Abstract: The technical field of the invention is that of searching for or analyzing materials, in particular liquids, by optical means. The method of optically measuring the transparency of a liquid uses a turbidity analyzer comprising at least one emitter of light passing through an optical interface piece providing an interface with the liquid illuminated in this way, and at least one measurement cell receiving a fraction of said light via a second optical interface piece, said fraction having traveled a given distance through said liquid. According to the method of the invention: ultrasound waves are generated in the vicinity of the emitting and receiving optical/liquid interfaces of said optical pieces in contact with said liquid; gaseous microcavities are thus created in the liquid and said interface surfaces are cleaned when said microcavities implode; and the emission of said ultrasound waves is stopped and the light received by the cell is measured.