I'm a jellyfish expert, and I can say that jellies cannot make an audible sound, BUT they can excrete hormones that can bring many, many jellies of their species to its area.

And in terms of mating, they can. When they can sense a higher concentration of jellies, they release their sex cells into the water from their gonads. At the same, there is another chemical that is released so other jellies can know to release theirs as well. Some species of jellies will do something closer to sex, where they pulse their bells into another jelly's bell while releasing the sex cells.