Nebulising device having an elongated general shape, of the ultrasonic wave acoustic concentrator type, capable of generating a liquid droplet spray from a liquid, including; - an ultrasonic acoustic concentrator nozzle provided with at least one liquid intake orifice and at least one liquid discharge orifice, and on the opposite side of said discharge orifice a piezoelectric element suitable for emitting acoustic waves in said liquid, and the cross-section of said nozzle exhibiting progressive narrowing in the direction of said at least one discharge orifice, such that in said nozzle the acoustic waves are focused to create said spray of droplets of said liquid; - a pump or "circulation pump" connected to said nozzle by the at least one intake orifice created in said nozzle, said circulation pump being suitable for generating in said nozzle a sufficient liquid pressure to maintain a liquid jet outflowing via said discharge orifice of the nozzle; said device being characterised in that it includes - a lower frame of elongated shape, including a tank module and a nozzle module, said tank module including a tank, - an electronic unit of elongated shape, situated in the projection and preferably in the axis of said lower frame and optionally being integral therewith or being detachable therefrom, said electronic unit including a cover, - an upper part including a spray discharge tube and ventilation means suitable for generating an air flow via said spray discharge tube; - optionally ventilation means for creating an air flow carrying said droplet spray via said spray discharge tube outside said device; wherein: - the nozzle module comprises said nozzle, - said pump is connected on one hand to the tank and on the other to said nozzle; - the upper part is arranged above the lower frame such that the rear part of said spray discharge tube is situated at least partially inside the tank module, and the spray discharge tube is projected towards the front of the device. - an ultrasonic acoustic concentrator nozzle provided with at least one liquid intake orifice and at least one liquid discharge orifice, and on the opposite side of said discharge orifice a piezoelectric element suitable for emitting acoustic waves in said liquid, and the cross-section of said nozzle exhibiting progressive narrowing in the direction of said at least one discharge orifice, such that in said nozzle the acoustic waves are focused to create said spray of droplets of said liquid; - a pump or "circulation pump" connected to said nozzle by the at least one intake orifice created in said nozzle, said circulation pump being suitable for generating in said nozzle a sufficient liquid pressure to maintain a liquid jet outflowing via said discharge orifice of the nozzle; - a lower frame of elongated shape, including a tank module and a nozzle module, said tank module including a tank, - an electronic unit of elongated shape, situated in the projection and preferably in the axis of said lower frame and optionally being integral therewith or being detachable therefrom, said electronic unit including a cover, - an upper part including a spray discharge tube and ventilation means suitable for generating an air flow via said spray discharge tube; - optionally ventilation means for creating an air flow carrying said droplet spray via said spray discharge tube outside said device; - the nozzle module comprises said nozzle, - said pump is connected on one hand to the tank and on the other to said nozzle; - the upper part is arranged above the lower frame such that the rear part of said spray discharge tube is situated at least partially inside the tank module, and the spray discharge tube is projected towards the front of the device.