中国物理B ›› 2024, Vol. 33 ›› Issue (3): 34301-034301.doi: 10.1088/1674-1056/ad108f

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High-order Bragg forward scattering and frequency shift of low-frequency underwater acoustic field by moving rough sea surface

Ya-Xiao Mo(莫亚枭)1,†, Chao-Jin Zhang(张朝金)2, Li-Cheng Lu(鹿力成)1, Qi-Hang Sun(孙启航)3, and Li Ma(马力)1   

  1. 1 Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, Chinese Academy of Sciences (CAS), Beijing 100190, China;
    2 China State Shipbuilding Corporation Systems Engineering Research Institute, Beijing 100094, China;
    3 Little Bird Co., Ltd, Beijing 100089, China
  • 收稿日期:2023-05-26 修回日期:2023-11-23 接受日期:2023-11-29 出版日期:2024-02-22 发布日期:2024-02-29
  • 通讯作者: Ya-Xiao Mo E-mail:moyaxiao@mail.ioa.ac.cn
  • 基金资助:
    Project supported by the IACAS Young Elite Researcher Project (Grant No. QNYC201703), the Rising Star Foundation of Integrated Research Center for Islands and Reefs Sciences, CAS (Grant No. ZDRW-XH-2021-2-04), and the Key Laboratory Foundation of Acoustic Science and Technology (Grant No. 2021-JCJQ-LB-066-08).

High-order Bragg forward scattering and frequency shift of low-frequency underwater acoustic field by moving rough sea surface

Ya-Xiao Mo(莫亚枭)1,†, Chao-Jin Zhang(张朝金)2, Li-Cheng Lu(鹿力成)1, Qi-Hang Sun(孙启航)3, and Li Ma(马力)1   

  1. 1 Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, Chinese Academy of Sciences (CAS), Beijing 100190, China;
    2 China State Shipbuilding Corporation Systems Engineering Research Institute, Beijing 100094, China;
    3 Little Bird Co., Ltd, Beijing 100089, China
  • Received:2023-05-26 Revised:2023-11-23 Accepted:2023-11-29 Online:2024-02-22 Published:2024-02-29
  • Contact: Ya-Xiao Mo E-mail:moyaxiao@mail.ioa.ac.cn
  • Supported by:
    Project supported by the IACAS Young Elite Researcher Project (Grant No. QNYC201703), the Rising Star Foundation of Integrated Research Center for Islands and Reefs Sciences, CAS (Grant No. ZDRW-XH-2021-2-04), and the Key Laboratory Foundation of Acoustic Science and Technology (Grant No. 2021-JCJQ-LB-066-08).

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摘要： Acoustic scattering modulation caused by an undulating sea surface on the space-time dimension seriously affects underwater detection and target recognition. Herein, underwater acoustic scattering modulation from a moving rough sea surface is studied based on integral equation and parabolic equation. And with the principles of grating and constructive interference, the mechanism of this acoustic scattering modulation is explained. The periodicity of the interference of moving rough sea surface will lead to the interference of the scattering field at a series of discrete angles, which will form comb-like and frequency-shift characteristics on the intensity and the frequency spectrum of the acoustic scattering field, respectively, which is a high-order Bragg scattering phenomenon. Unlike the conventional Doppler effect, the frequency shifts of the Bragg scattering phenomenon are multiples of the undulating sea surface frequency and are independent of the incident sound wave frequency. Therefore, even if a low-frequency underwater acoustic field is incident, it will produce obvious frequency shifts. Moreover, under the action of ideal sinusoidal waves, swells, fully grown wind waves, unsteady wind waves, or mixed waves, different moving rough sea surfaces create different acoustic scattering processes and possess different frequency shift characteristics. For the swell wave, which tends to be a single harmonic wave, the moving rough sea surface produces more obvious high-order scattering and frequency shifts. The same phenomena are observed on the sea surface under fully grown wind waves, however, the frequency shift slightly offsets the multiple peak frequencies of the wind wave spectrum. Comparing with the swell and fully-grown wind waves, the acoustic scattering and frequency shift are not obvious for the sea surface under unsteady wind waves.

关键词: high-order Bragg scattering, frequency shift, low-frequency acoustic field, moving rough sea surface

Abstract: Acoustic scattering modulation caused by an undulating sea surface on the space-time dimension seriously affects underwater detection and target recognition. Herein, underwater acoustic scattering modulation from a moving rough sea surface is studied based on integral equation and parabolic equation. And with the principles of grating and constructive interference, the mechanism of this acoustic scattering modulation is explained. The periodicity of the interference of moving rough sea surface will lead to the interference of the scattering field at a series of discrete angles, which will form comb-like and frequency-shift characteristics on the intensity and the frequency spectrum of the acoustic scattering field, respectively, which is a high-order Bragg scattering phenomenon. Unlike the conventional Doppler effect, the frequency shifts of the Bragg scattering phenomenon are multiples of the undulating sea surface frequency and are independent of the incident sound wave frequency. Therefore, even if a low-frequency underwater acoustic field is incident, it will produce obvious frequency shifts. Moreover, under the action of ideal sinusoidal waves, swells, fully grown wind waves, unsteady wind waves, or mixed waves, different moving rough sea surfaces create different acoustic scattering processes and possess different frequency shift characteristics. For the swell wave, which tends to be a single harmonic wave, the moving rough sea surface produces more obvious high-order scattering and frequency shifts. The same phenomena are observed on the sea surface under fully grown wind waves, however, the frequency shift slightly offsets the multiple peak frequencies of the wind wave spectrum. Comparing with the swell and fully-grown wind waves, the acoustic scattering and frequency shift are not obvious for the sea surface under unsteady wind waves.

Key words: high-order Bragg scattering, frequency shift, low-frequency acoustic field, moving rough sea surface

中图分类号:  (Scattering of acoustic waves)

  • 43.20.Fn
43.30.Hw (Rough interface scattering) 43.30.Re (Signal coherence or fluctuation due to sound propagation/scattering in the ocean) 43.30.Es (Velocity, attenuation, refraction, and diffraction in water, Doppler effect)