  In this paper, we consider the Cauchy problem of a model in nonlinear
acoustic, named the Jordan--Moore--Gibson--Thompson equation. This equation
arises as an alternative model to the well-known Kuznetsov equation in
acoustics. We prove global existence and optimal time decay of solutions in
Besov spaces with a minimal regularity assumption on the initial data, lowering
the regularity assumption required in \cite{Racke_Said_2019} for the proof of
the global existence. Using a time-weighted energy method with the help of
appropriate Lyapunov-type estimates, we also extend the decay rate in
\cite{Racke_Said_2019} and show an optimal decay rate of the solution for
initial data in the Besov space $\dot{{B}}_{2,\infty}^{-3/2}(\mathbb{R}^3)$,
which is larger than the Lebesgue space $L^1(\R^3)$ due to the embedding
$L^1(\mathbb{R}% ^3)\hookrightarrow \dot{{B}}_{2,\infty}^{-3/2}(\mathbb{R}^3)$.
Hence we removed the $L^1$-assumption on the initial data required in
\cite{Racke_Said_2019} in order to prove the decay estimates of the solution.
