I had a similar posting a while back for my 96 EX. When I bought from my neighbor, I hadn't actually heard it run until he delivered it to my driveway. I thought it sounded a little loud... kind of like a diesel engine. Not sure if your noise is same. This is not a valve tap ( which is pretty loud on this engine anyway ) but more of a knock. I have convinced myself it is piston slap. The noise seems to come from the block, below/to the side of the exhaust. I did a low tech evaluation of the source using a shop vac hose to my ear.

The bad news is that this generation of Accords apparently had this problem and it is not a good thing. The good news is that it quiets down when the pistons expand and it is not a death sentence. Mine has been banging away for 20K miles and it hasn't gotten noticably worse.