Theoretical expressions for the spectral density of amplitude, amplitude‐difference, and phase‐difference fluctuations of waves propagating over a line‐of‐sight path in a weakly scattering turbulent medium are derived. Experimental observations made at radio (35 GHz) and acoustic (3 kHz) frequencies are in good agreement with the theoretical predictions under a variety of meteorological conditions. Comparison of experimental and theoretical spectra yields a measure of the average across‐the‐path wind velocity and the average refractive‐index structure constant Cn. In general, wind speeds and refractive‐index structure constants inferred from simultaneous meteorological measurements agree with those obtained from propagation data.