What are the alternatives for sound proofing?

The Safrane's design was a deliberate effort to overcome the 25's main weaknesses - insufficient chassis stiffness and poor build quality. Renault was also keen to take noise reduction to best-in-class levels. These constraints resulted in a much heavier car than its predecessor (+200-300 kg / 440-660 lb.) due to a heavily reinforced chassis and the liberal use of sound-proofing materials.