A method of producing bubbles for treating a suspension by flotation, wherein in which the suspension enriched with dissolved gas is caused to flow into a flotation vat via a pipe the flow in the pipe is rapidly interrupted at a predetermined frequency by a shutter unit which is suddenly closed and produces, in the downstream portion of the pipe, a periodic wave of low pressure such that cavitation bubbles are produced in the flow in said downstream portion, the low pressure wave propagating in the pipe up to the flotation vat where it is reflected as a wave of high pressure which produces the collapse of the cavitation bubbles and forms micro-bubbles which become fixed to the particles to be floated, the conditions in the pipe being such that the micro-bubbles are in a super-saturated medium in relation to the local pressure conditions and tend to be enlarged during their flow up to the flotation vat.