann die Geräuschminderung einer Betonfahrbahndecke. Für die Parameter Fugenöffnungsweite, Anstellwinkel und Höhenversatz und für die Eigenschaften der Fugenfüllung werden konkrete Empfehlungen für eine schalltechnische Optimierung gegebenThe objective of development and construction of road surfaces made of cement concrete is to increase the reduction of the tyre/road noise beyond that of exposed aggregate cement concrete and to improve reproducibility, homogeneity and durability of the acoustic properties of the road surface. Field measurements have shown that transverse contraction joints give rise to a severe increase of the rolling noise when the tyre passes over the joint. Due to the recurrent occurrence of the joint noise along the road surface the acoustic behaviour of the cement concrete pavement can be impaired by the joints. Task in this project was to investigate the effect of geometric and structural characteristics of transverse joints on the generation of tyre/road noise and to provide recommendations for acoustically optimized constructions of the joints. By means of extensive CPX measurements a number of 600 transverse joints of different shape and in different condition on cement concrete pavements on German highways have been acoustically investigated. Six joints were selected to be investigated in more detail. The joint’s geometry and surface structure have been measured as well as the texture of the road surface adjoining the joints. Both CPX and SPB measurements were used to characterize the rolling noise generation. In addition to the measurement based analysis of the relation between joint properties and rolling noise the measurement results have been used to enhance and validate an existing computational model for tyre/road noise. A parameter study was then based on the model in order to investigate the sensitivity of the tyre/road noise to different parameters of the joint. Both measurements and the parameter study show that the impact of transverse joints on the rolling noise increases with decreasing rolling noise on the pavement’s surface between the joints what can be due to acoustically optimized textures. Acoustically inappropriate joint characteristics will thus limit the noise reduction potential of the cement concrete road pavement. For the purpose of acoustical optimization of the joint construction recommended values are given for the opening width, the skewing, the fault level and the characteristics of the sealant

Study of tire–pavement noise acoustic performance in resilient road pavement made of strain-hardening cementitious composites

A modified strain-hardening cementitious composite (SHCC) material, fabricated using corundum aggregates (SHCC-Cor), has been proposed for roadway applications as it offers high structural performance and high skid resistance. However, the acoustic performance of SHCC is unclear and has not been well studied in the past. Theoretically, SHCC may not provide the optimum solution in acoustic performance as it provides a low texture profile, high density, and low porosity. In this study, the acoustic performance of pavement slabs made of SHCC and modified SHCC-Cor are investigated using a nondestructive method to determine the surface roughness (macro texture) of slab surfaces. The pavement–tire noise level was then simulated using SPERoN software. As result, the noise level coming from the pavement made of SHCC could be up to 65 dB(A), while the noise level for SHCC-Cor increased up to 69.2 dB(A) because of the lower shape factor (G) due to a rougher surface as a result of the existence of corundum aggregate on the SHCC surface. The aeroacoustics were also increased compared to the SHCC slab. The modification of SHCC-Cor by introducing grooves (SHCC-Cor-Gro) successfully reduced the sound level coming from the vibration.National Research Foundation (NRF)Published versionThis work was financially supported by the Singapore National Research Foundation under its Campus for Research Excellence and Technological Enterprise (CREATE) program