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A conceptual framework has been developed for investigating the generation of sound by tires. Recent measurements have quantified some of the characteristics of truck tire sounds. The characteristics that have been measured include the peak A-weighted sound level and its dependence on the tread pattern, speed, and deflection of the tire; the effect of the road surface on tire sound levels; and the spectral distribution of tire sounds. These characteristics are discussed in terms of the mechanisms of tire sound generation.

A technique has been developed to determine which tire nonuniformities are responsible for tire roughness. The measurement and interpretation of high-speed uniformity and instrumented vehicle data is discussed. The results presented emphasize the necessity of viewing the tire and the vehicle as a dynamically coupled system rather than as two separate and distinct components.

This paper discusses the importance of the spectral distribution of the energy in the sound to the dB(A) level of the usual passby test. A described technique obtains reproducible “real-time” spectra from the nonstationary sound field. Doppler effect and source frequency shift are quantified in relating these spectra to the tread pattern repetitions. Inverse square law fitting is viewed through the two-source-microphone relation which changes during the spectral window period. Spectra are shown for 6, 12, and 50 ft (1.83, 3.66, and 15.2 m) passby microphones and for a microphone carried on the truck.

Pavement texture has a pronounced effect on what is commonly referred to as simply “tire noise”. The disturbance in question should properly be called tire/pavement interaction noise. A noise ranking can be made among tires only when they are all measured on the identical pavement texture. The importance of pavement texture is most clearly apparent with smooth and rib tires. Highly textured surfaces cause the noise level of conventional rib truck tires to reach that of lug tires. Passenger tire noise rankings are reversed by pavement texture differences. The gradient of pavement texture, both lateral and longitudinal, is a definite problem affecting the reliability of passby noise measurements.

This paper presents data for several tire/pavement interaction noise measurement problems present in passby tests. Two of these, the after peak and the difference of the passby maxima with direction of travel, have not been previously reported. The underlying causes of many of the problems are discussed. Probable interactions with current regulatory procedures on the overall vehicle passby levels are indicated. The need for much more precise site control is pointed out, especially with respect to atmospheric conditions which strongly affect the noise transmission path and with respect to the pavement texture.

New materials and advanced car designs have increased the needs for tire testing facilities that can accomplish indoor evaluation of tire properties and performance. The new dynamics machine discussed here has been used successfully to measure forces exerted by loads, speeds, and other operating characteristics. This new road wheel test shows the sensitivity of the dynamics machine to tire properties depending on cornering response. The machine is economical and practical and extremely versatile, permitting many new tests that contribute to the application of new tire design concepts.