there was tour being given in a rubber products factory.

The guide pointed at a machine that was going "thump-whoosh, thump-whoosh, thump-whoosh"
"This machine makes rubber baby-bottle nipples", said the guide.
"What is that strange sound?", asked a tourist.
"Well, the 'thump' is the locking of the mandril around which the nipple is formed, and the 'whoosh' is a set of needles on a spindle firing up to poke the holes in the tip of the nipple."

so, they go on and come to a machine going "thump, thump, thump, thump...whoosh"

"This machine makes condoms." said the guide.

"The sound is different", says the tourist

"Yes, the 'thump' is the locking of the mandril where the machine recieves warm latex which is then cooled quickly to form the condom."

"But...there's a 'whoosh' here too sometimes..." wonders the tourist.

"Well, every fifth one, a set of needles pops up and pokes holes in the tip."...admits the guide.

"Oh! I'd think that would be bad for the condom business!"

"Yes...but it sure is good for the nipple business!"