A question of water and sound
 

Why is it that when you turn the hot water in tub on, as the water coming out heats up the pitch of the sound it makes rises? It's been that way in every house I've ever lived in. :confused:

If the answer is going to get technical, don't hesitate, I can handle it. Thx!

get ready for some relativity ;)

the relative size of the elastomer washer in the spigot changes with temperature; as the hot water heats the washer, it expands, pinches off the flow slightly which increases the water velocity which increases the pitch. Next time see if you can measure a slight reduction in water flow as the pitch increases and report back here.

BINGO... That is exactly what happens..well done

in some cases the shaft of the valve expands too.

For an Iron or even a brass(close enough) shaft the expansion rate is .0000063 per inch of shaft per degree rise in temperature from the norm.

So for a valve with a 1.75 inch long shaft (purty normal length) it will expand
.0017 inches. That is almost two thousandths of an inch (towards closed)

That would explain it. Thanks to both of you! :)

ahaha that is awesome, some people know way to much ...

awesome

Good supporting facts. To further put it into perspective, the coefficient of thermal expansion for nitrile rubber and neoprene are ten times higher than for steel and 6 times higher than for brass.