All of a sudden when I turn off either hot or cold water spigot quickly, I hear the pipe rattling under the floor. This happens everyone - bath, kitchen, washer.

I suspect that a hanger may have come loose - easy to fix. Bit the big question is how to prevent the force of the water shutting off to avoid the sudden pressure opening a leak in a weak connection.

I know I can install an air volume pipe or tank above the line to reduce the sudden pressure. But I'm wondering if maybe the water line pressure coming into the house might be too high. What's the nominal city water pressure range? And, if I install a pressure reducer, the ones I have seen only reduce the pressure after a valve is opened -- the pressure in the line when all valves are closed is the same as the upstream line pressure.

Does any of this make any sense?

Thanks in advance.

You may have an existing bad pressure reducer. Vibrating pipes is characteristic of that.