That, and the high frequency. For example, the Earth orbiting the Sun produces gravitational waves at a frequency that's about (factors of 2 and pi here and th

That, and the high frequency. For example, the Earth orbiting the Sun produces gravitational waves at a frequency that's about (factors of 2 and pi here and there) the orbital frequency; order of 1e-8 Hz. The black holes were producing 250Hz waves if I read the article right.