The propagation of time harmonic acoustic Bloch waves in periodic waveguides is investigated experimentally and the findings compared with those of a theoretical investigation. The waveguides under study are air‐filled rectangular aluminum ducts that are loaded with a periodic array of rigidly terminated rectangular side branches. The two parameters that characterize the Bloch waves, the Bloch wave number and the relative component wave amplitude, are measured and found to compare well with the theory. The band structure that is a well‐known characteristic of Bloch wave dispersion is clearly evident in both parameters, and the features of the band structure are as predicted. The similarities and differences that, according to the theory, are allowed to exist between the forward and the backward traveling Bloch waves are likewise reflected in the measurements.