Sensor arrays are commonly used for condition monitoring in mechanical equipment. However, traditional wireless communication faces challenges in closed metal enclosures due to electromagnetic shielding, making effective transmission difficult. Ultrasonic waves, capable of penetrating metal structures, show significant potential as carriers for information transmission. While multi-channel synchronous transmission can enhance communication efficiency, signal crosstalk remains a pressing issue. To address this, this paper proposes a crosstalk suppression technique based on acoustic metamaterials. By utilizing the bandgap effect of Lamb wave dispersion curves, the method blocks the propagation of sound waves between channels. The metamaterial structure is designed through numerical simulation to determine the bandgap range, and experiments are conducted to verify the effectiveness of crosstalk suppression. The study successfully achieves independent communication across three channels, significantly reduces inter-channel crosstalk, and ensures high decoding accuracy, there by meeting the communication requirements in closed metal structures. This research provides a novel and effective solution to the crosstalk issue in multi-channel ultrasonic communication.