Two black holes merge, and a good few percent of their total mass is converted into gravitational radiation.
Years or decades later, the resulting gravity wave passes through nearby stars. Does it have any observable effect on the light emitted by those stars while they are being "chirped"? If so, at what distance would that effect be observable? The star's solar system only? Light-years? From a nearby galaxy, or even a distant one? My gut feeling is that if any effect exists, it will be detectable only quite locally, but I really have no idea what the effect, if any, would be.