Possible causes for sound of water running through house pipes when water is off?

We recently moved back into our beach house after hurricane Sandy. During the storm repair the lower level was rebuilt including moving a bathroom and moving the house valve (only a few feet). We always now hear the sound of water running through pipes (a whooshing sound)even though no water is running. Here is the strange part. When I shut the house walve ( this is inside the house where the water line enters the house which is in the wall behind a panel)the pitch of the sound changes slightly but it does not go away. One would think if there was a leak after the valve the sound would stop. In addition when we run water in the house we hear the usual sound of water running in the pipes layered on top of the first sound. The pitch of the first sound does not change. The plumber is stumped as am I. When could possible cause this? It’s pretty annoying.