I would like to resurface this question. I put it on StackExchange a few months ago and I now believe I know the cause of my problem but can't seem to come up with a good solution.
I replaced the main water shutoff valve in my home last September. Since then whenever I run water anywhere in the house including sinks, showers or toilets I get a very loud whooshing in the supply lines while the water is running. This happens on both the hot and cold sides. I didn't have this before. One clue is that when I shut off the water at any faucet I can hear water continuing to run through the lines for another four or five seconds before the sound stops. It never varies. Another clue might be that when I replaced the main shutoff valve I was very careful to turn on the water at the curb very slowly so that I wouldn't slam the plumbing and cause a leak. I now believe the problem is with trapped air somewhere in the line coming into the house. However, opening the faucets and letting the water run hasn't solved the problem or made it better.
Someone on this site suggested that I might have an inverted U somewhere in the supply line that has trapped air in it. If so, could this have been caused by turning on the water at the curb too slowly and not flushing the air out of the inverted U? I think this may be the case because it would explain the whooshing and the delayed shut down due to the water pressure compressing the air in the inverted U section after I shut off the faucet. The supply lines are behind walls and mostly inaccessible so I can't visually verify this.
Assuming the above deductions are correct, could I possibly solve this by shutting off the water again at the curb - Then open all of the faucets inside and outside the house to prevent high pressure from slamming them and then opening the main valve at the street more quickly to flush any air out of the line?
I would appreciate any thoughts and suggestions.