Abstract
In snowy districts, motor cars are fitted with snow-tires, snow-spike-tires, anti-skid-chains to increase the adhesion between the tire treads and road surfaces. To get definite information of car noise under such condition, noise measurements were carried out on packed-snow roads and on snow-free asphalt roads. 1) Outdoor sound level pertaining to tested tire and chain shows a tendency to vary according to the vehicle speeds, which seems to be strengthened by the pattern noise. 2) Outdoor noise tests of three different tires show that the snow-tire characteristic, which affected strongly by the pattern noise, has clear peaks of S.P.L. (Sound Pressure Level) at low order fundamental frequencies. A more marked tendency is seen in the case of spike-tire. 3) Frequency analyses of outdoor noise when various chains are used show that S.P.L. is very high around 1 kHz, and the frequency characteristics seem to vary according to the forms and materials of the chains. 4) On the packed-snow road, the S.P.L. of outdoor noise decreased over all frequency range, in comparison with the outdoor noise on the snow-free road. The S.P.L. of indoor noise shows appreciable difference either on the packed-snow road or snow-free road.
