Fig. 5: Physiological monitoring applications of the acoustic textile system.

a, Illustration of muscle state monitoring using a SISO system. A fibre woven into a close-fitting garment can detect muscle relaxation and tension states. b, Time–frequency spectrograms of \({R}_{x}\) received signals under muscle relaxation and tension states. The clear distinction of states can effectively indicate muscle status in real time. c, Results from monitoring of the arm muscles in periodic motion. The periodic variation in \({R}_{x}\) peak-to-peak amplitude effectively monitors muscle state. d, Illustration of abdominal breathing in the human body. An acoustic textile can use the rhythmic rise and fall of the belly to achieve respiratory monitoring. e, Image showing integration of a SISO system into the abdominal area of a cloth shirt. f, Spectrograms of \({R}_{x}\) received signals under exhalation and inhalation states. g, Abdomen movement sensing data measured during periodic breathing. The variation in \({R}_{x}\) peak-to-peak amplitude identifies the rise and fall of the abdomen, corresponding to exhalation and inhalation states. h, Continuous monitoring and diagnosis of simulated abnormal respiratory rate (in BPM). The periodic variation in \({R}_{x}\) peak-to-peak amplitude effectively monitors respiratory rate and could provide timely alerts for abnormal conditions such as tachypnea. Scale bars, 100 mm.