The dark timbre of gravitational waves

Gravitational wave timbre, the relative amplitude and phase of the different harmonics, can change due to interactions with low-mass halos. We focus on binaries in the LISA range and find that the integrated lens effect of cold dark matter structures can be used to probe the existence of Mᵥ 10\, M_ halos if a single binary with eccentricity $e=0.3-0.6$ is detected with a signal-to-noise ratio 100-10⁴.