Though the velocity of ultrasonic waves passing through materials is a highly preferred parameter to indirectly and non-destructively determine the strength properties of rock and concrete, many studies have emphasized that such waves are influenced by many factors, such as sample diameter, length, and measurement techniques (semi-direct or indirect). Direct techniques use opposite sides of the materials, semidirect techniques use adjacent faces, and indirect techniques use the same face. In contrast to the results given in many studies so far, the results from this study indicate that the ultrasonic wave velocity is not dependent on the sample geometry and measurement techniques. The tests conducted on the materials of three different lengths showed that ultrasonic wave velocity was not affected by sample length because the differences in values obtained from different lengths were < 0.5% for both the polypropylene and rock samples and 1.5% for the concrete samples. The ultrasonic tests were performed on the samples for four different diameters and the differences in values were < 1.2% for the polypropylene samples and 1.8% for concrete the samples. The results of testing the different techniques showed that when the travel distance increases, the differences between the values obtained by different methods decrease and this difference is < 3% if the sample length is > 20 cm. The results clearly indicated that the ultrasonic velocity value of the materials is related to the material homogeneity rather than the sample diameter, length, and different measurement techniques.