After identifying the noisiest spots on the 143 km of elevated segments (metro, RER, tramway, and Orlyval), we were able to take the following corrective measures:

• Replace line M5 rolling stock with soundproofed wheels

• Apply acoustic insulation to facades

• Install acoustic panels

Our goal: eliminate all noisy hot spots by 2020!

Each time rolling stock is modernised or transferred from one line to another, we strengthen our acoustic requirements for interior and exterior noise levels. Our target is to reduce noise levels by 2 to 3 decibels dB(A). Failing that, we quantify the impact to identify preventive solutions, in order to avoid making the initial situation any worse.

Rolling noise is the sound created when the wheels make contact with the pavement or track. It can be reduced by optimising infrastructure and rolling stock maintenance:

• Reducing rail and/or wheel roughness, and/or increasing the energy dissipation in tracks for train rolling stock

• Reducing the surface irregularities of tyres and the traction surface for rolling stock fitted with pneumatic tyres

To eliminate squealing brakes, we have adapted our equipment.

Wooden brake shoes, which do not squeal during braking, were maintained on the trains on metro lines M6, M10, M11 and M12. Some squealing is audible on trains fitted with composite braking systems (metro lines M1, M4 and M14; latest generation metro trains and RER trains). With our manufacturers, we are searching for satisfactory solutions for this equipment: modification of brake pad fixations, new pad specifications, or switching to electrical instead of mechanical braking systems.