Abstract: By placing rings in the duct to gradually increase the effective admittance of the cylindrical duct along the axis, the sonic black hole (SBH) effect in the duct is realized. The propagation speed will tend to zero as waves propagate toward the end of the SBH, and the sound waves will not reflect, because it will then never reach the end of the duct. Thus, the SBH has the broadband sound absorption performance. Firstly, the sound absorption performance of SBH is analyzed theoretically. Then SBH structures with different sizes are designed, and the influence of physical parameters of the SBH on the sound absorption performance is investigated by experiments. The experimental results reveal that the SBH structure can achieve broadband sound absorption when the number of rings exceeds 20. Furthermore, it is found that the effective sound absorption frequency band moves to lower frequency when the duct length increases and the number of rings are the same. For ducts of the same length, the sound absorption performance will be improved when the number of rings increases.