You need the burner orifice to match the type and pressure of fuel you're supplying the burner with. If you're using the high pressure LP orifice (which I believe comes stock from agri-supply), then yes, switching out the regulators to high pressure would solve the issue, but it would likely be cheaper to switch the orifice out. The benefit to low pressure is that it's usually cheaper and easier to add automation. The benefit to high pressure is a higher max BTU output. Even running low pressure you can get more than enough BTU's to bring 12 gal to a boil quickly.
Even using high pressure, that burner should run very quietly, so the fact that it doesn't sound like a jet engine isn't really telling you anything.
Edit: You might find this thread helpful-