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The A-weighted sound level accounts for the bulk (but not all) of the jury's reaction to the sound of trucks coasting on a variety of tires. A component of the jury's reaction is related by the study to the manner in which the sound decays after the vehicle passes the point of observation. This component also appears to depend strongly on the characteristics of the sound. The jury's reaction shows two forms of distortion: end-of-scale compression and temporal drift. The analysis attempts to account for these factors and to see beyond them into the jury's basis for reacting.

As highway development programs brought increased truck traffic through formerly isolated communities, public sensitivity to truck tire noise increased significantly. Industry was alert to the possible consequences of social and legal pressures and acted in concert to set up standards for noise control and for establishing criteria by which to measure annoyance levels. Work by several leading associations provided a starting point for investigations by the SAE Truck Tire Noise Subcommittee. The Subcommittee's efforts resulted in formulation of a tire testing procedure and a consolidation of requirements to be incorporated into a proposed standard. This paper reviews the objectives and approaches of the Subcommittee and serves as an introduction to the accompanying papers.

This paper outlines the nature of the measuring equipment used in the investigation of tire-road interactions and presents the results of a study of the interfacial stress distributions of a radial-ply, a bias-belted, and a 4-ply bias-angle tire. There is a discussion of tractive ratios and effective coefficients of friction. Distributions of tractive ratios are displayed for all of the conditions treated and for the three types of tires. The paper also covers the changes in stress distributions that result from steering and the relation of these alterations to the lateral thrust and self-aligning torque of the tires.

The paper describes the enveloping properties of truck tires as consisting of two components of force, one in the vertical direction and another in the direction of travel. The responses to irregular surfaces are mathematically accountable in terms of the response to a step in pavement elevation. Tires may therefore be readily characterized through their reactions to step functions. Curves display the differences in enveloping properties available in the 10.00–20 size on the open market.

The forces generated by tires when traveling over irregular roads are related to the structure of the tire and to the geometry of the road surface in a useful mathematical relationship. Linearity and superposition principles allow an idealized and synthetic road irregularity to represent the response of a tire to realistic kinds of road irregularities. The association of the enveloping forces with factors related to the structure of tires facilitates the understanding of the enveloping responses. The analysis of the forces for the idealized road irregularity, coupled with the Fourier integral analysis of road surfaces, produces the spectrum of outputs for exciting modes of vibration in the tire itself and in vehicles.

There can be no control over environmental pollution without methods for measuring how the environment is being affected by mankind. Consequently, when traffic noise was identified in 1964 by communities as an important form of pollution, it became necessary to measure the amounts of noise present and to assign relative importances to various sources in vehicular traffic. Truck tires were identified as being significant contributors and engineers from the tire and truck manufacturing industries acting under the auspices of the SAE set about to develop a test procedure that satisfied the immediate need - to initiate control over truck tire noise. This paper is a review of the outcome of that effort by one who participated in the earlier work on the testing standard. How well the method works, and how well it serves to meet the objectives now on the horizon are the preliminary topics of this discussion.

This presentation is a sequel to Paper 762035 in that an alternate method of testing for tire noise is investigated and the results of experimental studies are described. The alternate method is designed so as to preserve in the proposed measurements, the pertinence of J57a. Comparative testing of numerous tire designs in the two manners shows that this objective has indeed been accomplished. Rather than presenting the experimental details behind each of the various foundations for the proposed method, this paper confines its discussion to the items significant to the description of the method and to a comparison with the J57a procedure.