A creature living on a neutron star might use sonar like we do light, because the speed of sound in the star crust is more then half the speed of light. In many ways it would be comparable. But the crust is only below the creature, not above. So its "sound sense" would only work for one hemisphere surround the creature, the other side would be silence, its equivalent of total darkness.

Neutron stars have thin crusts, possibly mere meters thick, and almost certainly with layers of some sort. Again, sound would probably travel at different speeds in the various layers, just like sonar does in oceans, where salinity affects propagation. There would be complex effects with distance to do with this. Locally, the sound could travel outwards in a hemisphere, but at long range it would likely be more 2D.

This is all speculation, but it's based on real science. My point is that we cannot really know, and no amount of staring at equations will help paint a realistic picture.