On Mon, 12 Oct 2009 20:01:40 -0600, "SteveB"
wrote:

I was taking a shower, when the water started a chattering noise, and the
spray was a pulsed spray. This came on when the Moen twist dial was in the
same position for about two minutes. I changed the dial, then returned it
to the original temperature position, and it did it again. A little
adjustment of the dial makes it go away, but it returns. What's this?

Steve



The flow of water is the same Hz (or multiple of) the natural
frequency of the piping. Try slightly decreasing (or increasing) the
flow rate through the pipes to stop the noise.