That’s precisely what LIGO measures, the gravitational waves from black hole mergers (or neutron star mergers, etc).
>Cosmic Heavyweights Collide – LIGO Detects Largest, Fastest-Spinning Black Holes Yet
https://scitechdaily.com/cosmic-heavyweights-collide-ligo-de...
>Cosmic Heavyweights Collide – LIGO Detects Largest, Fastest-Spinning Black Holes Yet
https://scitechdaily.com/cosmic-heavyweights-collide-ligo-de...