Process for producing tyres capable of reducing cavity noise and set of tyres obtained thereby

A process for producing tyres, comprising:

• arranging a plurality N of sets of noise-reducing elements, wherein all the noise-reducing elements belonging to each set have a respective substantially equal dimension Lx, with x ranging from 1 to N, the respective dimension Lx of the noise-reducing elements of each set differs from the respective dimension Lx of the noise-reducing elements of the other N−1 sets, and the plurality N of sets comprises no more than four sets;
• feeding in succession a set of tyres for wheels of vehicles, wherein each tyre has a respective inner circumferential extension, and the set of tyres has different values of the inner circumferential extension;
• for each one of the inner circumferential extension values, determining a respective number nx of noise-reducing elements for each set of noise-reducing elements, with x ranging from 1 to N, as a function of the value of the inner circumferential extension, wherein for at least one value of the inner circumferential extension of the set of tyres, at least two respective numbers nx differ from 0;
• and
• for each tyre of the set of tyres, collecting from each set of noise-reducing elements the respective number nx of noise-reducing elements determined for the value of the inner circumferential extension of each tyre and applying the collected noise-reducing elements in a circumferential sequence along an inner surface of each tyre, with the respective dimension Lx oriented circumferentially.