I'm having trouble with custom attenuation curves. Can somebody help me invert attenuation so that the sound gets louder the further I get from the source please?

I have created an island and I’d like to create a sound source for waves. Ideally, as I understand it, this would be a single sound source in the centre of the island, but with attenuation applied in reverse so that full attenuation is applied at the centre of my ambient sound and starts appearing at the falloff distance. Ideally the sound would then become full volume outside of the falloff zone. Unfortunately, I don’t understand custom attenuation curves and I can’t seem to make any sense of what is going on with them. Am I on the right track? Can anybody point me in the right direction please?

Edit: I’ve created a solution by lining the shorelines with attenuation capsules rather than trying to use a sphere. My question above still stands, though, I think it would be ideal to have ocean noise in general attenuated in the middle of the island while having it play at full volume when swimming in the ocean, regardless of distance from the shoreline.

Edit: Found another solution using audio volumes, I think this might be the way to go.