In addition to instrumentation accuracy and test repeatability, the correlation of asphalt test data is very dependent on targeted “known” properties of asphalt samples or cores, such as air voids. In the case of air voids, sample preparation targets the desired sample attribute, however an assessment of the true air voids and their distribution within asphalt samples remains a challenge. Current assessment is usually via visual inspection and measuring the total air voids within the sample. However, such an approach fails to evaluate important factors such as air voids distribution and aggregate structure. In the case of testing regimes that are localised on test samples, the true air voids at the test location is essential for proper data correlation. In this study, an Ultrasonic Wave Transmission (UWT) technique was developed and applied as a non-destructive test to better assess the true localised air void properties of asphalt samples. The data correlation outcomes significantly changed the performance rankings of asphalt mixes and indicated that the UWT technique has excellent potential as a supplementary tool for evaluating asphalt laboratory samples.