I'm particularly intrigued by why the range would impact the sound based based sensing? Is it because of spacetime curvature or something?
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.
He went to a lot of effort to try to come up with a plausible description of what "life" would be like in such an environment. That fired my imagination also, and I wondered how we could do such a thing in a scientific manner. Given the rules of the Standard Model, in principle almost all aspects of the surface conditions could be elucidated, but I feel we would be missing almost all of the essence of it. Just like a deep understanding of Quantum Electrodynamics won't help you determine from first-principles that Earth has pretty sunsets or that your hair stands up if you take a wool jumper off.
For example, the surface of a neutron star would be very bright in gamma rays, but those are subject to pair-production in the strong magnetic field of the star, making light effectively a short range sensory mechanism. Meanwhile, the enormous density of the crust means that it transmits sound incredibly well and at enormous speeds[2], making acoustics the equivalent of our photon-based vision sense! But it would hemispherical at short range and 2D in a complicated way at long range. Spacetime itself would be strongly polarized, atoms would be distorted into spindles and have strongly anisotropic behaviour, general relativistic effects could be felt in everyday scenarios, and there are likely dozens of other effects the we can't even fathom by merely staring at a handful of field equations that we developed in our comparatively cold, flat spacetime.
1] https://en.wikipedia.org/wiki/Dragon%27s_Egg
2] The speed of sound in Neutron stars is just under 0.578 times the speed of light! https://physics.stackexchange.com/questions/54684/is-the-spe...