maybe there's a wind passing through the pipe that creates odd sounds. it may come from below or above your sink.

On the other hand we could say, "Maybe you have a happy faucett"....LOL

Having said that, let us now get down to the buisiness at hand.

From your description it is indicating that something is loose and causing a rapid change in the internal working pressure as the water flows through. The most common cause is a small piece of debris inside the faucett that is interfering with flow, or it could be a loose washer or spring.

Maybe it likes you?

So, an update finally. My contractor flushed out the line, per Rohl's recommendation, and that worked...for a while. Lately, my faucet has been singing again. Ugh. So I called Rohl, and they told me they redesigned the diverter, and will send it to me, and this should take care of the problem for good. Hopefully this new and improved diverter does the trick!