Measurements of the backscatter of sound waves from three types of rough surfaces and a 6‐in. stepdown were performed. Linearly frequency‐modulated pulses were used in an effort to reduce fluctuations in the returned pulses caused by turbulence in the air. The use of FM pulses displayed the extreme frequency sensitivity of the backscatter from a very rough surface; however, the FM pulses allowed the returned signal to be averaged over a frequency interval determined by the degree of frequency modulation. Using this type of averaging, it was found that the mean‐square backscatter from all surface types was only weakly dependent upon frequency; similarly, a relatively weak dependence on angle of incidence was found in the range of 0°–60°. The frequency range of the measurements was from 40 to 200 kHz; in this range the transmitted signal was linearly frequency modulated by 10, 20, and 40 kHz from initial frequencies of 40, 80, 120, and 160 kHz.