Pressure field characteristics of underwater detonation gas jet below and above free water surface

•The three pulsations of the gas bubble of the underwater detonation tube are captured by high speed photography.•The frequency spectrum and energy distribution of the signals in water and in the air are obtained by wavelet transform and fast Fourier transform.•The transmission characteristics of the pulsating signal and the shock wave degenerated by the detonation wave on the water–air interface have been preliminarily analyzed, which proves that the low-frequency pulsating signal has a stronger transmission ability.