Subrings of the asymptotic Hecke algebra of type $H_4$

The structure of subring $J^{\Gamma \cap \Gamma^{-1}}$ of the asymptotic Hecke algebra is described for $\Gamma$ a left cell of the Coxeter group of type $H_4$. A small set of generators is produced. The subalgebras spanned by a subset of the basis ${t_x}_{x\in \Gamma\cap\Gamma^{-1}}$ are determined.