As long as we're asking plumbing noise questions, I'll ask one that I've never managed to find a satisfactory answer to. When I turn on the hot water, such as

As long as we're asking plumbing noise questions, I'll ask one that I've never managed to find a satisfactory answer to. When I turn on the hot water, such as in a tub or a sink, some cold water comes out before hot water does. (I have to wait for the water to "get hot", which of course is not really getting hot, it's flushing cold water out.) I'm pretty sure I'm not imagining this, but I can hear when the water is hot. The only way I know how to describe it is that it sounds a bit calmer. Why is that?