When I still had my hissers, I heard them hissing all of the time. The sound is pretty unusual and, when you aren't used to it, can be quite startling.
Hissers are very unique in the insect world for how they make their hissing sounds. The vast majority of insects manipulate their bodies in some way to make noise. A mosquito's buzz comes from the beating of its wings. Crickets chirp by rubbing parts of their wings together. Cicadas have a special concave membrane that they "pop" to make their characteristic noise. Other species rub against surroundings to produce a sound. Roaches are far more like us as they force air out of their spiracles (breathing holes), creating the hiss.You can often see this when they hiss, as the sound is so often accompanied by sudden contraction of the abdomen.
Source is Cornell University. Videos are from YouTube: one, two.