An Unusual Occupation

I'm not sure if you would run into this in America, but apparently in Japan, if you go to a canned goods factory, one of those places that does vacuum packed canned foods, down near the end of the conveyor belts, you'll find a person doing something rather strange. He or she will be standing at a spot where all of the cans go by, with a metal wand in his or her hand, fairly loosely held. The wand they showed us had a wide grip, maybe an inch wide with rounded edges. It tapered down to a round tip, like a large ball bearing stuck on the end of the wand.   He or she will be tapping each and every one of the stream of cans moving along the conveyor belt once or twice with that wand. Occasionally, he or she will tap one, then pick it up and set it aside. What are these people doing?  Well, it turns out that a can with a good vacuum makes a nice musical ting when it is tapped. Bad cans make more of a dull clunk. So they are doing a quality check, basically.  On the show I was watching, they showed us that in a quiet room, with the experts tapping, the difference between a good can and a bad can is actually fairly noticeable. Of course, the experts are doing this standing at a factory conveyor belt with all of the other noises of the factory around them.  Can you imagine putting can tapping on your resume?