Sound in water main

So I go to the basement and hear noise where my water main enters the house. It sounds as though a faucet is on and water is being used, BUT all my faucets are closed. I go over and notice the water meter is not turning. SO I don't think much about it - since I am not being charged for the water noise I am hearing.

Someone then told me that it could be a water leak outside my house. My wife and I did notice a slight drop of water pressure a long time ago, but not so much that I made a big fuss about it (and I generally like high water pressures when I shower). Is this something I need to worry about?

Thanks

Is there an area where the grass is always green, or the soil soggy? Sound can travel down the pipe making location of a leak tougher. Are you close to a pumping station? If the meter isn't registering any use, if it isn't transmitted noise, it may not be a problem. It could be a very small leak. Note the meter reading, then let it sit for a couple of hours, or preferably overnight, or while you are away at work, then check. Toilet flapper valves are notorious for slow leaks when they get old, and the filler valve opens to refill the tank to the proper level. You could try turning the supply to the toilets off, then monitor the tank level to see if it drops, or the noise stops. The last thing I can think of is if there is a check valve in the meter and you don't have an expansion tank on the WH. When the WH runs, it expands the water, which can cause the pressure to rise...if the check valve isn't sealing perfectly, it can make some noise as the water pressure is equalized.