A friend of mine [named Tom Yuval] went to buy a tuning fork. He explains that nearly all tuning forks are 415, 440 or 442 Hz. 440Hz would be the standard and the most popular one or something.
When he finished, he got a 442Hz fork and a gift from the salesman. "This is for you to remember our service, and also you got additional 2Hz for the price of 440Hz one", he said. [End of story]
(442 is said to be a different standard, allegedly used for tuning orchestras because some sound-producing devices are problematic with low frequencies so they raise the whole thing a little up. Which doesn't matter, at least not as much as the relative frequency ratios between such devices.)
P.S. Someone please remind me the source of this Russian quote (a real one), about an experimental physicist getting visited by a KGB agent:
- what is this part?
- it's a transformer.
- what is it doing?
- it decreases the voltage.