Ship radiation noise evaluation method under low signal-to-noise ratio based on single hydrophone

Abstract

According to the ship radiation noise evaluation method under the low signal-to-noise ratio based on the single hydrophone, calculation methods such as data averaging and distance correction are improved, the data processing flow is optimized, and accurate evaluation of ship radiation noise under the low signal-to-noise ratio is achieved. The method specifically comprises the following data processing methods and processes: (1) data recording: determining recording starting and ending positions according to the length, the navigational speed and the positive transverse distance of a ship; (2) data framing: non-overlapping framing is carried out, and the frame length is determined according to the data length and the navigational speed; (3) data averaging: carrying out index peak value averaging on each frame of data; (4) distance correction: calculating an equivalent distance according to the ship length and the positive transverse distance, and performing sound source level reduction by adopting the equivalent distance; (5) a data processing flow: 1, intercepting a sample; (2) sample framing; (3) averaging each frame; (4) calculating an equivalent distance; and (5) carrying out equivalent distance correction on the averaged data to obtain a radiation noise evaluation result.

Description

Technical Field

[0001] The present invention belongs to the field of experiment and test technology, and provides a method for evaluating ship radiated noise under low signal-to-noise ratio based on a single hydrophone, which is used for accurately evaluating ship radiated noise when the signal-to-noise ratio condition does not meet the requirements of relevant ship radiated noise measurement standards. Background Art

[0003] ANSI S12.64 "Ship Underwater Radiated Noise Measurement Standard" uses multiple non-directional scalar hydrophones to measure ship navigation radiated noise, and the sea area selected is mostly near the port. However, with the continuous improvement of ship acoustic design and construction technology, as well as the increase in human factors such as shipping in nearshore areas and offshore construction, the marine environmental noise has gradually increased, and it has become increasingly difficult to accurately measure ship radiated noise. In the current relevant ship radiated noise measurement standards, the measurement signal-to-noise ratio condition must be greater than or equal to 3dB, and the data processing process mainly includes effective sample interception, data power spectrum analysis, environmental noise impact correction, sound propagation loss reduction, and multiple noise sample averaging. The above measurement standards and data analysis processes can accurately evaluate the ship noise characteristics when the measurement signal-to-noise ratio meets the requirements. However, when the marine environmental noise is high and the measurement signal-to-noise ratio is insufficient, it will be difficult to obtain accurate calculation results. How to accurately measure and evaluate ship radiated noise in complex marine environmental noise has always been a key issue in ship acoustic stealth design and equipment vibration reduction and noise reduction. Summary of the invention

[0004] In order to solve the problems existing in the existing ship radiated noise measurement methods, the present invention provides a ship radiated noise evaluation method under low signal-to-noise ratio based on a single hydrophone. The radiated noise recording conditions, noise data averaging methods, propagation loss correction methods, etc. that affect the accuracy of ship navigation radiated noise data analysis are studied, the noise data processing process is optimized, and finally the accurate evaluation of ship radiated noise under insufficient signal-to-noise ratio conditions is achieved.

[0005] The ship radiated noise assessment process proposed in this invention is as follows: Figure 2 As shown, it includes the following measurement conditions and data processing flow:

[0006] (1) Radiated noise recording conditions: Determine the starting and ending positions and recording duration of radiated noise recording according to the length, speed and forward and horizontal distance of the ship under test;

[0007] (2) Noise data framing method: Noise data is framed without overlap. The duration of each frame is determined based on the noise recording duration and the ship speed in condition (1).

[0008] (3) Noise data averaging method: The data after frame division in condition (2) is averaged using the exponential peak averaging method;

[0009] (4) Propagation loss correction method: Based on the length and transverse distance of the measured ship, the equivalent distance covering all noise data is calculated, and the sound source level distance is calculated using the equivalent distance;

[0010] (5) Noise data processing flow: According to the starting position and the ending position in condition (1), the noise data samples are intercepted; according to the duration of each frame in condition (2), the noise data samples are divided into frames without overlap; according to the averaging method in condition (3), the data after framing are subjected to exponential peak averaging; according to the equivalent distance in condition (4), the noise data after averaging is corrected for propagation loss, and the ship radiated noise assessment results under low signal-to-noise ratio are obtained.

[0011] The beneficial effects of the present invention are:

[0012] Under high signal-to-noise ratio conditions, the measurement accuracy of ship radiated noise is guaranteed, and under low signal-to-noise ratio conditions, background noise interference is effectively suppressed to obtain accurate evaluation results of ship radiated noise. Figure 4 shown. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of single hydrophone measurement method for ship radiated noise

[0014] Figure 2 Schematic diagram of the ship radiated noise assessment process under low signal-to-noise ratio

[0015] Figure 3 Error analysis diagram of distance correction using fitting distance

[0016] Figure 4 Comparison diagram of the data estimation method of the present invention and the spectrum analysis of the actual radiation noise DETAILED DESCRIPTION

[0017] The specific implementation method of the present invention is described in detail below in combination with the simulation data of ship navigation radiation noise and the accompanying drawings. The following implementation cases will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be pointed out that for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0018] The ship radiated noise evaluation method under low signal-to-noise ratio based on a single hydrophone of the present invention is measured as follows Figure 1 As shown in the figure, a measuring hydrophone is deployed at a transverse distance d from the measured ship's route. The measured ship sails through the measurement area in a straight line at a uniform speed, and the effective measurement range is greater than or equal to twice the ship's length L. The real-time distance between the measured ship and the measuring hydrophone is obtained by radio or hydroacoustic ranging methods, and the spatial geometric relationship between the two is constructed.

[0019] According to the measured ship length L, speed v and other information, the time length T of the intercepted noise sample data segment is calculated.

[0020]

[0021] Taking the measured ship and the measuring hydrophone as the center at the time t0, forward T / 2 is the start time of the sample data, and backward T / 2 is the end time of the sample data, the sample data is intercepted to obtain the noise sample data P.

[0022] According to the total duration of the data sample and the speed, the frame duration is calculated, and the noise sample data P is processed into equal intervals without overlap, and P = [p1, p2, ..., p n ]; then perform exponential peak averaging on each data segment according to the following formula to obtain the sound pressure level data PL before the calculated distance.

[0023]

[0024] Calculate the corresponding distance of the noise sample data after framing, r = [r1, r2, ..., r n ], according to the assumption of spherical wave expansion of the ship radiation noise field and the linear average method, the equivalent distance of the measured ship in the range of -L to L can be obtained:

[0025]

[0026] In the formula, R represents the equivalent distance of each data point;

[0027] Using the above-mentioned equivalent distance R and the peak exponential average calculation result PL, the estimated result of the ship radiated noise is calculated by the following formula.

[0028]

[0029] Figure 3 A set of calculation errors estimated using the data of the present invention is given, and its horizontal coordinate is the ratio of the positive and negative distance d to the data average time length T. It can be seen that the above estimation algorithm has high applicability and accuracy. When the ratio of the positive and negative distance d to the average window T is greater than or equal to 1, the error introduced by the estimation algorithm can be controlled within 1dB. However, when the data recording time is long or the speed is high, especially when the positive and negative distance d is much smaller than the ship length L, the estimation algorithm will no longer be applicable.

[0030] The above method was verified using the actual ship noise and environmental noise data obtained from the sea trial. The ship noise characteristics were obtained under static conditions without background noise interference. Gaussian white noise was superimposed on the pure ship noise to obtain the ship noise data containing interference noise. The propagation loss was corrected according to the spherical expansion. When the frequency is higher than 1kHz, the ship noise cannot be distinguished because it is buried in the environmental noise. This shows that when the measured data range exceeds the ship length -L~L, it will be affected by environmental noise at the beginning and end of the data.

[0031] Figure 4 The estimation results of ship radiated noise under low signal-to-noise ratio using the present invention are given. It can be seen that when there is background noise interference, better calculation results can be obtained by first performing exponential averaging of noise data peak values ​​and corrected distance fitting averaging, and then performing sound source level reduction according to spherical expansion. At the same time, when there is no background noise interference, the correct results are still maintained. The exponential peak averaging algorithm gives the best results. Compared with the real noise spectrum, the maximum calculation error of this method is only 1.3dB.

[0032] In summary, the above are only preferred implementation examples of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for evaluating ship radiated noise under low signal-to-noise ratio based on a single hydrophone, characterized in that: Accurate evaluation of ship radiated noise under low measurement signal-to-noise ratio is achieved using a single non-directional scalar hydrophone.

2. The method for evaluating ship radiated noise under low signal-to-noise ratio based on a single hydrophone according to claim 1, characterized in that: The following noise measurement conditions are included: (1) Radiated noise recording conditions: Determine the starting and ending positions and recording duration of radiated noise recording according to the length, speed and forward and horizontal distance of the ship under test; (2) Noise data framing method: Noise data is framed without overlap. The duration of each frame is determined based on the noise recording duration and the ship speed in condition (1). (3) Noise data averaging method: The data after frame division in condition (2) is averaged using the exponential peak averaging method; (4) Propagation loss correction method: Based on the length and transverse distance of the measured ship, the equivalent distance covering all noise data is calculated, and the sound source level distance is calculated using the equivalent distance; (5) Noise data processing flow: According to the start position and end position in condition (1), intercept the noise data samples; according to the duration of each frame in condition (2), divide the noise data samples into frames without overlap; according to the averaging method in condition (3), perform exponential peak averaging on the framed data; According to the equivalent distance in condition (4), the propagation loss correction is performed on the noise data after average processing to obtain the evaluation result of ship radiated noise under low signal-to-noise ratio.

Images