Someone pinpoint what this sound is?

No load on the engine(not the hissing sound):
http://www.youtube.com/watch?v=OIxyrKjpat0

A/C on(pecking noise is now very noticeable):
http://www.youtube.com/watch?v=xWhknpjegb8

A/C on and in gear(pecking noise is bad):
http://www.youtube.com/watch?v=o8vqH3-qsxM

As you can see it has a 2.4, has 165k miles on it. Only does it once the car is running at normal temps but runs and sounds good while driving, it just sounds like that at idle.

Sounds like valve noise. Try changing the oil and filter, see what that does.

Is the sound only occurring when the A/C is turned on?

Oh the memories. My old 2.4 did the exact same thing. I took it to the dealer, and they said it was normal for that engine. I called BS on that reply, but spoke to quite a few other 2.4 owners, and they had the same noise.
I did a screw driver hearing test on the whole engine, and it seemed like the noise was coming from the fuel rail.
I traded the car in soon after...so never did find out what it was. I know this much...The car was hard as hell on gas.

the car only sounds bad when the A/C is on or in gear. As you can hear it sounds worse with both A/C on and in gear. So is this normal for these engines? The oil and filter get changed every 3-4k and is due here soon. I tried putting premium gas in the car but it doesn't sound any better.

Dude...I'm not sure. I took my car to the dealer, and they said it was normal.
I contacted many 2.4 owners... and they were having the same problem.
The noise on my car was coming from the fuel rail. But always bothered me.
I never did get it resolved. Not to mention how bad the engine ran with AC on. Over heating was also a problem in summer mothes. I'd take it to a reputable mechanic in your area. (not a dealer) Have him/her do a sound test on the engine. .