A method and installation for inspecting a butt weld of transverse ends of metal strips held together between first and second jaws along the ends, include leaving an interstice between the jaws for passage of a first transmission channel of incident waves generating ultrasound waves on one surface of the first strip and enabling passage of a second transmission channel of waves emerging from the surface of the second strip. The incident waves of the first channel are generated using laser pulses in an operating state implementing a third channel of waves generated on the surface of the first strip, passing through the weld, and emerging in the second channel. Weld inspection characteristics are identified by analyzing the operating state related to the pulses and a measurement of a signature of a vibration state of the surface of the second strip upon emergence of the waves in the second channel.