Numerical computation of tyre radiaion noise: a comparative study of different techniques

Increasingly stringent noise regulations concerning automotive vehicles particularly in Europe are forcing Tyre manufacturers as well as the automotive manufacturers to reduce radiated noise. With the future moving towards electric/hybrid vehicles, the ever present tyre noise will become more dominant. Even in the case of automotive engines running on fossil fuels, tyre noise dominates above speeds of 40 Km/h. Understanding the causes of tyre noise is the first step towards finding engineering solutions to reduce it. Numerical modelling can help the tyre engineer in understanding the causes of tyre-road noise with a design tool. In the present work, the noise radiated by the tyre surface is computed numerically using three different computational techniques. Both the time domain approach and the frequency domain approaches are used and the results are compared. The input structural vibrations are computed in ABAQUS (Ref. 1) and the results are then imported to LMSVirtual.Lab (Ref. 2) for further acoustic computations. As the main focus of this work is on the acoustic computations, only a brief description of the process involved in the structural vibration calculations is provided. In the present work, the “Horn effect” is inherently captured in the acoustic simulations. Two model tyres, viz., with tread pattern and with circumferential grooves is evaluated. The presence of tread leads to the phenomenon of stick slip and stick snap mechanisms contributing to the overall tyre noise. In addition, the motion of air through the grooves causes air pumping noise. It is to be noted that the structural vibration computations were performed on a rotating tyre that translated on a stationary road. In other words, the tyre underwent rotational as well as translational displacement. The acoustic computations are however performed on a stationary tyre model. One of the challenges addressed in the present work is the conversion of transient vibration results on a stationary acoustic mesh. The surface accelerations, required as boundary conditions, are converted to the frequency domain by the Fast Fourier Transformation for the Harmonic computations. The details of the structural models as well as the acoustic models and a short description of the techniques used in the computations of the radiated noise are described in the next section

On the sound absorption coefficient of porous asphalt pavements for oblique incident sound waves

A rolling tyre will radiate noise in all directions. However, conventional measurement techniques for the sound absorption of surfaces only give the absorption coefficient for normal incidence. In this paper, a measurement technique is described with which it is possible to perform in situ sound absorption measurements for oblique incidence. The measurements are performed with a small microphone array, the 8p-probe, and the theory is based on the local plane wave assumption.\ud In this paper, an approach is proposed to determine whether a surface behaves as a locally reacting surface or a nonlocally reacting surface, which is an important characteristic for optimising asphalt pavements for noise reduction and for modelling techniques.\ud Measurements at various angles of incidence are performed to demonstrate this approach as well as measurements of the absorption coefficient at normal incidence to validate the 8p-probe with impedance tube measurements

Experimental review on interior tire-road noise models

Exterior and interior tire-road noise is a common problem for car and tire manufactures. Exterior tire-road noise is bounded by UN-ECE R117 and EC R661/2009. Interior tire-road noise on the other hand is determined by market requirements. Since the beginning of the last century different model approaches on exterior and interior tire-road noise have been reported. A brief review of these model approaches is given in order to distinguish which approach to model interior tire-road noise is most promising. Some experimental considerations are given as a guide line for this evaluation. The paper concludes that the most efficient model approach is a full interior tire-road noise consisting of a FEM/BEM exterior tire-road noise model combined with measured structure and air-borne transfer paths

Modelling and evaluating interior tire-road noise

Exterior and interior tire-road noise is a common problem for car and tire manufactures. Exterior tire-road noise is bounded by SPL limits mentioned on a vehicle pass-by as described in UN-ECE R117 and EC R661/2009. Interior tire-road noise on the other hand is determined by market requirements. Predicting interior tire-road noise and determining these market requirements are still very challenging. First a brief review of interior and exterior tire-road noise model approaches is given in order to distinguish which model approach for interior tire-road noise is most promising. Some experimental considerations are given as a guide line for this evaluation. A full FEM/BEM exterior tire-road noise model combined with measured structure and air-borne transfer paths appears to be most promising. By playing this simulated noise over head phone for a relative small jury one obtains an engineering tool where the tire-road parameters, for a specific car, can be optimised for to a comfortable interior sound field

"Doing" Reflexive Modernization in Pig Husbandry : the Hard Work of Changing the Course of a River

The Dutch animal production sector faces significant pressure for change. We discuss a project for the design of a sustainable husbandry system for pigs. Named after the Greek hero Hercules, the project aimed for structural changes in both animal and crop production. However, instead of changing the course of the river, the project ended up merely adapting its flow. The Hercules project ran into difficulties typical for projects aiming at reflexive modernization. It relapsed from an effort for reflexive modernization to ecological modernization, by ultimately leaving the structural features of the sociotechnical regime intact. We show how this resulted from the biases and limitations implied by existing institutions, in which the project was unavoidably embedded. We introduce the idea of reflexive design, as "doing" reflexive modernization, which implies working on action and structure at the same time. A number of recommendations are given for reflexive design projects like this