Ulf Sandberg - Swedish National Road and Transport Research Institute, Sweden
Yasuo Oshino - Japan Automobile Research Institute, Japan
[14:20-15:20] Room: Room F
We4.F.1 A CLOSER LOOK AT THE TREAD GROOVE RESONANCE IN TYRE/ROAD NOISE
1Swedish National Road and Transport Research Institute, Sweden, 2Chalmers University of Technology, Department of Applied Acoustics, Sweden
It is widely recognized that most modern tyres display a prominent peak in their noise emission frequency spectra around 1 kHz. Since tyre/road noise is a major part of road traffic noise, this effect is also substantial in road traffic noise. One of many potential causes for this peak is the so-called pipe resonance formed in grooves in the tread pattern. Many tyres have in their tread patterns longitudinal grooves that more or less effectively form a pipe in the tyre/road interface, which is believed to cause noise emission at its resonance frequency, usually around 800-1200 Hz. Most tyres also have grooves that are lateral or diagonal to the rolling direction, some of them open at both ends, some closed at the inner end. Thus one will have both half- and quarter-wavelength resonances. The theoretical frequency of this phenomenon can be calculated based on the theories for musical instruments with pipes. Such calculations may include corrections for non-perfect shape of the pipes in relation to a perfect and narrow cylinder. The paper describes and examines the possibility of pipe resonances in tyre tread grooves, and presents calculations for the resonance frequency of various groove types. A brief literature review is presented. It also discusses how such groove resonances may be present in current tyre tread patterns and potential ways to reduce them. It is concluded that more research on this subject is motivated; in particular to examine the Q factor of the resonance for a realistic airflow through the grooves.
We4.F.2 PREDICTION OF TIRE PATTERN NOISE
Jeong-Guon Ih1, Sung-Hwan Shin1, Eun-Bae Kim1, Won-Sik Choo2, Gi-Jeon Kim2
1Center for Noise and Vibration Control, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Korea, 2Kumho Tire Co., Korea
Pattern noise radiated from tires is very important in the sound quality of pass-by noise as well as the interior noise of a car. It is known that the impact force at leading edge of tire is the main cause of the pattern noise. In this study, the prediction of tire pattern noise is attempted considering the impact at the leading edge of a tire and the subsequent sound radiation from the whole tire surface. First, the normal pressure at the leading edge between tread block and flat road is measured in both static and dynamic load conditions. From measured data, the pressure distribution function of width direction at contact edge and the impact force variation of circumferential direction are obtained. Second, the Hertzian contact theory is employed to approximately calculate the maximum force magnitude and impact duration time at variable speeds. Finally, the transfer function between the impact tread and the sound field is convoluted to the obtained impact force for the prediction of radiated overall pattern noise. Predicted pattern noises are compared with measured exterior and interior noises of a car driven by the chassis dynamometer in a semi-anechoic chamber, which reveal that the spectra of these noises agree reasonably well.
We4.F.3 ANNOYANCE MEASURED INSIDE VEHICLES PASSING THROUGH DIFFERENT ASPHALT PAVEMENTS
Gaetano Licitra1, Gianni Amadasi2, Mauro Cerchiai1, Paolo Vanzo2
1ARPAT- Environmental Protection Agency of Tuscany - Deptartment of Pisa, Italy, 2S.C.S. Controlli e Sistemi s.r.l. - Campodarsego - Padova - Italy, Italy
During the last 3 years a test using two experimental type of pavements was carried out over an Italian motorway near Pisa. The trial will compare the durability and performance of a traditional thin porous layer (about 40 mm) with that of a double draining layer. The latter is composed of a 40 mm thick upper layer (grading 0/18) and a 25 mm thick top layer (grading 0/10). Some measurement campaigns were carried out to study the time degradation of the acoustical characteristics of the pavements such as noise measured outside the motorway, inside vehicles and the absorption coefficient. Moreover some psycho-acoustic parameters (loudness, roughness, prominence) were measured inside different type of cars. These were carried out together with the usual noise spectral analysis and Leq(A) measurements. The objective was to obtain information about annoyance or noise measured outside the road infrastructure using measurements carried out inside a vehicle passing on it. The measurement were extended to a motorway section 12 km long having some different pavement types in order to collect information about the annoyance given by pavements other than those previously tested, using both some simply-to-measure parameters (short Leq(A), spectral analysis) and more complex parameters such as loudness, roughness and prominence that are used to link the human judgment on the status of the asphalt to the human perception. The results matched each other especially for spectral data (absorption peaks) and hourly Leq(A) estimation, so giving some important indications about noise emitted from the motorway infrastructure about its tonal components and sound levels.