Reducing noise level from tyres - lining interior with foam of specified youngs modulus density and thickness range

摘要

A tyre has a sound-reducing layer of open-cell foam on part or all of its internal surface. The inside of the tread and/or of the sidewalls has foam with E-modulus less than 5 x 10 power 5 N/sq. m (measured dynamically) at -20 deg. + 80 deg. C, density at least 35 kg/cu. cm, air resistance of 50-300 Rayl/cm (5 x 10 power 5 - 3 x 10 power 4 Ns/m4), and at least 15 mm thick. The chemical compsn. of the foam is not critical; a suitable material is polyurethane, it can be applied separately to the inner tyre surface or foamed in situ. The system is effective with tubeless or inner tubed tyres. Construction reduces noise of movement and hence total vehicle noise without being expensive or heavy or affecting tyre properties, is esp. effective in the physiologically important frequency range of 500-2,500 Hz.