The specification for oceanographic survey swivey of acoustical and optical parameters in the sea
Some standard content:
National Standard of the People's Republic of China
Oceanographic Survey Specification
Ocean Acoustic and Optical Parameters Survey
The specification for oceanographic surveyswivey of acoustical and optical parameters in the sea Subject Content and Scope of Application
This standard specifies the technical requirements, observation methods and data compilation for ocean acoustic and optical parameters survey. GB 12763. 5 91
This standard applies to the ocean acoustic and optical parameters survey, and can also be applied to the acoustic and optical parameters measurement of rivers and lakes. Reference Standards
GB12763.1 General Rules for Oceanographic Survey Specification
GB[2763.2 Oceanographic Survey Specification Ocean Hydrological Observation GB12763.3 Oceanographic Survey Specification Ocean Meteorological Observation GB12763.6 Oceanographic Survey Specification Ocean Biological Survey GB 12763. 7
GB3241
GB4128
GB3785
Ocean survey specificationsOcean survey data processing1/1 and 1/3 octave band filters for sound and vibration analysisStandard hydrophones
Electrical and acoustic properties and test methods of sound level metersGB3102.6Quantities and units of light and related electromagnetic radiationPart I General provisions
3 Technical design of survey tasks
The professional person in charge of the survey task must undertake the technical design of the task3.2 The contents of the technical design are as follows:
Survey project,
Submitted materials, results and requirements for results; survey area, layout of survey stations,
Survey methods, methods and quality control requirements: Survey instruments and equipment!
Requirements for survey ships and voyages;
Survey, time arrangement;
Organization and professional configuration of survey personnel.
Approved by the State Administration of Technical Supervision on March 22, 1991 and implemented on January 1, 1992
4 Station layout and standard layers
4.7 Determine the stations according to the purpose of the survey. GB 12763.5:-91
4.2 The survey station locations of acoustic elements shall be determined according to the horizontal changes of the elements, or determined according to the needs of marine acoustic engineering. In comprehensive surveys, the stations for seawater sound velocity surveys shall be consistent with the stations for temperature and salt surveys. 4.3 The survey stations of optical elements can be determined according to the needs of special surveys and the horizontal gradient of optical elements in the measured sea area. For general large-scale surveys, the stations can be 20 nmile apart in the near-shore area and 60 nmile apart in the far-flung area. 4.4 Except for seawater sound velocity, there is generally no standard layer for acoustic element surveys. The standard layer for seawater sound velocity surveys is consistent with the layer for temperature and salt surveys. Implement according to GB12763.2.
4.5 The standard layers for underwater irradiance and light transmittance measurement are surface layer, 4, 6, 8, 10, 12, 14, 16, 18. 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200m. If the depth is greater than 200m, the light transmittance should be increased by 500m. 500m and then another layer every 500m. Special requirements are added. The surface layer and bottom layer should comply with the provisions of GB12763.2. 5: Requirements for experimental equipment of survey ships
5.1 There must be an available sound and light measurement laboratory on board, and there must be a laboratory table that can fix the instruments indoors, and there must be a water tank indoors. 5.2 The ship must be equipped with AC and DC power supplies required by the instruments and equipment. 5.3 The ship should be equipped with a working winch. A crane and wire rope with a load greater than 10kN are required for bottom acoustics projects. 5.4 The noise caused by the survey ship should be as small as possible during acoustic measurements. 5.5 The ship should have a navigation positioning system and a meteorological recording system. 6 Instruments and equipment and their use requirements
6-1 The instruments and equipment must be certified by the national metrology agency as products suitable for marine environmental cases. 6.2 Before going out to sea, the name, model, production number, inspection unit, certificate number and inspection results of the instruments and equipment must be registered in a table, and the inspector must sign.
6.3 Instruments and equipment must be calibrated regularly and used within the validity period. B.4 The instruments used must meet the accuracy, resolution and measurement range requirements of the load to be measured. 6.5 Various observation instruments and survey equipment should be carefully checked and debugged before sailing to ensure the good condition of the instruments and equipment. 6.6 During measurement, various factors that interfere with the accuracy of the instrument must be eliminated to ensure the reliability of the measurement data. The instrument must be calibrated after use. The underwater parts should be rinsed with fresh water in time. 6.7
6.8 The operating procedures must be strictly followed when using Sichuan instruments. 7 Provisions for auxiliary measurement
The accuracy and measurement methods of auxiliary measurement in each chapter of this standard can be found in the relevant standards in Chapter 2. Auxiliary measurement and primary measurement are carried out simultaneously or quasi-synchronously.
8 General requirements for original records and data collation 8.1 The handwriting of original records should be neat and clear, and no smudges should be made. Records should be made in black pencil, and the size of the characters should not exceed 2/3 of the grid. If there are errors in the records, cross out the original records and fill in the correct numbers or symbols above the points. 8.2 If the observation data is found to be unqualified or suspicious at the measurement site, it should be re-measured immediately. 8.3 Observation records, transcriptions, calculations, drawings, and reports should be checked and re-calibrated. The staff should sign the work items they undertake. 8.4 Write a report
a. After completing each voyage, the person in charge of the survey technology shall fill in the voyage report form: GB12763.5-91
b. After completing the survey task, the person in charge of the survey professional shall compile a work report. After completing the survey task, the person in charge of the professional and the project leader shall preside over the writing of the survey report, see GB12763.1. Part II Survey of Seawater Sound Velocity
9 Terms, Symbols, Units
9.1 Seawater Sound Velocity
The speed at which sound waves propagate in seawater.
Symbol: c, unit: m/s.
9.2 Sound Velocity Gradient
The rate of change of sound velocity in seawater with depth.
Symbol: G, unit: 5-1.
Gu=dr/d2
Detection, m. Take the sea surface as the origin of?, downward is positive. Where: 2—
is a positive value and is called a positive sound velocity gradient; 2—
is a negative value and is called a negative sound velocity gradient. 9.3 Sound velocity jump layer
A water layer where the sound velocity changes sharply with depth.
9.4 Sound velocity isothermal layer
A water layer where the sound velocity does not change with depth.
9.5 Underwater sound channel
In the ocean, between two planes roughly parallel to the sea surface, the sound velocity changes with depth and passes through a minimum area. The position of the minimum is called the sound channel axis.
If the lower side of the sound channel axis is a deep sea isothermal layer, this underwater sound channel is also called a deep sea sound channel (SOFAR channel). 10 Technical requirements
10. 1 Quantity to be measured
, seawater sound of each water layer at each station:
The depth of each water layer at each station.
10.2 Measurement Technical Indicators
Measurement Base Range
Seawater Sound Velocity Measurement: The general range is 1430~1550m/s, and the limit range is 1400~1600m/s; Depth measurement, from the sea surface to the seabed, but in the ocean it is allowed to only reach the depth where the sound velocity of the deep sea sound channel is the minimum. .10. 2-2
Accuracy
Seawater Sound Velocity Measurement: The first-level standard is that the absolute error does not exceed ±0.20 m/s, and the second-level standard is that the absolute error does not exceed ±0.75 Depth measurement: The accuracy should comply with the provisions of GB12763.2. 11 Measurement Methods
There are two types of measurement methods: direct measurement method and indirect measurement method. The former is the main method, and the latter is the auxiliary method. 11.1 Direct measurement method
11.1.1 Measurement principle
Sound velocity measurement of seawater: The electroacoustic circuit is used to measure the time taken by the sound wave to pass through two fixed points in the water, and the corresponding sound velocity value is indicated; GB12763.5-91
b. Depth measurement: The hanging sound velocity meter uses a depth sensor to measure the depth of the underwater probe. The disposable sound velocity meter uses a consumable probe with a predetermined sinking speed to measure the time after the maneuvering head falls into the water, and the corresponding depth reached by the probe at each moment is indicated. 11.t.2 Instruments and equipment
Seawater sound velocity meter and its terminal recording equipment. 11.13 Measurement requirements
11.1.3.1 Measurement requirements for hanging sound velocity meters. During continuous vertical measurement, the speed of the winch must be controlled to ensure that at least one sound velocity data can be obtained for every 1m lowered: b. During point-by-point fixed depth measurement, the sound velocity data of each standard water layer must be obtained; c. During the observation process, if a sound velocity layer or underwater sound channel is found, when the probe is raised, a continuous vertical measurement should be made in the jump layer or sound channel;
d. During observation, the survey ship should drop anchor or drift. 11.1.3.2. Measurement requirements for disposable sound velocity meters. Before sailing, it is necessary to check that the battery in the probe must not exceed the validity period; before sailing, the signal transmission system from the probe to the processor on board must be debugged: b.
e. During observation at sea, the instrument should be turned on, and the probe can only be deployed after the processor on board works normally. If enameled wire is used to transmit the signal, the line should be drawn smoothly around the water to prevent the line from being broken by the ship hook: d. During observation, if the vertical distribution curve of the sound velocity recorded by the instrument is found to have a large abnormality, it should be re-measured, e. During observation, the survey ship must sail within the speed allowed by the sound velocity meter. 11.2. Indirect measurement method
According to the empirical formula of seawater sound velocity established based on the relationship between seawater sound velocity and water temperature, salinity, and pressure (wearing depth), the depth of each water layer and the seawater sound velocity value are converted through the measurement data of these hydrological parameters. This method is only applicable to sea areas where there is an empirical formula for seawater sound velocity. The sound velocity formula and data processing of ocean water shall comply with GB12763.7. Water temperature and salinity data must reach the first-level accuracy. 11.3 Observation records
Fill the observation results into the seawater sound velocity observation record form (format see Appendix A1) 12 Data collation
12.1 Collation and report of recorded data
. Compile the observation data in chronological order: b, and write reports in the order of stations. The format shall comply with GB12763.7. 12.2 Drawing of sound velocity vertical distribution map, sound velocity cross-sectional distribution map, sound velocity plane distribution map, and sound velocity circumferential change map
According to GB12763.7.
12.2.1 Drawing of sound velocity jump layer characteristic distribution map. Provisions: In this water layer, the absolute value of the average sound velocity gradient is not less than 0.2s-1 in the sea area with a water depth greater than 200m, or not less than 0.5s-1 in the sea area with a water depth of not more than 200m, and the sound velocity difference between the top and bottom of the layer is not less than 1.0m/s, which is a sonic jump layer. The average sound velocity gradient in the jump layer is the sonic jump layer intensity. b The jump layer distribution map to be characterized includes the jump layer intensity, jump layer thickness and jump layer boundary depth distribution map. The measurement and drawing methods of each characteristic quantity shall comply with GB 12763.7.
12.2.2 Drawing of the channel characteristic distribution map
The channel characteristic distribution map includes the sound velocity on the channel axis, the channel axis depth, and the upper and lower boundary depth distribution maps of the channel. 12.2.2.1 Measurement of each characteristic quantity, on the sound velocity vertical distribution map. The minimum sound velocity is the sound velocity on the sound channel axis; b. The depth where the minimum sound velocity is located is the depth of the sound channel axis; GB12763.591
: The top boundary of the negative gradient layer on the upper side of the sound channel axis and the bottom boundary of the positive gradient layer on the lower side, the one with the smaller sound velocity value is one boundary of the sound channel, and on the outer side, the place where the sound velocity value is equal to the determined boundary is the other boundary of the sound channel. The shallower of the two boundaries is called the upper boundary, and the deeper one is called the lower boundary. The depth is the depth of the upper and lower boundaries of the sound channel. 12.2.2.2 Drawing method: Fill in the characteristic values of the sound channel at each station on the sea area base map, draw contour lines by interpolation, mark the value in the middle of the line, and the interval of the contour lines depends on the specific situation. Use the outer shadow line to draw the range of the sound channel area, and indicate "no sound channel area" outside the range. When double sound appears, the upper and lower sound channels are plotted separately, and the scope of the double sound channel area is drawn with a dotted line, indicating "double sound channel area". 12.2.3 Drawing of the sound velocity vertical distribution type area map 12.2.3.1 stipulates
a. In the water layer, the absolute value of the sound velocity gradient is not greater than 0.01s-1, which can be regarded as a sound velocity uniform layer, b. Codes for several common sound velocity vertical distribution types Type 1: heavy vertical uniform structure;
"Type: upper uniform layer-positive gradient layer-lower uniform layer structure; Type: upper uniform layer-negative gradient layer-positive gradient layer-lower uniform layer structure: Type IV: upper uniform layer-negative gradient layer-lower uniform layer structure; Type V: upper uniform layer-positive gradient layer-negative gradient layer-lower uniform layer structure, the upper uniform layer and lower uniform layer in Type I to Type V are optional, c. Other The codes for other types of vertical distribution of sound velocity are named by themselves with Roman numerals above V or Arabic numerals below Roman numerals. d. Guaranteed mean error rate: refers to the statistically confirmed data, the average value is, the mean square error value is, if the value of the data is within the range of (-) ~ (), then the guaranteed mean square error rate is: /m. 12-2.3-2 Mapping method
a, take a comprehensive look at the vertical distribution curves of sound velocity of each station in the sea area, and summarize them into several types; use broken lines to approximate the vertical distribution curves of sound velocity of each station according to the proposed type, find out the depth value (m) and sound velocity value (C) of each line segment connection point, and calculate the gradient value () of each line segment; C. On the base map of the sea area, put the vertical distribution element values of sound velocity of each station: that is,
21,2,Zg****+2
G, Gh-..Ge
marked at the lower right of the station,
marked the stations of the same type with broken lines to form type zones, and marked the type codes with Roman numerals in the zones: d.
eCalculate the statistical mean, mean square error and mean square error guarantee rate of Z, 2.e\G, in each type zone respectively, and list them with the attached figure.
12.3 Mathematical fitting of vertical distribution of sound velocity
Describe the measured vertical distribution curve of sound velocity required for sound field calculation as a suitable function, and allow the mathematical fitting error not to exceed ±0.2m/s.
Use cubic spline function to simulate the measured distribution curve; a
The vertical distribution curve of deep-sea sound channels can be simulated by the following formula: C() = Cmn(1 + [e - (1 - ))
Where; Cmlr
Sound velocity on the channel axis, m/s
Magnitude of deviation from Cman:
n 2(zZa)/B;
Depth of the channel axis,;
Effective width of the channel, cut.
12.4 Contents of the survey report
Introduction to the survey area, date, and implementation of the mission; b.
Measurement method, evaluation of measurement error;
GB 12763, 5--91
Overview of the distribution of sound velocity in the sea area and its changes: the main survey results that can provide services for the development of marine technology, maritime military activities and marine scientific research in the sea area; d.
Part III Measurement of marine environmental noise
13 Terms. Symbols, units
13.1 Marine environmental noise
Noise radiated by various noise sources existing in the ocean and propagated in it. 13.2 Noise band sound pressure level
The common logarithm of the ratio of the sound pressure of marine environmental noise in a certain frequency band to the reference sound pressure multiplied by 20. L = 20 lg(P,/P.)
Wherein, L
Noise band sound pressure level, dB:
The sound pressure of the noise measured by a filter (or weighting network) with a certain bandwidth, uPa; the reference sound pressure is equal to 1 μPa,
The linear broadband sound pressure level is recorded as L,; the A-weighted broadband sound pressure level is recorded as L. 13.3 Noise sound pressure spectrum level
The common logarithm of the ratio of the noise sound pressure spectrum density at a certain frequency to the reference spectrum density multiplied by 20. The spectral density of the reference sound in the ocean is 1 μPa/ /H. When the sound energy is evenly distributed in the atmosphere, - I — 10 lg4f
Wherein:
Noise sound pressure spectrum level, dB;
LThe frequency band sound pressure level measured by a bandpass filter with a center frequency of tt, dB; f—The effective bandwidth of the bandpass filter, Hz. 13.4 Background interference noise
Equivalent interference noise that interferes with the measurement due to various reasons. 13.5 Hydrophone equivalent noise sound pressure spectrum level
The common logarithm of the ratio of the hydrophone equivalent noise sound pressure spectrum density to the reference sound spectrum density multiplied by 20, in dB. 13.6Wcn2 noise spectrum level lower limit
is the lowest limit spectrum level of the ocean environmental noise drawn in the Wcn2 spectrum level diagram. 14 Technical requirements
14. 1 Main quantities to be measured
14.1.1 Sound pressure level in noise frequency band
14.1.2 Sound pressure spectrum level of noise
14.2 Auxiliary quantities to be measured
14.2.1 See GB12763.3 for wind speed, wind direction and rainfall. 14.2.2 See GB12763.2 for sea conditions, waves and currents. 14.2.3 See GB 12763.2 for vertical distribution of water depth and water temperature. 14.2.4 Seabed quality
14.2.5 See GB for the presence of ships and other sound-making organisms near the measuring station. 12763.6. The above parameters can be measured as required. 14.3 Accuracy of measurement
The uncertainty of the sound pressure level in the noise band and the sound pressure spectrum level is within the range of 4°C. -(2)
15 Technical indicators of measuring equipment
15.1 Sound transducer system
15.1.7 Measuring hydrophone (with pre-ignition device) a.
GB 12763. 591
Free field sensitivity is not less than -184 dB, reference 1 V/uPa:The superposition of the equivalent noise of the hydrophone and the noise of the preamplifier is close to the lower limit of the Wcnz noise; b.
Within the measurement frequency range, the non-uniformity of the free field sensitivity is within ±2 dB; the deviation of the horizontal directivity diagram from the ideal non-directivity diagram is within ±2 dB below the frequency of 20 kHz; d.
The vertical directivity is below the frequency of 20 kHz, and the beam width is greater than 60°. Other electroacoustic properties shall comply with the relevant provisions of the national standard GB4128 "Standard Hydrophone". 15.1.2 Structure and layout of the acoustic measurement system
The support structure should not cause resonance in the water flow, affect the sound field and form an acoustic shielding effect: soft and thin cables should be used for signal transmission, h.
The fastening of the hydrophone should be anti-vibration;
d. The self-noise interference can be estimated during measurement. This standard recommends the use of a simple acoustic measurement system, see Appendix B. 15.2 Measuring amplifier
Accuracy: ±0.2dB
Frequency range: 20Hz20kHz;
Gain: 60 dB, adjustable in steps.
15.3 Tape recorder
Frequency range, 20 Hz～20kHz;
Frequency response unevenness: ±3dB,
Signal-to-noise ratio: 40dB.
According to different requirements of noise measurement, the frequency range can be recorded in segments. 15.4 Spectrum analysis system
15.4.1 Filter
The bandpass filter used in spectrum analysis shall comply with the provisions of national standard GB3241. Other types of spectrum analysis methods (such as FFT, etc.) may also be used.
15.4.2 Display and recording
The display can be in analog or digital mode. The displayed quantity must be the root mean square value of the measured noise time process, in ft. a. Analog mode
When using a sound level recorder or an electric meter to indicate the reading, the performance of the instrument indication part shall meet the requirements of the national standard GB3785 Sound Level Meter. The instrument has a time constant of 1 to 100 s. h. Digital mode
When using a digital recorder, both linear and exponential averaging modes can be used. For digital filters, the linear averaging mode time is 0.1 to 100 s and can be selected as needed; the exponential averaging mode should be selected with a mean square error of less than 1 dB and a confidence level of 68% as the selection index. c. FFT analysis
Take more than 100 samples for averaging.
16 Observation method
The measurement hydrophone with a preamplifier converts the ocean environmental noise into an electrical signal, which is sent to a tape recorder through the measuring amplifier to store the original data samples for use in the laboratory for spectrum analysis. 16.1 Requirements for station layout and measurement environment GB 12763. 5-91
16.1.1 According to the date and requirements of the measurement, the observation station shall be arranged. 16.1.2 Requirements for measurement environment
When using survey ships or other vessels to measure marine environmental noise at sea, the station should be located more than 1 km from the shore and avoid seabed pits and obstacles.
16. 2 Measurement requirements
After the survey ship enters the station, it drops anchor and deploys the sound transducer system according to the following requirements: 16. 2. 1
The sound transducer system needs to be more than 50 m away from the ship;
The hydrophone is 5~10 m away from the sea surface.
Check whether the observation instruments are working properly.
During the measurement period, the main engine and auxiliary engine cannot be started to avoid the sound generated by human activities from being transmitted into the sea. 16-2.3
The measuring instrument shall be powered by direct current.
Adjust the gain of the measuring amplifier to prevent the measuring system from overloading. 16.2. 5
16.2.6While measuring the ocean environmental noise, observe the wind speed and direction. 16.2.7During the measurement process, pay attention to listening for any strange sounds (such as biological noise, etc.), and monitor the surrounding environment for any ships. 16.2. 8Before shutting down the auxiliary engine, measure other required ocean environmental parameters. 16.3Observation time
16.3.1Each measuring station shall be observed for at least 25 hours.
16.3.2Observe once every 1~2 hours, and each observation time is 2~~3 minutes. 16.4Contents to be recorded on site
For the format of on-site records, see Appendix A2.
16.5 Spectrum Analysis
The recorded bands of the marine scene are replayed in the laboratory and sent to the analog spectrum analyzer or digital spectrum analyzer to measure the frequency band sound pressure level of the marine environmental noise:
16.5.1 Analysis time
: The analysis time of broadband noise observation
must be more than 10 times the time constant of the measuring instrument. b. Observation of 1/3 octave filter
When the center frequency is less than 160Hz, the analysis time shall be at least 30s; when the center frequency is greater than 200Hz, the analysis time shall be at least 10s. c. Digital filter multi-channel automatic observation
The selection of analysis time shall be adapted to the analysis bandwidth, that is, the product of analysis time and bandwidth shall not be less than 100. When the analysis time is greater than 16, the analysis results of digital quantity and analog quantity are consistent. 16.5.2 To inspect and identify the type and form of marine environmental noise, the time constant "slow gear" measurement value can be compared with the "pulse" measurement value. If the difference between the two is greater than 5 dB, the noise is considered to be pulsed.
The time constant can be greater than 100 to observe the observation data in segments. If the measurement indicates that the swing deviation exceeds ±2 dB, it is considered that the noise process is more obviously non-stationary. 17 Data Arrangement
17.1 Data Processing
17.1.1 First, make necessary corrections and conversions to the measured data according to the unevenness of the measurement system. Analog quantity conversion formula:
L = A - 40 - Gu - Gs - Gs - G, r M-(4)
Conversion formula for digital multi-channel spectrometer:
GB 12763. 5-91
L = A, — 120 — Gzj — Gg -- G - M,(4)(5)In the formula, Abzxz.net
is the reading of the sound level recorder or the average value of the reading of the digital multi-channel spectrometer, B: Gu is the gain of the spectrometer, dB
Ga is the recording and playback gain of the tape recorder, dB;
-the gain of the measuring amplifier, dB;
-the gain of the preamplifier, dB
Mf -—the sensitivity of the hydrophone, dB Reference 1 V/μPa Footnote j represents the center buccal frequency of the i-th channel. 17.1.2 In order to reduce the influence of interference noise on the measurement, the following correction should be made: - Lo — t
Corrected frequency band sound pressure level, dB
Measured frequency band sound pressure level, dB;
--·Correction value, dB.
The correction value of the interference noise level is shown in the table. The △L in the table is given by the formula: AL= Lua- Lu
Measurement system interference noise level, dB.
Measurement invalid
Interference noise level correction table
Calculate the required noise sound pressure spectrum level L according to formula (1) and (2) 17.1.3
--(5)
(6)
Draw a chart of the noise sound pressure spectrum level based on the relationship between the noise sound pressure spectrum level and the frequency, and indicate the relevant environmental factors. When processing data, the content that needs to be recorded can be in accordance with GB12763.7. Contents of the survey report
Date, time and location of the sea area (latitude and longitude) of the measurement: h.
Brief description of the measurement hydrophone and its system structure and performance: Graph of the measured noise sound pressure spectrum level and the corresponding environmental conditions and instructions for the measurement; if linear regression is performed according to the same environmental factors (such as wind speed), the number of samples and the degree of dispersion must be indicated: Analysis and discussion of the measurement results.
Chapter 4 Measurement of seabed acoustic characteristics
19 Terms, symbols, units
18.1 Sediment sound velocity
The speed at which a compression (sound) wave passes through sediment. Symbol: C,
Unit: m/s
18.2 Sediment sound attenuation coefficient
The number of decibels attenuated per unit distance when a plane sound wave propagates in sediment. Symbol: &
19 Technical requirements
Unit: dB/m
19.1 The most important quantity to be measured
Vertical distribution of sediment velocity;
Sediment attenuation coefficient.
19.2 Auxiliary quantities to be measured
Vertical distribution of sediment density:
Vertical distribution of seawater sound velocity;
Median particle size of sediment particles:
Sediment particle density
Sediment porosity:
Sediment type!
Water depth, conditions.
19.3 Measurement Technical Indicators
GB 12763. 5-91
Sediment sound velocity measurement range 1 400~1900m/s Accuracy better than ±3%. 20 Measurement methods
This standard lists three measurement methods with different application scopes. The direct method is accurate and intuitive, but the measurement depth is shallow. The field measurement depth is less than 2m, and the sample laboratory is only a few meters; the reflection method and refraction method can measure the depth of tens of meters, and measure the average sound velocity of each layer. However, the observation and data processing work is large. Although the empirical method is simpler, the maximum measurement depth is 20m, but the data accuracy is poor. The surveyor can choose one or more methods according to the needs.
20.1 Indirect method
20.1.1 Principle of measurement
The direct method is to measure the time it takes for the sound wave to pass through a fixed distance of sediment to determine its sound velocity, and measure the attenuation of the sound energy at this distance to determine its attenuation coefficient. Direct methods are divided into field measurement methods and laboratory sample measurement methods. 20.1.2 Instruments and equipment
20.1.2.1 Field measurement method
Instruments for field measurement of acoustic characteristics of sediments. The accuracy of sound velocity measurement is better than ±15 m/s; a.
b. Sediment sample sampling equipment, sampling depth greater than 0.5 m; c. Seawater sound velocity meter or temperature depth meter.
20.1.2.2 Laboratory measurement method
Sediment sample sampling equipment, sample length greater than 0.5 m, sample structure is not damaged: sample splitting equipment;
Laboratory measurement of sample acoustic parameters equipment, sound velocity measurement accuracy better than ±5 m/s; c.
Seawater sound velocity meter or temperature depth meter.
20.1.3 Test requirements
Station layout principles and environmental requirements
20. 1. 3. 1
The sedimentary structure of the sampling station should be representative; the sea level should be below level 3 for offshore work. 20.1.3.2 Offshore measurement requirements
Before measuring the sound velocity, the field measuring instrument must be calibrated for the sound path, and the accuracy of the sound path calibration should be better than 0.1%; for the measurement of acoustic parameters of laboratory samples, it must be ensured that the original state of the samples is not damaged during sampling, sub-sampling and transportation; b.
For field measurement, the sediment sample should be described on site and the sediment density should be measured on board, while for laboratory measurement, e
these two tasks should be carried out after the sound velocity of the sample is measured. 20.1.4 Observation record content
The content of the field observation record is shown in Appendix A3; Field description of columnar samples,
20.2 Reflection method and refraction method
20.2.1 Measurement principle
G 12763- 5—91
Measure the propagation time of the direct wave, reflected wave and first wave at different water distances, and calculate the sound velocity and thickness of each layer in the bottom according to the law of refraction. The attenuation coefficient of each layer of sediment can be determined by the propagation path and sound energy difference between the self-arriving wave and the reflected wave. 20.2.2 Instruments and equipment
Hydrophone 200 Hz～10kHz unevenness within ±5 dB; Sound source Explosion sound source or other artificial sound source; Measuring amplifier 200Hz～10kHz unevenness ±3dB: Tape or paper tape recorder tape speed error is less than 0.2%; Oscilloscope memory oscilloscope growth oscilloscope! The delay of the radio signal transmitter is less than 2s; f
Seawater sound velocity meter or temperature depth meter.
Measurement requirements
See 20.1.3.120.2.3.1
Test requirements
20. 2. 3.2
Measure the propagation time of the direct wave, reflected wave and first wave at a horizontal distance of 1.5 to 15 times the water depth (shallow sea) from the receiving ship at least at 10 different distances: the measurement error during propagation is less than 0.5%: b.
Adjust the gain of the amplifier according to the different transmitting points to avoid overloading the channel recording the reflected wave or too weak signal; for each sound source transmitting point, there should be at least one complete echo record; c.
d. In order to make the starting point of the first wave easy to distinguish, the channel recording the first wave should be amplified by 10 sieves more than the channel recording the reflected wave; the accuracy of seawater sound velocity measurement should reach the second-level standard. e.
20.2.4 Observation record content
In addition to recording the received signal into the tape (or paper tape) recorder, the data to be recorded are shown in Appendix ^420.3 Empirical method
20.3.1 Measurement principle
The porosity and median particle size of the sediment obtained by sample analysis are used to calculate the sound velocity according to the empirical formula. 20.3.2 Instruments and equipment
Sediment sampling equipment
Sample sorting equipment;
20. 1. 2. 2 (a);
c Analysis equipment for particle size parameters, porosity, density, etc. d
Seawater sound velocity meter or temperature depth meter.
21 Data Arrangement
21.1 Direct Method
Data obtained from field or experimental measurements can be directly calculated by microcomputer program to give the vertical distribution curve of sediment sound velocity with depth.
21.1.2 The total sound reduction coefficient is calculated from the sound signal amplitude at two different fixed distances measured by the instrument. The formula is = 20 ig(A/A1)/(t2 — Ln)
Where A--the sound pressure amplitude measured at a fixed distance i (m), uPa: A, the sound pressure amplitude measured at a fixed distance L (m) [.i: Pa. 21.2 Reflection and Refraction Methods
21.2.1 There are many methods for calculating sound velocity using the reflection method and the refraction method. When the sediment sound velocity is a non-decreasing number with depth, the calculation method in Appendix C can be used as a reference.
When processing data, please note:
GB 12763. 591
: The horizontal distance R from the sound source to the hydrophone, the depth H of the hydrophone and the depth of the sound source should be solved according to the vertical distribution of the sound speed of the seawater from the propagation time of the direct sound and the seabed and sea surface reflected sound. II. The error of R should be less than 0.5%, and the error of Ht and H, should be less than 1m (shallow sea);
The reflection method and refraction method data at the same station should be calibrated to II. Ht and H, are constants respectively. 21.2.2 The sound attenuation coefficient can be calculated according to the following steps: Determine the propagation path of the reflected wave in the seabed from the solved vertical distribution of the seabed sound speed: A,
According to the vertical distribution of the sound speed of the seawater and the seabed, calculate the difference in propagation attenuation caused by refraction and reflection b.
of the direct wave and the reflected wave on different propagation paths. In the observed values of direct sound and reflected sound energy, this part of the propagation loss is deducted; e. The corrected sound energy attenuation divided by the distance is the sound attenuation coefficient. 21.3 Empirical method
According to the porosity and the particle size of the sample (), the sound velocity is calculated by the following empirical formula. For high sound velocity ratio avoidance area (commonly less than 200 m shelf) C, -\ 2 502 — 23. 45 # + 0. 14 ㎡0, —1 610 * 13. 0 M()
For low sound velocity ratio sea area (commonly found in sea areas with a depth greater than 200m) b.
, -2 506 27. 58 x + 0. 186 8 C.
Sound velocity of sediment + m/s:
Equation center. —
1 989. 26 — 138.38 md() + 10. 29 fi()Porosity of sediment, molten;
Md(s）
Median particle size of sediment.
21.4Fill in the report
Fill in the report format specified in GB12763.7. 21.5Drawing of maps
The distribution map shall be drawn according to the following requirements:
The ordinate is the depth, and the abscissa is the sound velocity or sound attenuation coefficient; b.
Select a certain scale according to the map size requirements. 21.6 Contents of the survey report,
Measurement period, sea area, station location;
Description of the measurement process;
Overview of the measurement method and measurement system;
Measurement data, curve charts:
Results of data analysis;
Discussion of the results.
Part V Measurement of sound energy propagation loss in the ocean 22 Terms, symbols and units
22.1 Energy flux density
The integral of the instantaneous sound intensity measured at a distance from the sound source over time. E(r)
I(tdt = (I/ pc)
（12)
+(13 )The depth of the sample in the laboratory is only a few meters; the reflection method and refraction method can measure up to tens of meters, and the average sound velocity of each layer is measured. However, the observation and data processing work is very laborious. Although the empirical method is simpler, the maximum depth of the layer can be measured is 20m, but the data accuracy is poor. The surveyor can choose one or more methods according to the needs.
20.1 Indirect method
20.1.1 Principle of measurement
The direct method is to measure the time it takes for the sound wave to pass through a fixed distance of sediment to determine its sound velocity, and measure the attenuation of the sound energy at this distance to determine its attenuation coefficient. The direct method is divided into field measurement method and laboratory sample measurement method. 20.1.2 Instruments and equipment
20.1.2.1 Field measurement method
Field measurement instrument for sediment acoustic characteristics. The sound velocity measurement accuracy is better than 15 m/s; a.
b. Sediment sampling equipment, sampling depth greater than 0.5m; C. Seawater sonic velocity meter or temperature depth meter.
20.1.2.2 Laboratory measurement method
Sediment sampling equipment, sample length greater than 0.5m, sample structure not damaged: Sample splitting equipment;
Laboratory equipment for measuring acoustic parameters of samples, sound velocity measurement accuracy better than ±5m/s; c. Seawater sonic velocity meter or temperature depth meter.
20.1.3 Test requirements
Station layout principles and environmental requirements
20. 1. 3. 1
The sedimentary structure of the sampling station should be representative; the sea level for offshore work should be below level 3. 20.1.3.2 Requirements for offshore measurements
Before measuring the sound velocity, the field measuring instrument must be calibrated for the sound path, and the accuracy of the sound path calibration should be better than 0.1%; for the measurement of acoustic parameters of laboratory samples, it must be ensured that the original state of the samples is not damaged during sampling, sub-sampling and transportation; b.
For field measurements, the sediment type description and sediment density determination of the sediment samples should be carried out on board, while for laboratory measurements, these two tasks should be carried out after the sound velocity determination of the samples. 20.1.4 Contents of observation records
For the contents of field observation records, see Appendix A3 Table; Field description of columnar samples,
20.2 Reflection method and refraction method
20.2.1 Principle of measurement
G 12763- 5—91
Measure the propagation time of the direct wave, reflected wave and head wave at different water distances, and calculate the sound velocity and thickness of each layer in the bottom according to the law of refraction. The attenuation coefficient of each layer of sediment can be determined by the propagation path and sound energy difference between the self-arriving wave and the reflected wave. 20.2.2 Instruments and Equipment
Hydrophone 200 Hz ~ 10kHz unevenness within ± 5 dB; sound source explosion sound source or other artificial sound source; measurement amplifier 200Hz ~ 10kHz unevenness ± 3dB: tape or paper tape recorder tape speed error less than 0.2%; oscilloscope memory oscilloscope growth oscilloscope! Radio signal transmitter delay less than 2s; f
Seawater sound velocity meter or temperature depth meter.
Measurement requirements
For station layout and environmental requirements, see 20.1.3.120.2.3.1
Measurement requirements
20. 2. 3.2
The propagation time of the direct wave, reflected wave and first wave should be measured at at least 10 different distances within the horizontal distance of 1.5 to 15 times the water depth (shallow sea) from the receiving ship: the measurement error during propagation is less than 0.5%: b.
The gain of the amplifier should be adjusted according to the different emission points to avoid overloading the channel recording the reflected wave or too weak signal; for each sound source emission point, there should be at least one complete echo record; c.
d. In order to make the starting point of the first wave easy to distinguish, the channel recording the first wave should be amplified by 10 screens more than the channel recording the reflected wave; the accuracy of seawater sound velocity measurement should reach the second-level standard. e.
20.2.4 Observation record contents
In addition to recording the received signal into a tape (or paper tape) recorder, the data to be recorded are shown in Appendix ^4. 20.3 Empirical method
20.3.1 Measurement principle
The porosity and median particle size of the sediment obtained by sample analysis are used to calculate the sound velocity according to the empirical formula. 20.3.2 Instruments and equipment
Sediment sampling equipment
Sample sorting equipment;
20. 1. 2. 2 (a);
cAnalysis equipment for particle size parameters, porosity, density, etc. d
Seawater sound velocity meter or temperature depth meter.
21 Data collation
21.1 Direct method
The data obtained from field or experimental measurements can be directly calculated by a microcomputer program to give a vertical distribution curve of sediment sound velocity with depth.
21.1.2 The total acoustic reduction coefficient is calculated from the acoustic signal amplitude at two different fixed distances measured by the instrument. The formula is = 20 ig(A/A1)/(t2 — Ln)
Wherein, A is the sound pressure amplitude measured at a fixed distance i (m), uPa: A, and the sound pressure amplitude measured at a fixed distance L (m) is uPa. 21.2 Reflection method and refraction method
21.2.1 There are many methods for calculating the sound velocity by reflection method and refraction method. When the sound velocity of sediment is a non-decreasing number with depth, the calculation method in Appendix C can be used as a reference.
When processing data, it is necessary to pay attention to the following:
GB 12763. 591
: The horizontal distance R from the sound source to the hydrophone and the depth H of the hydrophone should be solved according to the vertical distribution of the sound velocity of seawater by the propagation time of the direct sound and the seabed and the reflected sound on the sea surface. The error of the depth of the sound source II, R should be less than 0.5%, and the error of Ht, H, should be less than 1m (shallow sea);
The reflection method and refraction method data at the same station should be calibrated to II. , H, are constants respectively. 21.2.2 The sound attenuation coefficient can be calculated according to the following steps: Determine the propagation path of the reflected wave in the seabed by the solved vertical distribution of the seabed sound velocity: A,
According to the vertical distribution of the sound velocity of the seawater and the seabed, calculate the difference in propagation attenuation caused by refraction and reflection b.
on different propagation paths between the direct wave and the reflected wave. In the observed values of the sound energy of the direct sound and the reflected sound, deduct this part of the propagation attenuation difference; e, the corrected sound energy attenuation divided by the distance is the sound attenuation coefficient. 21.3 Empirical method
According to the porosity and the medium particle size () of the test sample, the sound velocity is calculated by the following empirical formula. For high sound velocity ratio avoidance area (commonly found in the continental shelf with depth less than 200 m) C, -\ 2 502 — 23. 45 # + 0. 14 ㎡0, —1 610 * 13. 0 M()
For low sound velocity ratio sea area (commonly found in the sea area with depth greater than 200 m) b.
, -2 506 27. 58 x + 0. 186 8 C.
Sound velocity of sediment +m/s:
center of equation. —
1 989. 26 — 138.38 md() + 10. 29 fi()Porosity of sediment, molten;
Md(s)
Median particle size of sediment.
21.4 Fill in the report
Fill in the report format specified in GB12763.7. 21.5 Drawing
The distribution map should be drawn according to the following requirements:
The vertical axis is depth, and the horizontal axis is sound velocity or sound attenuation coefficient; b.
Select a certain scale according to the map size requirements. 21.6 Contents of the survey report,
Measurement period, sea area, and station;
Description of the measurement process;
Overview of the measurement method and measurement system;
Measurement data, curve charts:
Results of data analysis;
Discussion of the results.
Chapter 5 Measurement of sound energy propagation loss in the ocean 22 Terms, symbols and units
22.1 Energy flux density
The integral of the instantaneous sound intensity measured at a distance from the sound source over time. E(r)
I(tdt = (I/ pc)
（12)
+(13 )The depth of the sample in the laboratory is only a few meters; the reflection method and refraction method can measure up to tens of meters, and the average sound velocity of each layer is measured. However, the observation and data processing work is very laborious. Although the empirical method is simpler, the maximum depth of the layer can be measured is 20m, but the data accuracy is poor. The surveyor can choose one or more methods according to the needs.
20.1 Indirect method
20.1.1 Principle of measurement
The direct method is to measure the time it takes for the sound wave to pass through a fixed distance of sediment to determine its sound velocity, and measure the attenuation of the sound energy at this distance to determine its attenuation coefficient. The direct method is divided into field measurement method and laboratory sample measurement method. 20.1.2 Instruments and equipment
20.1.2.1 Field measurement method
Field measurement instrument for sediment acoustic characteristics. The sound velocity measurement accuracy is better than 15 m/s; a.
b. Sediment sampling equipment, sampling depth greater than 0.5m; C. Seawater sonic velocity meter or temperature depth meter.
20.1.2.2 Laboratory measurement method
Sediment sampling equipment, sample length greater than 0.5m, sample structure not damaged: Sample splitting equipment;
Laboratory equipment for measuring acoustic parameters of samples, sound velocity measurement accuracy better than ±5m/s; c. Seawater sonic velocity meter or temperature depth meter.
20.1.3 Test requirements
Station layout principles and environmental requirements
20. 1. 3. 1
The sedimentary structure of the sampling station should be representative; the sea level for offshore work should be below level 3. 20.1.3.2 Requirements for offshore measurements
Before measuring the sound velocity, the field measuring instrument must be calibrated for the sound path, and the accuracy of the sound path calibration should be better than 0.1%; for the measurement of acoustic parameters of laboratory samples, it must be ensured that the original state of the samples is not damaged during sampling, sub-sampling and transportation; b.
For field measurements, the sediment type description and sediment density determination of the sediment samples should be carried out on board, while for laboratory measurements, these two tasks should be carried out after the sound velocity determination of the samples. 20.1.4 Contents of observation records
For the contents of field observation records, see Appendix A3 Table; Field description of columnar samples,
20.2 Reflection method and refraction method
20.2.1 Principle of measurement
G 12763- 5—91
Measure the propagation time of the direct wave, reflected wave and head wave at different water distances, and calculate the sound velocity and thickness of each layer in the bottom according to the law of refraction. The attenuation coefficient of each layer of sediment can be determined by the propagation path and sound energy difference between the self-arriving wave and the reflected wave. 20.2.2 Instruments and Equipment
Hydrophone 200 Hz ~ 10kHz unevenness within ± 5 dB; sound source explosion sound source or other artificial sound source; measurement amplifier 200Hz ~ 10kHz unevenness ± 3dB: tape or paper tape recorder tape speed error less than 0.2%; oscilloscope memory oscilloscope growth oscilloscope! Radio signal transmitter delay less than 2s; f
Seawater sound velocity meter or temperature depth meter.
Measurement requirements
For station layout and environmental requirements, see 20.1.3.120.2.3.1
Measurement requirements
20. 2. 3.2
The propagation time of the direct wave, reflected wave and first wave should be measured at at least 10 different distances within the horizontal distance of 1.5 to 15 times the water depth (shallow sea) from the receiving ship: the measurement error during propagation is less than 0.5%: b.
The gain of the amplifier should be adjusted according to the different emission points to avoid overloading the channel recording the reflected wave or too weak signal; for each sound source emission point, there should be at least one complete echo record; c.
d. In order to make the starting point of the first wave easy to distinguish, the channel recording the first wave should be amplified by 10 screens more than the channel recording the reflected wave; the accuracy of seawater sound velocity measurement should reach the second-level standard. e.
20.2.4 Observation record contents
In addition to recording the received signal into a tape (or paper tape) recorder, the data to be recorded are shown in Appendix ^4. 20.3 Empirical method
20.3.1 Measurement principle
The porosity and median particle size of the sediment obtained by sample analysis are used to calculate the sound velocity according to the empirical formula. 20.3.2 Instruments and equipment
Sediment sampling equipment
Sample sorting equipment;
20. 1. 2. 2 (a);
cAnalysis equipment for particle size parameters, porosity, density, etc. d
Seawater sound velocity meter or temperature depth meter.
21 Data collation
21.1 Direct method
The data obtained from field or experimental measurements can be directly calculated by a microcomputer program to give a vertical distribution curve of sediment sound velocity with depth.
21.1.2 The total acoustic reduction coefficient is calculated from the acoustic signal amplitude at two different fixed distances measured by the instrument. The formula is = 20 ig(A/A1)/(t2 — Ln)
Wherein, A is the sound pressure amplitude measured at a fixed distance i (m), uPa: A, and the sound pressure amplitude measured at a fixed distance L (m) is uPa. 21.2 Reflection method and refraction method
21.2.1 There are many methods for calculating the sound velocity by reflection method and refraction method. When the sound velocity of sediment is a non-decreasing number with depth, the calculation method in Appendix C can be used as a reference.
When processing data, it is necessary to pay attention to the following:
GB 12763. 591
: The horizontal distance R from the sound source to the hydrophone and the depth H of the hydrophone should be solved according to the vertical distribution of the sound velocity of seawater by the propagation time of the direct sound and the seabed and the reflected sound on the sea surface. The error of the depth of the sound source II, R should be less than 0.5%, and the error of Ht, H, should be less than 1m (shallow sea);
The reflection method and refraction method data at the same station should be calibrated to II. , H, are constants respectively. 21.2.2 The sound attenuation coefficient can be calculated according to the following steps: Determine the propagation path of the reflected wave in the seabed by the solved vertical distribution of the seabed sound velocity: A,
According to the vertical distribution of the sound velocity of the seawater and the seabed, calculate the difference in propagation attenuation caused by refraction and reflection b.
on different propagation paths between the direct wave and the reflected wave. In the observed values of the sound energy of the direct sound and the reflected sound, deduct this part of the propagation attenuation difference; e, the corrected sound energy attenuation divided by the distance is the sound attenuation coefficient. 21.3 Empirical method
According to the porosity and the medium particle size () of the test sample, the sound velocity is calculated by the following empirical formula. For high sound velocity ratio avoidance area (commonly found in the continental shelf with depth less than 200 m) C, -\ 2 502 — 23. 45 # + 0. 14 ㎡0, —1 610 * 13. 0 M()
For low sound velocity ratio sea area (commonly found in the sea area with depth greater than 200 m) b.
, -2 506 27. 58 x + 0. 186 8 C.
Sound velocity of sediment +m/s:
center of equation. —
1 989. 26 — 138.38 md() + 10. 29 fi()Porosity of sediment, molten;
Md(s)
Median particle size of sediment.
21.4 Fill in the report
Fill in the report format specified in GB12763.7. 21.5 Drawing
The distribution map should be drawn according to the following requirements:
The vertical axis is depth, and the horizontal axis is sound velocity or sound attenuation coefficient; b.
Select a certain scale according to the map size requirements. 21.6 Contents of the survey report,
Measurement period, sea area, and station;
Description of the measurement process;
Overview of the measurement method and measurement system;
Measurement data, curve charts:
Results of data analysis;
Discussion of the results.
Chapter 5 Measurement of sound energy propagation loss in the ocean 22 Terms, symbols and units
22.1 Energy flux density
The integral of the instantaneous sound intensity measured at a distance from the sound source over time. E(r)
I(tdt = (I/ pc)
（12)
+(13 )1 Field measurement method
Field measurement instruments for acoustic properties of sediments. The accuracy of sound velocity measurement is better than ±15 m/s; a.
b. Sediment sampling equipment, sampling depth greater than 0.5 m; c. Seawater sound velocity meter or temperature depth meter.
20.1.2.2 Laboratory measurement method
Sediment sampling equipment, sample length greater than 0.5 m, sample structure not damaged: sample splitting equipment;
Laboratory equipment for measuring acoustic parameters of samples, sound velocity measurement accuracy better than ±5 m/s; c.
Seawater sound velocity meter or temperature depth meter.
20.1.3 Test requirements
Station layout principles and environmental requirements
20. 1. 3. 1
The sedimentary structure of the sampling station should be representative; the sea level should be below level 3 for offshore work. 20.1.3.2 Offshore measurement requirements
Before measuring the sound velocity, the field measuring instrument must be calibrated for the sound path, and the accuracy of the sound path calibration should be better than 0.1%; for the measurement of acoustic parameters of laboratory samples, it must be ensured that the original state of the samples is not damaged during sampling, sub-sampling and transportation; b.
For field measurement, the sediment sample should be described on site and the sediment density should be measured on board, while for laboratory measurement, e
these two tasks should be carried out after the sound velocity of the sample is measured. 20.1.4 Observation record content
The content of the field observation record is shown in Appendix A3; Field description of columnar samples,
20.2 Reflection method and refraction method
20.2.1 Measurement principle
G 12763- 5—91
Measure the propagation time of the direct wave, reflected wave and first wave at different water distances, and calculate the sound velocity and thickness of each layer in the bottom according to the law of refraction. The attenuation coefficient of each layer of sediment can be determined by the propagation path and sound energy difference between the self-arriving wave and the reflected wave. 20.2.2 Instruments and equipment
Hydrophone 200 Hz～10kHz unevenness within ±5 dB; Sound source Explosion sound source or other artificial sound source; Measuring amplifier 200Hz～10kHz unevenness ±3dB: Tape or paper tape recorder tape speed error is less than 0.2%; Oscilloscope memory oscilloscope growth oscilloscope! The delay of the radio signal transmitter is less than 2s; f
Seawater sound velocity meter or temperature depth meter.
Measurement requirements
See 20.1.3.120.2.3.1
Test requirements
20. 2. 3.2
Measure the propagation time of the direct wave, reflected wave and first wave at a horizontal distance of 1.5 to 15 times the water depth (shallow sea) from the receiving ship at least at 10 different distances: the measurement error during propagation is less than 0.5%: b.
Adjust the gain of the amplifier according to the different transmitting points to avoid overloading the channel recording the reflected wave or too weak signal; for each sound source transmitting point, there should be at least one complete echo record; c.
d. In order to make the starting point of the first wave easy to distinguish, the channel recording the first wave should be amplified by 10 sieves more than the channel recording the reflected wave; the accuracy of seawater sound velocity measurement should reach the second-level standard. e.
20.2.4 Observation record content
In addition to recording the received signal into the tape (or paper tape) recorder, the data to be recorded are shown in Appendix ^420.3 Empirical method
20.3.1 Measurement principle
The porosity and median particle size of the sediment obtained by sample analysis are used to calculate the sound velocity according to the empirical formula. 20.3.2 Instruments and equipment
Sediment sampling equipment
Sample sorting equipment;
20. 1. 2. 2 (a);
c Analysis equipment for particle size parameters, porosity, density, etc. d
Seawater sound velocity meter or temperature depth meter.
21 Data Arrangement
21.1 Direct Method
Data obtained from field or experimental measurements can be directly calculated by microcomputer program to give the vertical distribution curve of sediment sound velocity with depth.
21.1.2 The total sound reduction coefficient is calculated from the sound signal amplitude at two different fixed distances measured by the instrument. The formula is = 20 ig(A/A1)/(t2 — Ln)
Where A--the sound pressure amplitude measured at a fixed distance i (m), uPa: A, the sound pressure amplitude measured at a fixed distance L (m) [.i: Pa. 21.2 Reflection and Refraction Methods
21.2.1 There are many methods for calculating sound velocity using the reflection method and the refraction method. When the sediment sound velocity is a non-decreasing number with depth, the calculation method in Appendix C can be used as a reference.
When processing data, please note:
GB 12763. 591
: The horizontal distance R from the sound source to the hydrophone, the depth H of the hydrophone and the depth of the sound source should be solved according to the vertical distribution of the sound speed of the seawater from the propagation time of the direct sound and the seabed and sea surface reflected sound. II. The error of R should be less than 0.5%, and the error of Ht and H, should be less than 1m (shallow sea);
The reflection method and refraction method data at the same station should be calibrated to II. Ht and H, are constants respectively. 21.2.2 The sound attenuation coefficient can be calculated according to the following steps: Determine the propagation path of the reflected wave in the seabed from the solved vertical distribution of the seabed sound speed: A,
According to the vertical distribution of the sound speed of the seawater and the seabed, calculate the difference in propagation attenuation caused by refraction and reflection b.
of the direct wave and the reflected wave on different propagation paths. In the observed values of direct sound and reflected sound energy, this part
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