  Acoustic holograms are the keystone of modern acoustics. It encodes
three-dimensional acoustic fields in two dimensions, and its quality determine
the performance of acoustic systems. Optimisation methods that control only the
phase of an acoustic wave are considered inferior to methods that control both
the amplitude and phase of the wave. In this paper, we present Diff-PAT, an
acoustic hologram optimisation algorithm with automatic differentiation. We
demonstrate that our method achieves superior accuracy than conventional
methods. The performance of Diff-PAT was evaluated by randomly generating 1000
sets of up to 32 control points for single-sided arrays and single-axis arrays.
The improved acoustic hologram can be used in wide range of applications of
PATs without introducing any changes to existing systems that control the PATs.
In addition, we applied Diff-PAT to acoustic metamaterial and achieved an >8 dB
increase in the peak noise-to-signal ratio of acoustic hologram.
