What did he say?
Okay, here goes.
The shape (volume, if you will) of space-time can change, usually due to mass. This causes phenomena like gravitation and (likely) inertia.
Now, not only space is affected by mass, but mass is naturally affected by the "form" of space - that's what gravity is all about, actually. The interaction of masses via the form of space-time continuum.
Okay, we've established that shape of space and time can change. Furthermore, the changes in it propagate through vacuum much like ripples in the surface of the water, and most likely at the speed of light.
Now comes the important part - theoretically, these propagations can be detected since they affect the shape of space-time, and thus affect gravitational fields slightly. Gravitation moves stuff around, thus gravitational waves move stuff around, so to say. Or more accurately, distortions of space cause distortions, tension and other stuff in objects that reside in the changing space.
Harmonic changes in space-time would make the objects in space oscillate.
Usually, gravitational waves caused by celestial bodies rotating each other are so long and weak by the time they reach us that it's really hard to detect the small changes, but it's obviously possible. If you want an example, here goes - tidal waves. The Moon orbiting Earth changes the time of tides in 27.5-day cycles. It is a real example of gravitational waves in effect.
More drastic changes in space-time could be easily detected. For example, should a large mass transmutate to radiation in very short time, or be dispersed to wide area, the change would propagate through space-time and affect everything on it's way. So theoretically speaking, let's put a 500 kg (250:250, obviously) matter - anti-matter bomb in space and you at a distance of, say, 100 km from it. The bomb goes off, 500 kg suddenly transmutes into gamma radiation and suddenly a relatively large mass is spreading away as massless fotons. This causes a tension in space-time to go off - not unlike pressing a large drum membrane down and then lifting your finger, which removes the tension and causes the membrane to "smooth out".
In space, the change is similar - but it happens in three space dimensions as opposed to only two of a more easily comprehendable membrane. The key point is that this relief of tension will cause a spreading change in the fabric of space, and that change will slightly affect things that it goes through. Strong enough, it'll splatter and crack everything in it's way. Weaker, it would perhaps be felt as a "whack" or something like that. And it would cause a mechanical shockwave in your ship/planet also, so that would be heard as well if it was strong enough. Even weaker, you could likely weakly hear it as a slight pop.
...mind you, 500 kg is a really small mass as far as gravity is concerned, but the energy of a 500kg anti-matter bomb is something I don't really want to think about.
The gravitational shockwave would be the absolute least of your worries at distance of 100 km... but assuming you were shielded enough to survive, the theoretical basis for "hearing" the explosion is valid, at least that's how I see it.
The same applies to swiftly disintegrating and dispersing a large concentration of mass (say, a space ship) from
small volume to
large volume, kinda like what explosions inside the ship would do. It wouldn't be as drastic as anti-matter bomb with full mass->energy conversion, but it would cause a small distortion. Most likely undetectable though.
Or, if the ship was using, say, singularity as part of it's generator (Minbari, anyone?), that going off would
definitely be heard/felt for a long distance.
