What is this?

Guy visited a latex factory. During the tour, they entered a room where a bunch of machinces were boing "boom, sisssss, boom sisssss, boom, sisssss" The tour guide explained, in here, we are making baby bottle nipples. The boom is the machine forming the nipple, and the "sissss" is making the hole in the nipple.

They entered another room, where the machines were going "boom boom boom boom boom boom boom boom boom boom, sissss"

Guide says, "in here, we are making condoms............"

Buy says "I understand, but what is that "sisss" every so often?"

Guide says "The boom is forming the condom, and the "sisss" is MAKING SURE THERE IS A MARKET FOR BABY BOTTLE NIPPLES!!"