Based on the theory of electric transmission line and the electroacoustic analogy method, the T_type equivalent network of the acoustic waveguide which is uniform and finitely long is derived in which plane wave propagate and the formula of its impedance transfer is obtained as well by means of the equivalent circuit analysis.

Methods Transtelephonic monitoring(TTM) was performed for 24～48 hours in 200 aged silent myocardial ischemia(SMI) patients who was asymptomaticin in one week,at the same time,dynamic electrocardiographic(DCG) monitoring was performed for24-hour in the same patients to observe SMI and arrhythmia incidence.