Underbody deflector with sound shielding properties

The deflector (1) has a rigid panel (2) and two deformable components (3) disposed on internal side of the panel. The deflector is arranged so as to permit the components to be compressed at a rate lower than or equal to 5 percentages once the deflector is mounted beneath a wall. The components are compressed as they have thickness greater than space between the panel and wall. The wall is beneath a body shell of a motor vehicle. An independent claim is also included for an acoustic protection system for a floor pan of a motor vehicle comprising a deflector and a wall beneath body shell.