科研之友
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摘要
To obtain a continuous sound source of underwater explosion, metal grid of detonating cords was designed. The pressure tests and the bubble pulsation experiments were conducted to investigate sound pressure level properties, sound duration and reverberation effect of underwater explosion about metal grid of detonating cords. The spectrum characteristics of underwater explosion signal were analyzed with Hilbert-Huang transform. The results showed that underwater explosion about metal grid of detonating cords could produce more than one pulse wave signal continuously, and form stable continuous wave. Subsequently, the produced bubble pulsation and reverberation effect could significantly improve the duration of underwater explosion. Detonating grid structure, had a strong sound power, and the highest sound pressure level of underwater explosion could reach 249 dB. Even after blasting 60 ms, the sound pressure level of the detonating cords was still above the 200 dB. Frequency range of the underwater explosion sound about metal grid of detonating cords was wide and became the highest when the energy of the low frequency band was below 100 kHz. The frequency components of the pulse signal were rich, and had the characteristics of low frequency and instant, and most of them were below 100 kHz, especially 50 kHz. The pulse shock signal had multiple energy peaks, and the energy value was more concentrated. The fluctuation energy was basically concentrated on the frequency range of 100 kHz, especially, the energy of the low frequency of below 50 kHz was the largest. Moreover, for the frequency above 100 kHz, their energy components were very small. The number and duration of the pulse shock wave could be controlled by the arrangement and the length of metal grid of detonating cords. The time interval between the pulse shock wave was adjustable, and the device was stable and easy to control.
