Seal for motor vehicle opening frame

Seal for the surround of an opening in motor vehicle bodywork, this seal comprising a first section piece (1) forming a clip of U-shaped cross section, made of elastomer or of plastomer, capable of sitting over and gripping a projecting part of the surround, and a second section piece (5) made of an elastically deformable flexible material, this second section piece abutting the outside of the base or of one of the branches of the first section piece and forming, by itself or with the part of the first section piece that it abuts, a tubular member, at least one orifice (6) placing the inside and the outside of this second section piece in communication, this second section piece being intended to be compressed by the opening leaf associated with the opening in the bodywork, when this opening leaf is in the closed position, so as to seal at the surround, this seal being characterized in that, housed inside the second section piece (5) is a third section piece (7, 10, 11) made of an elastically deformable flexible material which may or may not abut the first section piece (1) or the second section piece (5) and which forms, by itself or with the part of the first and/or second section piece that it abuts, a sealed tubular member connected to a source of fluid under pressure and capable, under the urging of this fluid, of coming into contact with the interior face of the second section piece (5) in which it is housed in order to improve the sealing and soundproofing properties of the seal when the vehicle is moving at high speed.