Nope, radio is not likely to work or not for very long. Best chance of anything like that working is hooked to a motion detector, so it comes on just when they are moving around. Makes it harder for them to get used to.
But really the only option is fencing. You can get deer netting or plastic fencing in rolls pretty cheap.
Raccoons LURV corn and will not leave you any. But honestly, when I used to live on 5 acres and had plenty of room to grow corn, I gave up on it. EVERYBODY loves corn - deer, raccoons, groundhogs, opossums, squirrels, birds, mice, etc . And we had all of those on our property. I think I would have had to grow it inside a bank vault! (And then I'm not sure the raccoons wouldn't figure out the combination locks!