The coil noise is two possible things.
1. Coil strike - you are hitting something which can cause a vibration through the coil. Check the lead is connected correctly to the detector, you are looking for loose connections. This does happen quite a lot - the coils are very sensitive.
2. You will always get electro static discharge as you are rubbing a plastic coil along the ground and it will build up. This is nothing to worry about and yes it can make you stop in your tracks. You will also get EMI (check the manual how to control this) Also power lines, electric fences etc etc.
Ground noise - if you are using a mono on the 4500 they are still susceptible to ground noise, pockets of hot ground, red clays and the like. If big enough, you will also be hearing hot rocks. The difference? Ground noise will not usually be an even response both ways on your swing. If in doubt - dig. Dig a round scrape about the same size as the coil - don't lower the coil in the hole but keep it level with the ground. If the response is the same or moved to one side, its probably ground noise. You will get used to ground noise/hot ground and yes, it takes some time getting used to. I use a 4500 and I swear that some ground noises are a sweet sound and then gone.
Lead is a good sign - gold sounds very similar. It is a good thing to ground balance regularly and with the quick balance button, it is now very quick. Remember, the ground type can change quickly so if the 4500 even gets a little bit cranky - GB it.
You may need to play with the 4500s settings if it gets too noisy. If you are using a mono, switch over to a DD for a while. There is no magic settings as all ground is different- check the manual against the coil type.
The sound of gold - you cannot miss it - depending on your settings, you should get a high -low sound on your sweep. The first sound I get I first off wipe the suspect area with my boot - if its gone, I move on. If its still there I take another swipe into the first layer of soil/loam. Gone? Move on. If its in the hard compact ground - dig it. Yes, you will miss buttons etc but you will spend a lot more time actually swinging. These rules dont apply to mullock heaps as the throw outs could actually be close to the surface.
No two detectors will sound the same and it will take time to get to know your 4500. Good luck.