Sonic velocity of knitted fabric samples was measured by Dynamic Modulus Tester, and the relationship between changes in the mechanical properties and their sonic velocity was investigated. Through the measurements, sonic velocity was found to be highly correlated not only with fabric static elastic modulus but also with fabric breaking strength, breaking extension, and work of rupture. Sonic velocity, as found, depends on the direction of measurement, walewise or coursewise, and is a linear function of the number of wales and courses per centimeter and loop-shaped factor. Furthermore, the effect of applying dynamical loading on the fabric leads to changes in fabric mechanical and structural properties, which can be patterned through the measurement of their sonic velocity. The dynamic modulus tester measured the velocity of sonic pulses in materials. This technique will help in prediction of the change in mechanical properties of the fabric tensioned structures during their service life.