  Acoustic analogue computation and signal processing are of great
significance, however, it's challenging to realize the acoustic computing
devices because of their limitations of single function and complex structure.
In this paper, an acoustic multifunctional device, which can gate or amplify
acoustic waves without resorting to altering the frequency and structure using
a passive acoustic parity-time (PT)-symmetric metamaterial, is realized
theoretically and experimentally. The metamaterial is constructed by five
lossless-loss periodically distributed media which are modulated to achieve the
passive PT symmetry. At the coherent perfect absorber (CPA)-emitter point in
the broken PT-symmetric phase, the logic gates (AND, OR, XOR and NOT) and small
signal amplifier are realized in a single system by adjusting the phase and
amplitude differences between two incoming beams, respectively. This work
provides a new route for the connection between the PT symmetry and the
acoustic metamaterial, which has great potential applications in acoustic
modulation and acoustic multifunctional device.
