Process for generating a homogeneous gas mixture of o-xylene and air for the production for the production of phthalic anhydride wherein o-xylene is completely evaporated in the absence of oxygen, superheated and then mixed with air and supplied to a phthalic anhydride reactor. The vagus nerve stimulation and carotid baroreceptor stimulation therapies may be provided using a single implantable pulse generator, which can coordinate delivery of the therapies. The invention describes formulae of the voltage to be applied to the separate loudspeakers of the loudspeaker column, which makes it possible to realize the constant coverage angle over the entire frequency range and to suppress the side lobes to a far-reaching extent.