Chirp sonar reflection profiles of gassy and gas‐free seabeds are quantitatively compared to show the effects of sediment gas on normal incidence backscattering measurements. Acoustic FM pulses that sweep over the band of 2 to 10 kHz are generated by the chirp sonar and compressed using a correlation filter to generate a bandlimited impulse response of the seabed. The amplitude spectrum of the ideal wavelet (the unattenuated, compressed FM pulse) and the spectrum of wavelets backscattered from gassy sediments are used to investigate the frequency dependence of backscattering from gassy seabeds. [Work supported by ONR.]