Method of determining bearing of noisy object

FIELD: physics.

SUBSTANCE: method involves receiving an acoustic signal during "electric" rotation of the beam pattern of components x and y of a composite receiver consisting of a vector receiver and a hydrophone. The received signal undergoes analogue-to-digital conversion via Hilbert or Fourier transform with subsequent conversion of the signal into analytical form. Further, the ratio of the imaginary part of the signal to the real part is calculated and that ratio is used to estimate the phase difference between acoustic pressure p(t) and orthogonal components of particle velocity The bearing of the noisy object is identified by a phase difference jump of 180°.

EFFECT: wider operating frequency range of the method.

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The invention relates to underwater acoustics and can be used for hydroacoustic research and locate underwater and surface objects using combined acoustic receivers.

Known methods for determining the bearing to the source of the noise, such as determining the direction of sound sources in the horizontal plane (C. Of the Russian Federation No. 2002113840, IPC⁷G01S 3/00). The method is based on the reception of acoustic vibrations of two linear groups of electroacoustic transducers, converting the acoustic signals into proportional electrical signals, the measurement of these signals, determining the bearing to the sound source, using values of the electrical signals and determining the bearing to the sound source by the relationship between the measured electrical signals.

There is a method of determining the angles of bearing low-flying targets in space according to their acoustic emissions (Z. Of the Russian Federation No. 95103536, IPC⁶G01S 3/808). The method consists in the measurement of the difference of the coming phases of the acoustic waves between the spaced reception points, with the aim of obtaining a circular sector detection without mechanical movement of the receiving system, the incoming acoustic signal is measured at three fixed points in the horizontal plane located at the vertices of an equilateral treugol is nick, and by the values of the phase difference between the various reception points define the corners of bearing low-flying targets in the horizontal and vertical planes.

However, these methods have low accuracy of determination of bearing and low immunity. In addition, their implementation requires a complicated construction of the device is complicated configuration and larger receiving systems.

Closest to the claimed method is a method of determining bearing on an underwater object, emitting acoustic harmonic signal with a certain frequency (p. the Russian Federation No. 2158430, IPC G01S 3/80). The method includes the generation and emission of underwater object above signal, the signal receiver comprising at least eight hydrophones forming oriented in the horizontal plane of the circular measurement base the selection of the quadrature components of the complex envelope of the received acoustic signals and measuring their phase. The signals received by the hydrophones base, pre-phase to N directions passing through the center of the base and each of N hydrophones. Determine the direction corresponding to the maximum signal and the hydrophone, lying in this direction. The bearing to the source in the local coordinate system associated with a circular base, determined by the formula given angular coordinates of the _nhydrophones, the number of hydrophones, the cumulative phase θ_non the n-th hydrophone relative phase on the hydrophone, lying in the direction of maximum signal, i.e. the direction to the source is determined by the maximum amplitude and phase change.

The main disadvantage of this method is the requirement that radiation underwater object artificial harmonic signal and accounting when calculating bearing only the acoustic pressure and the need of a large number of hydrophones arranged in a certain way, that leads to complexity of the process, low noise immunity and accuracy.

The objective of the invention is to develop a robust method for determining the bearing on the noisy object, simplify the method and to increase its accuracy, the extension of the operating frequency range of the method, which is achieved by including in the way that both the scalar and vector information of the characteristics of the acoustic field and based on the jump of the phase difference between the acoustic pressure and horizontal components of oscillatory velocity.

The problem is solved by a method for determining bearing on noisy underwater or surface of the object, including the measurement at one point of the acoustic field at the same time the four physical quantities: three orthogonal the data component of the vector oscillating speed and the acoustic pressure p(t) using combined receiver, including vector receiver and hydrophone, converting the received signal into a digital code, translating it into an analytical form for determining the phase difference between the acoustic pressure and the orthogonal components of oscillatory velocity in an electric rotating around the z-axis of the directivity vector receiver and jump on the phase difference between the acoustic pressure p(t) and orthogonal components of oscillatory velocity V_x(t, α) and V_y(t, α) determine the bearing to the noisy object.

The method is based on the permanent electric rotating around the z-axis horizontal axes x and y coordinates of the combined receiver according to the formula

where u_xu_y- electric signals from the channels x and y, when the angle of rotation α=0,,- electric signals by rotating the coordinate azimuthal angle α.

Combo receiver is a device vklyuchayuschee vector receiver and hydrophone [Shurov Vector VA ocean acoustics. Dalnauka, 2003. 307 S.].

Leap phase difference is one of the components of oscillatory velocity or V_x(t, α), either V_y(t, α), mini is the mind of the directional characteristics of which lies on a straight line, linking combo receiver and the detected object. Thus the maximum directivity of the second components of V_y(t, α) coincides with the minimum orientation of the first component V_x(t, α).

Once installed, the sector angles α₀±Δα, in which there is a jump of the phase difference of 180°, the coordinate system x0y "wobbles" "electric" method in the angular sector α₀±Δα to determine the statistical characteristics: the average value <α₀>and its standard deviation. Angle <α₀>counted from the x-axis coincides with the direction of the noise source.

The algorithm of the method includes the following sequence of operations. Four narrow-band acoustic signal p(t, f₀), V_x(t, f₀), V_y(t, f₀), V_z(t, f₀)registered vector receiver and hydrophone, is converted into a digital code, which is in the data block is converted in analytical form using conventional mathematical transformations, such as Fourier or Hilbert:

S=S-j·Re(TH(S))

where TH(S) is the Hilbert transform of the signal S.

Calculates the ratio of the imaginary and real parts of the analytic signal to obtain the tangent of the phase:

where P(f)is the acoustic pressure, depends only on time t; V_x(t, α), V_y(t, α) is orthogonal components of oscillatory velocity that depends on time t and the azimuthal angle α; φ_p(t), φ_x(t, α), φ_y(t, α) - averaged values of phase acoustic pressure and oscillating velocity of the analytical signal. Value averaging time depends on the speed of movement of the noisy object.

The conclusion about the presence of noisy object in the given direction α₀it should jump from the phase difference between the acoustic pressure p(t) and the components of oscillatory velocity Δφ_x=φ_p- Φ_xor Δφ_y=φ_p- Φ_ywhen passing through α₀from α₀-Δα to α₀+Δα.

To improve the accuracy of direction finding are derived from Δφ_x(t, α) and Δφ_y(t, α) by angle α:,. The resulting bearing is defined as (α₀+180°)±σ_αwhere σ_α- the standard deviation.

The drawing shows the results of passive lizirovania underwater source. The source depth ≈60 m Depth combo receiver 150 m Jumps of phase difference (a) - Δφ_x(α₀, t₀), b - Δφ_y(α₀, t₀); 1 - curves correspond Δφ(α₀, t₀), Δφ_y(α₀, t₀), 2 - they are derived. Vertical lines on the curves according to testout σ _xand σ_y. The angle α is measured in degrees, the phase difference in radians. The source was located at a depth of about 60 m Combo receiver was located at a depth of 150 m, the Frequency at which was held passive lizirovania object equal 617 Hz. The analysis bandwidth Δf=3 Hz. Signal-to-noise ratio is not more than 3 dB. On the first jump of the phase difference (drawing) it follows that α₀equal to 32.5°±5,0° and the bearing to the object is equal to 212,5°±5,0°.

Thus, the inventive method allows to achieve the claimed technical result and to detect passive mode surface or underwater object by the radiation they pseudonoise signal, and not by radiation they artificially generated harmonic oscillations. The transition from the amplitude characteristic to the phase significantly increased the immunity method, since the phase difference Δφ_x(t, α) and Δφ_y(t, α) takes only two values 0° or 180°, and the transition from one value of the difference of phase to another is abrupt. In the inventive method, the direction to the source is determined only by the jump in the phase difference between the acoustic pressure and horizontal components of oscillatory velocity equal to 180°, while in the prototype the direction to the source is determined by the maximum amplitude and phase change. In addition, instead of a set of N hydrophones (at least 8 in the prototype) who is you can use almost one spot combo receiver including vector receiver and hydrophone.

The method of determining bearing on noisy underwater or surface of the object, including the measurement at one point of the acoustic field at the same time the four physical quantities: three orthogonal components of the vector of oscillatory speedand the acoustic pressure p(t) using combined receiver, including vector receiver and hydrophone, converting the received signal into a digital code, place it in an analytical form, the calculation of the ratio of the imaginary part of the signal to the actual to obtain the tangent of the phase and jump on the phase difference between the acoustic pressure p(t) and orthogonal components of oscillatory velocity V_x(t, α) and V_y(t, α) when electric rotating around the z-axis of the directivity vector of the receiver determine the bearing to the noisy object.