Wearing ring!
That my friend is the distinct sound of a wearing ring that went "south" on you. Although, there is a slight possibility you have something caught in your suction side pump end, it's normally the wearing ring.
If you can get under it and look into the intake grate with a flashlight, look at the casing area around the impeller. This is where your wearing ring is. It should look like a dark color, super hard rubber material. The clearance between the impeller and the wearing ring is less than 1/16". So if you see obvious damage or a great distance between the impeller and casing, it's time to pull the pump and do a wear ring replacement!.........Sometime, when the liner lets go, it folds up into the impeller.....but see if you can check it and get back with us. Look on the bottom left of your post page and you'll see links to other posts that will give you more insight into this subject.