# Underwater Noise Characteristics of the Tidal Inlet of Zhanjiang Bay

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Research Area

^{9}m

^{3}, with a maximum tidal volume of up to 10 × 10

^{9}m

^{3}. The tidal current velocity ranges from 0.5 to 1.5 m/s, making it an area with a relatively large tidal range along the coast of South China [22,23,24,25]. During high tides, the tidal current flows from the deep channel outside the bay into the bay; during low tides, the tidal current flows from the bay to the outside of the bay. The tidal current during a high tide mainly flows westward, while during low tides, it mainly flows eastward. In the offshore area outside the bay mouth, wind waves are the main hydrodynamic factor, with prevailing winds and waves from the eastern and northern directions.

## 3. Materials and Methods

#### 3.1. Data Collection

#### 3.2. Data Processing

_{s}is the sampling frequency of the hydrophone. In Equation (2), F is the Fourier transform of the discrete signal. The window function is the Hann window, with a window shift of 50%. The duration for each frame of data is 1 s. In Equation (3), M represents the sensitivity of the hydrophone.

## 4. Results

#### 4.1. Analysis of Noise Spectrum in a Bay Environment

#### 4.2. Tidal Level and Sound Pressure Level Characteristics

## 5. Discussion

## 6. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

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**Figure 1.**This layout and station diagram of hydrophones: (

**a**) station diagram (“a” “b” and “c” serve as data collection points); (

**b**) layout method.

**Figure 4.**Underwater noise spectrograms in autumn: (

**a**) 5 m, station a; (

**b**) 5 m, station b; (

**c**) 5 m, station c; (

**d**) 10 m, station a; (

**e**) 10 m, station b; (

**f**) 10 m, station c.

**Figure 5.**Underwater noise spectrograms in spring: (

**a**) 5 m, station a; (

**b**) 5 m, station b; (

**c**) 5 m, station c; (

**d**) 10 m, station a; (

**e**) 10 m, station b; (

**f**) 10 m, station c; (

**g**) 20 m, station a; (

**h**) 20 m, station b; (

**i**) 20 m, station c.

**Figure 9.**Underwater noise sound pressure level and tidal variation curves: (

**a**) autumn at 5 m; (

**b**) autumn at 10 m; (

**c**) spring at 5 m; (

**d**) spring at 10 m; (

**e**) spring at 20 m.

**Figure 10.**Underwater noise frequency correlation matrix in autumn: (

**a**) 5 m, station a; (

**b**) 5 m, station b; (

**c**) 5 m, station c; (

**d**) 10 m, station a; (

**e**) 10 m, station b; (

**f**) 10 m, station c.

**Figure 11.**Underwater noise frequency correlation matrix in spring: (

**a**) 5 m, station a; (

**b**) 5 m, station b; (

**c**) 5 m, station c; (

**d**) 10 m, station a; (

**e**) 10 m, station b; (

**f**) 10 m, station c; (

**g**) 20 m, station a; (

**h**) 20 m, station b; (

**i**) 20 m, station c.

**Figure 12.**Oceanic environmental noise spectrum distribution chart (modified from reference [2], the green curve represents the results of this study).

Station | Date | Latitude | 1st | 2nd | 3rd | 4th |
---|---|---|---|---|---|---|

a | 9 December 2022 | 110°32′23″; 21°04′43″ | 08:02–08:07 | 12:13–12:18 | 12:44–12:49 | 15:43–15:48 |

b | 9 December 2022 | 110°32′24″; 21°05′12″ | 09:21–09:26 | 11:00–11:05 | 13:17–13:22 | 14:48–14:53 |

c | 9 December 2022 | 110°32′38″; 21°05′31″ | 09:33–09:38 | 10:34–10:39 | 13:42–13:47 | 14:05–14:08 |

a | 21 March 2023 | 110°32′23″; 21°04′43″ | 09:00–09:05 | 12:39–12:44 | 13:06–13:11 | 16:51–16:56 |

b | 21 March 2023 | 110°32′24″; 21°05′12″ | 09:37–09:42 | 11:57–12:02 | 14:29–14:34 | 16:15–16:20 |

c | 21 March 2023 | 110°32′38″; 21°05′31″ | 10:27–10:32 | 11:10–11:15 | 14:40–14:45 | 15:52–15:57 |

Number | Station | Probability Interval 5 m (dB) | Probability Interval 10 m (dB) | Probability Interval 20 m (dB) | Probability Peak 5 m (dB) | Probability Peak 10 m (dB) | Probability Peak 20 m (dB) |
---|---|---|---|---|---|---|---|

Autumn | a | (53–78) | (63–79) | / | 69.1 | 68.7 | / |

b | (52–77) | (61–70) | / | 63.6 | 68.5 | / | |

c | (57–77) | (60–69) | / | 67.3 | 68.8 | / | |

Spring | a | (62–78) | (62–78) | (60–77) | 70.0 | 75.7 | 71.4 |

b | (61–79) | (62–81) | (62–78) | 73.5 | 79.8 | 70.9 | |

c | (62–78) | (63–81) | (62–70) | 75.2 | 82.4 | 74.5 |

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**MDPI and ACS Style**

Huo, X.; Zhang, P.; Yuan, Y.; Li, G.; Tang, J.; Shi, B.
Underwater Noise Characteristics of the Tidal Inlet of Zhanjiang Bay. *Water* **2023**, *15*, 3586.
https://doi.org/10.3390/w15203586

**AMA Style**

Huo X, Zhang P, Yuan Y, Li G, Tang J, Shi B.
Underwater Noise Characteristics of the Tidal Inlet of Zhanjiang Bay. *Water*. 2023; 15(20):3586.
https://doi.org/10.3390/w15203586

**Chicago/Turabian Style**

Huo, Xinze, Peizhen Zhang, Yiquan Yuan, Gaocong Li, Jieping Tang, and Benwei Shi.
2023. "Underwater Noise Characteristics of the Tidal Inlet of Zhanjiang Bay" *Water* 15, no. 20: 3586.
https://doi.org/10.3390/w15203586