Abstract: A general method for simultaneously measuring longitudinal and shear wave speeds in materials under load via echo or transmission is described. This process proceeds in simple steps. Users load a specimen, either compressionally, tensilely, or torsionally and the loading is directed along a loading axis. Users connect a transducer with the specimen without loading the transducer and connect the transducer with a data collection apparatus. An ultrasonic pulse is launched from the transducer into the specimen along the loading axis, simultaneously triggering the data collection apparatus. The user measures signals on the data collection apparatus, allowing the user to calculate longitudinal wave speeds and shear wave speeds, whereby both longitudinal wave speeds and shear wave speeds of specimens under load can be measured simultaneously using one transducer. A novel device for measuring longitudinal and shear wave speeds in materials simultaneously is also described.