I’ve been wondering about that, too. Gravitational waves are, as the narrator said, “ripples in the fabric of space-time.” They are waves, but they are not electromagnetic waves. They are not light. There is no electrical or magnetic component in a gravitational wave.
Sound can’t move in a vacuum and gravitational waves can’t move in a true vacuum either. But space-time is not a true vacuum. There is a fabric in space and time and gravitational waves make ripples in it as they propagate outward, just as sound makes ripples/waves in air or water, or whatever medium it’s moving through, as it moves outward.
So gravitational waves are much more sound-like than light-like, and they say we “hear” it rather than see it.
Well, that’s just the explanation I came up with in my confused little head to explain to my own satisfaction what the physicists were ‘splaining to us. No idea, really, if it is correct. If it is, the next question is, are these gravitational waves longitudinal in nature (as sound waves are) or transverse (as ripples on a pond are). Keeping with the sound analogy, I’m guessing they are longitudinal.
Of course if they could build a gravitational interferometer, we could detect the UFOs entering the influence of the planet.