Spin 35.94% of maximum


Why 35.94%? In this case, we wanted to use a smaller spin value that reflects the fact that, in many models of the evolution of black hole spin during accretion, there is a magnetohydrodynamic coupling of the hole to accreting material. For rapid spin, the hole spins faster than the orbital frequency at the inner edge of an accretion disk; this coupling tends to slow down those holes. For slow spin, the disk spins faster than the hole; this coupling speeds up those holes. 35.94% of the maximum is a "magic" point at which the inner edge and the hole rotate at exactly the same rate! As such, it is a physically motivated choice for "slow" rotation in a model where a hole's spin evolution is driven by accretion.

In these sounds, the two GW polarizations are encoded via stereo: The "plus" polarization is in one ear, the "cross" is in the other. You can sometimes hear a cool evolution in the two polarizations, especially as the end is approached. Also, note that there are two angles describing the waves: Orbital plane and viewing angles. The orbital plane describes how the orbit is tilted with respect to the equator of the black hole (where the "equator" is 90° from the spin axis); the viewing angle describes the orientation of the system to our line of sight. Zero degrees viewing angle means that we are in the equatorial plane of the binary.

In all cases, the system's mass ratio is set to 10,000:1; the total mass was then adjusted so that it lies nicely in the band of the human ear. The total mass of the system turns out to be roughly 60 solar masses in this case.

Orbital plane 0°


0° viewing angle: iota_0_10000_4_0_00_h
30° viewing angle: iota_0_10000_4_0_30_h
60° viewing angle: iota_0_10000_4_0_60_h
90° viewing angle: iota_0_10000_4_0_90_h

Orbital plane 20°


0° viewing angle: iota_20_10000_4_4_00_h
30° viewing angle: iota_20_10000_4_4_30_h
60° viewing angle: iota_20_10000_4_4_60_h
90° viewing angle: iota_20_10000_4_4_90_h

Orbital plane 40°


0° viewing angle: iota_40_10000_4_4_00_h
30° viewing angle: iota_40_10000_4_4_30_h
60° viewing angle: iota_40_10000_4_4_60_h
90° viewing angle: iota_40_10000_4_4_90_h

Orbital plane 50°


0° viewing angle: iota_50_10000_4_4_00_h
30° viewing angle: iota_50_10000_4_4_30_h
60° viewing angle: iota_50_10000_4_4_60_h
90° viewing angle: iota_50_10000_4_4_90_h

Orbital plane 60°


0° viewing angle: iota_60_10000_4_4_00_h
30° viewing angle: iota_60_10000_4_4_30_h
60° viewing angle: iota_60_10000_4_4_60_h
90° viewing angle: iota_60_10000_4_4_90_h



These sounds were all made by former UROP alumna Pei-Lan Hsu using code written by Hughes.