  Since the quality factor of an acoustic wave resonator (AWR) reached
$10^{11}$, AWRs have been regarded as a good carrier of quantum information. In
this paper, we propose a scheme to construct a NOON state with two AWRs
assisted by a nitrogen-vacancy-center ensemble (NVE). The two AWRs cross each
other vertically, and the NVE is located at the center of the crossing. By
considering the decoherence of the system and using resonant interactions
between the AWRs and the NVE, and the single-qubit operation of the NVE, a NOON
state can be achieved with a fidelity higher than $98.8\%$ when the number of
phonons in the AWR is $N \le 3$.
