The method of calibration of hydroacoustic measuring path of the working measuring instruments

 

(57) Abstract:

The invention relates to underwater acoustics and can be used for metrological verification of working measuring instruments (FSW) in natural conditions. The essence of the method lies in the fact that in the known method of calibration, is the impact on the measuring paths of the working tools of measurement and the reference measurement means (ESI) test signal and comparing the results of measurements of the parameters of the test signal FSW and ESI, the results of which are calibration RCI, as the test signal, acting on the measuring paths RCI and began to use the natural noise of the marine environment. To determine the measurement errors that occur when switching limits of measurement equipment RCI, the calibration is carried out in stormy weather and (or) the period of seismic activity. Thus, in the proposed method, the calibration of the RSI is in the natural pond in the absence of special hydrosilicates, which significantly simplify and reduce the cost of the calibration process. 1 C.p. f-crystals, 1 Il.

The invention relates to the field of hydro-acoustics and can be used for calibration focused on the measurement of the transmission factor of the hydroacoustic measuring path of RCI i.e. the definition of non-uniformity of the amplitude-frequency characteristics (AFC) hydroacoustic measuring path.

Under hydroacoustic measuring path refers to a measuring instrument, intended for conversion of an acoustic signal in the aquatic environment into an electrical signal for amplification and pre-processing of this signal, and to transmit it to the final processing apparatus and reception.

There is a method similar purpose, namely, that the receiving part hydroacoustic measuring path RCI removed from his native place and transport it to the source of the test signal [1].

The disadvantage of this method is the necessity of dismantling the measuring path RCI in difficult offshore in-situ measurements and low accuracy calibration due to different operating conditions and calibration.

There is a method of calibration hydroacoustical measuring path RCI in location of the reservoir, which consists in the simultaneous influence on the measuring paths work and exemplary measuring the test signal and comparing the results Esmerelda calibration of the measuring path of the working measuring instruments [2].

This method is adopted for the prototype.

In the prototype for the implementation of the above actions at the receiving part RCI fix special hydroacoustic target with the reference force goals, which is a disadvantage of the known method. In addition, the parameters of hydroacoustic targets over time is subject to change, which will lead to more difficult to estimate the errors of the calibration of the measuring path RCI.

As in the analog, and the prototype for calibration of the RSI requires special sonar emitters on a very wide frequency range, the production of which is a big problem in underwater acoustics.

In addition, the pressure level of the excited emitter is heavily dependent on the location of the emitter in the volume of the reservoir and the distance between the points of emission and reception. For infrasonic frequencies to produce the emitter of the test signals and sonar target - the thing is insoluble. Therefore, the prototype has a fairly narrow band of frequencies on which to perform the calibration of the RSI.

The technical result from implementation of the invention is to simplify and cheapen the practical implementation of the SPO the calibration of hydroacoustic measuring path RCI in location of the reservoir, consisting in simultaneous influence on the measuring paths RCI and began the test signal and comparing the results of measurements of the parameters of the test signal FSW and ESI, the results of which carry out the calibration of the measuring path of RCI as a test signal, affecting acoustic paths RCI and began to use natural noise (natural sea water environment.

The receiving part hydroacoustic measuring paths RCI and began to feature in the aquatic environment under a layer of temperature jump so that the distance between them vertically r and horizontally l satisfy the inequalities: rH/50; lH/30, where H is the depth of the receiving part of the measuring path RCI.

The essence of this method of calibration is based on the fact that water marine environment, there is a natural hydroacoustic noise in which the main sources are [3, 4]:

- extensive seabed surface, transmitting in the thickness of the water-situ reservoir infrasound vibrations of the earth's crust seismic character (near and distant earthquakes, volcanic eruptions, tsunamis and others);

- extensive agitated water surface, the noises which are defined Devich frequencies;

- thermal noise of molecular and temperature of the nature, effects and impact of the randomly moving water molecules with the surface of the hydrophones receiving part of the measuring path RCI (Brownian motion of water molecules).

There are also marine noise "artificial" origin: noises shipping, turbulence pseudocode occur on the structures of hydrophones due to the formation of vortices and turbulent flows.

Artificial noise sources when properly designed RCI and correctly selected measuring field reservoirs become negligible compared with natural sources of noise, particularly noise sources of the sea surface, and the noise of distant shipping in the proposed method does not have a significant impact on the accuracy of the calibration.

Each wave on the surface of a pond creates acoustic pressure in water volume. Such waves on the surface of a pond lot and they are widely distributed, forming, in essence, the vast size of the noise source acoustic oscillations. Reflected from the bottom of the reservoir and inhomogeneities of the aquatic environment, they form a diffuse noise sonar sole field sound pressure level, acting on the hydrophone, in each moment of time is only weakly dependent on the location of the hydrophone, especially in the middle part of the reservoir.

Consistency (small and slow change of parameters of noise in the reservoir allows the assessment of their level analytically [5].

Numerous studies of authors and other experimenters conducted for 25 - 30 years in various areas of the seas and oceans, have shown the possibility of using the natural sound of the sea water environment for the purposes of calibration of hydroacoustic measuring path RCI.

In order to reduce the influence of variability of the noise parameters of the sea water environment on the results of the calibration requires the following conditions:

- measurement of parameters of sea noise should be carried out synchronously. The start and end of the measurement began and RCI should not vary by more than 1 sec;

- receiving part hydroacoustic measuring paths RCI and AXIS (hydrophones) must be located under a layer of temperature jump [6] as close as possible to each other;

- the size and shape of the fairings hydrophones FSW and ESI should be equal or similar.

Maximum sblizhenie each other. In any case, the distance l on horizontaly and r vertically between the hydrophones depends on the depth H of the hydrophone RCI and is given by the expression above.

The greater the depth H, the more uniform acoustic noise field and the greater the value of r and l. The vertical stratification of the marine environment determines a higher heterogeneity of the sound field vertically than horizontally. Specific values of the denominators in the inequalities rH/50; lH/30 experimentally obtained and associated with acceptable errors obtained in the calibration RCI using the proposed method.

The existing spatial-temporal instability in the aquatic environment imposes certain spatial and temporal constraints on the calibration of the RSI.

Time calibration of the RSI (time determine the amplitude-frequency response of the hydrophone in 1/3-octave band analysis with parallel frequency filters and drives) is not more than 2.5 - 3 minutes. During this time, the distance between the hydrophones will have time to change no more than H/100, which means that the inequality will remain in force. Allowing known methods to determine the amplitude-frequency characteristic (AFC) which require strict synchronization of the beginning and end of the measurement for each realization of the noise of the marine environment by transmitting the synchronization signal over the air.

Hydroacoustic measuring path RCI in addition to frequency response and error definition is also characterized by the error limit switches dimensions (scales). This error is determined in the process of determining the frequency response at different levels of the input signal (noise water environment). For example, during stormy weather and / or seismic noise signal is significantly increased and it is necessary to use a less sensitive measurement range FSW and ESI.

The invention is illustrated by the drawing, which shows a diagram of the practical implementation of the method.

The device for implementing the method comprises measuring instrument (RCI), made for example in the form of hydrophone 1, fixed at a certain point in-situ reservoir 2 through the anchor device 3, a cable 4, the float 5 positive buoyancy and the mechanical filter and devices 6 preliminary signal processing.

There is also a reference instrument (ESI), made for example in the form of hydrophone 7, pre attorney in the laboratory, fixed on the distance r, l from the hydrophone 1 RCI using surface vessels 8, the cable 9, the cargo is of hydrophone 1 RCI come through the cable 12, laid on the bottom 13 of the reservoir 2 to the coastal post measurements 14 and hydrophone 7 ESI - cable-cable 9 to the processing device 15 and the registration of which is connected to the transmitting device 16 having a transmitting antenna 17. Thus, the output signal from the ESI 7 over the air is also fed to a shore station 14 measurements with the receiving antenna 18.

The method is implemented as follows.

After you install hydrophones 1 RCI and 7 began in specific points of the in-situ reservoir 2 at the same time include their measuring paths. At both measurement circuit simultaneously and identically affects the natural noise of the in-situ reservoir 2. Outputs RCI and began to receive an electrical voltage proportional to exposure levels hydroacoustic pressure marine noise.

The voltage from the hydrophone 7 ESI is amplified and subjected to spectral and correlation processing and registration processing unit 15 and the Desk, and then using the transmitting device 16 and the transmitting antenna 17 and the air is sent to a shore station 14 measurements.

The voltage output of the hydrophone 1 RCI cable 12 is also fed to a shore station 14 measurements.

Alastriona the implementation of the AFC measuring paths FSW and ESI. By using a comparator or visual conduct the comparison of frequency responses of RCI and AFC began, and the results are mutually correlation processing is judged on the errors of calibration.

During stormy weather and(or) seismic activity such measurements are repeated for calibration of hydroacoustic measuring path RCI other limits of measurements and verify the correct operation of limit switches dimensions. Similar measurements carried out in calm.

The level of noise and interference that occurs when the vibrations FSW and ESI should be significantly lower noise of the sea.

Thus, in the present method, the calibration of the RSI is in the natural pond in the absence of special hydrosilicates, which significantly simplify and reduce the cost of the calibration process compared to the prototype. Due to the technical result.

Sources of information

1. The Japan patent N 55-28515, CL G 01 S 3/80, G 01 H 3/00, 1980.

2. RF patent N 2042283, CL H 04 R 29/00, 1995 prototype.

3. R. J. Urik. Fundamentals of hydro-acoustics. L., Shipbuilding, 1978, S. 211 - 230, S. 344 - 347.

4. A. P. Evtuhov, A. E. Kolesnikov and other Reference hydroacoustics. L., Shipbuilding, 1982, S. 42 - 52.

6. L. A. Zhukov. General Oceanography. Leningrad, Gidrometeoizdat, 1976, S. 278 - 295.

1. The method of calibration of hydroacoustic measuring path of the working measuring instruments in location of the reservoir, which consists in the simultaneous influence on the measuring paths of the working and reference measurement means test signal and comparing the results of measurements of the parameters of the test signal work and standard means of measurement, the results of which carry out the calibration of the measuring path of the working measuring instruments, characterized in that as the test signal, affecting hydroacoustic measuring paths of the working and reference measurement, use the natural sound of the sea water environment.

2. The method according to p. 1, characterized in that the receiving part hydroacoustic measuring paths of the working and reference measurement feature in the marine environment under a layer of temperature jump so that the distance between them vertically r and the horizontal l satisfy the inequalities: r H/50; l H/30, where H is the depth of the receiving part of the measuring path of the working measuring instruments.

 

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