It sounds like your Surf PI Pro works exactly like mine does. I hear the same sounds. I read the manual and found that it is only a guide for how to set the machine. Different conditions require different settings. There are many people who have different methods to tune this detector, and none of them work so well for me except the way I discovered.
You will find that you have only 2 controls to fiddle with on the Surf PI pro. This means you can experiment with the 2 knobs until you find the setting that works best for you. Keep in mind the best setting will change depending on the ground, and how deep the coil is submerged. So it is good to adjust the detector in the exact condition where you will be using it.
What I do is to take a sample target like I am hunting for and bury it where I am hunting. Then I set the tuner knob to 10% and adjust the gain control to different settings while sweeping over the target for the best signal that is easiest to recognize. Take notes what gain level the best signal is found, then set the tuner to 20% and repeat the process. Repeat again with tuner at 30%, 40% and upward to 100% until you find what setting gives you the best signal to find your target. Use this setting for hunting. But if you go to where the hunting conditions are changed, then start over with the procedure to find the best signal. The process of adjusting the controls takes about a minute. Be sure to tie a string to any jewelry you bury for a target, just in case.
If you are wanting to discriminate to avoid trash targets, the method becomes a little more involved. You bury 2 targets apart from each other and sweep over each of them while making notes of which settings you get the best signal, and also which settings allow you to identify which is the trash more easily. Then you use both these settings when you hunt. After locating a target, then switch to the best discriminate setting to see if you can identify trash.
I caution against using discrimination, because I have found some gold that can't be distinguished from a lead fishing weight or a nickel with the Surf PI Pro. This is why I dig everything at the beach and throw out the trash. Ans I use the simple method of burying a single target to set the controls. I usually adjust to keep a very weak hum noise in the headphones for maximum depth in finding a target. I don't like dead silence, cause it gives me the feeling I am missing treasure. I found it is good to toss a coin in the sand and sweep over it occasionally so you can hear the sound of the target and recognize how it is different than the SAT noise and other false signals, and to reassure yourself that the coil is working to find treasure.
My method is not recommended in any manual or by anybody except me, but it sure works good for my Surf Pi Pro. And for the money, the PI Pro goes pretty deep and can find a lot of fun treasures if you don't mind diggin' the trash.
Hope that helps, happy huntin'
