Traffic noise is a major noise source in the study of environmental noise. Various noise generation mechanisms depict different spectral features. Some are wide-band noise, such as engine knocks; some have signature frequencies, such as gear transmissions; and some are in a certain frequency region, such as tire/road noise. These spectral features affect the façade design of a building in order to achieve sufficient exterior noise insulation and satisfactory interior noise due to the traffic noise. ISO standard 11819-1 specifies the measurement procedure of statistical pass-by tests. There are three ranges of vehicle speed: slow, medium, and fast. However, it requires that the vehicle must maintain constant speed when passing by the test point. Unfortunately, a vehicle tends to generate higher noise when accelerating, especially at low frequencies. Therefore, it is necessary to distinguish the noise levels at an intersection versus middle-points of the road between two intersections. Presumably, the traffic noise levels at an intersection would be higher. This research measured the traffic noise at various locations of different speed limits. Statistical analyses were conducted to compare the spectra at these locations. This is also an effort to refine the noise map.

Reducing tire noise has been a topic of increased focus in the recent years in industrial countries in order to decrease road traffic noise. Computational fluid dynamics (CFD) simulations conducted using ANSYS FLUENT are presented here to provide a better understanding of the small-scale noise generation mechanisms due to air-pumping at the tire-road interface. The CFD model employs a large eddy simulation (LES) turbulence modeling approach, where the filtered compressible Navier-Stokes equations are solved for simple groove geometries with a moving bottom wall that represents the deformation due to the tire movement along the road surface. A horizontally moving wall is used to represent the motion of the tire groove in and out of the contact patch while the deformation of the groove is prescribed. Temporal and spatially accurate pressure fluctuations are utilized to determine sound pressure levels and dominant frequencies. In addition to an understanding of noise generation mechanisms in such grooves, the CFD model developed here can potentially provide a series of control parameters that can help optimize the tire performance in terms of tire acoustics.

The goal of this work is to propose a new strategy for the attenuation of the traffic noise, which constitutes one of the main sources of acoustic pollution in urban and suburban areas. This strategy is based on the measurement of the noise radiated by each individual vehicle using an electro-acoustic system, composed of two microphones for the acquisition of the engine and of the rolling noise. These microphones have been situated inside the engine hood and close to the right back tire respectively. The signals have been recorded for diesel and petrol engines and through typical urban and suburban courses with different persons. Using this procedure, we aim to characterise the drivers responsible of the highest noise levels producing maximum annoyance. The near-field measurements have been then extrapolated to far field positions using an analytical filter that takes into account absorbing properties of the propagation floor. For the internal signal it has been necessary to characterise the acoustic properties of the engine hood experimentally using an array of microphones surrounding the vehicle. The propagated noise is calculated considering the absorption due to the geometrical divergence, the absorption by the air, and the effect of the propagating surface. The signals extrapolated to the receiver position could be compared with the current normative to propose recommendations concerning noise control actions.

Although tire/road noise and tire vibration phenomena have been studied for decades, there are still some missing links in the process of accurately predicting and controlling the overall tire/road noise and vibration. An important missing link is represented by the effect of rolling on the dynamic behavior of a tire. Consequently, inside the European seventh framework program, an industry-academia partnership project, named TIRE-DYN, has been founded between KU Leuven, Goodyear and LMS International. By means of experimental and numerical analyses, the effects of rolling on the tire dynamic behavior are quantified. This paper presents the results of vibration measurements on a rotating tire with an embedded accelerometer. Modal parameters of the rolling tire are estimated from an operational modal analysis. In addition, the dispersion curves, which give detailed insight in the wave propagation behavior of a structure, are analyzed for the rolling tire. The goal of these analyses is to deepen the understanding on the influence of rolling on the tire dynamic behavior.

Tire noise is one of the major causes of road traffic noise. The high-frequency component dominates tire radiation noise, which is caused by tire tread bending vibration excited by rough road surface textures. As a result of such complicated phenomena, including very complicated tread vibration modes in the high-frequency range, heavy damping, and non-periodic patterns of the road surface texture, the modal analysis approach may appear to have a low potential for analyzing this problem. Based on the above considerations, we attempted to model the tread vibration phenomenon as a group of traveling bending waves excited at an array of pavement chippings. By setting the tread shoulders as reflecting lines, the interference effect of diagonally propagating direct and reflected waves is clarified. The vibration propagation speed and decay rate were estimated through shaker tests. The shape of the probability distribution function of the chippings intervals affects the traveling wave patterns. These observations will help engineers to develop less noisy tires.

The coupling of the tire cavity and tire rim resonance imparts a force upon the wheel spindle which is transmitted to the vehicle interior to produce undesirable noise levels. Modifications to the tire rim or tire cavity can decouple these resonances by shifting the natural frequency outside of the 200–250 Hz range to reduce the audible noise levels. Through experiment and analysis several potential solutions have been compared for their commercial viability. Modifications of the rim included the Kühl wheel design and the implementation of a Helmholtz resonator, whilst tire cavity modifications included the extrusion of rubber from the tire into the cavity, the introduction of a sound absorption material and an elastic ring with separator fins which extends into the cavity due to centrifugal forces. Through QFD analysis the elastic ring design was found to be most commercially viable in terms of performance, cost, safety, versatility, durability and manufacturing readiness.

The consumer today places greater demands upon the vehicle acoustical engineer than in the past. Product quality has always been associated with a quiet ride. Automotive engineers recognize that the predominant sources of vehicle interior noise are wind, tire-road or rolling noise, and the powertrain. This paper suggests a test protocol for measuring wind and rolling noise using a chassis rolls dynamometer and road tests. Automotive engineers are frequently confronted by customer complaints concerning wind noise. Usually, engineers resort to using wind tunnels to address these concerns and to conduct diagnostic studies to remedy wind noise problems. Unfortunately, wind tunnels are expensive to rent and difficult to schedule. As an alternative, the engineer can learn a great deal about the wind noise of a vehicle by using a chassis rolls dynamometer along with road tests [1,2]. If the chassis rolls surface texture closely matches that of the road surface, the tire-road or rolling noise signal in both situations can be assumed to be equivalent. The powertrain noise source can be minimized by shifting the vehicle into neutral and coasting. Wind noise is a source for the road measurements, but not for the chassis rolls. Hence, the wind noise can be calculated by measuring the cab interior noise for both operating conditions, and subtracting the rolling noise measured on the chassis rolls. The two vehicles tested in this study included a pickup truck and a sport utility vehicle. The acoustical data revealed significantly different rolling and wind noise characteristics. The pickup truck had significantly louder rolling noise, and the wind noise was dominated by low frequency sound. The sport utility vehicle was much quieter overall and was significantly quieter for rolling noise than the pickup. The wind noise of the sport utility vehicle also was dominated by high frequency components. Both vehicles showed that rolling and wind noise trends increase linearly with speed. However, the slope of wind noise data for the sport utility vehicle was much steeper than the pickup, which suggested that it was more sensitive to wind noise as speed increased. Exterior noise data from both vehicles showed that the tire-road signal from the road differed significantly from that of the chassis rolls dynamometer. Rolling & wind noises will become even more critical as the motor vehicle industry adopts hybrid electric and, in the future electric fuel cell vehicles, because powertrain noise sources in the vehicle will likely be reduced. The procedure suggested here provides an inexpensive simple approach to assessing rolling and wind noise in the vehicle.