CN113432703A - Method for restoring free radiation sound field of steady-state sound source with any shape - Google Patents
Method for restoring free radiation sound field of steady-state sound source with any shape Download PDFInfo
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Abstract
The invention provides a method for restoring a free radiation sound field of a steady-state sound source with any shape, which comprises the following steps: collecting sound pressure signals on two layers of holographic measuring surfaces from a complex sound field, determining a sound pressure signal and a particle normal vibration velocity on a middle holographic measuring surface, and acquiring a sound pressure signal of an inward propagation sound field on the surface of a sound source and an outward propagation sound field on the middle holographic measuring surface based on the sound pressure signal and the particle normal vibration velocity on the middle holographic measuring surface; acquiring a scattering sound pressure double-layer potential source on the surface of a sound source based on an inward propagation sound field at the surface of the sound source; acquiring a scattering sound field on the intermediate holographic measuring surface based on the scattering sound pressure double-layer potential source; and eliminating the scattered sound field from the outward propagation sound field on the intermediate holographic measuring surface, and restoring a free radiation sound field of a steady sound source with any (closed/non-closed) shape in a complex sound field environment.
Description
Technical Field
The invention relates to the technical field of free field recovery, in particular to a method for restoring a free radiation sound field of a steady sound source with any (closed/non-closed) shape from a complex sound field.
Background
The vibration sound radiation problem of the structure is widely existed in the fields of vehicle engineering, aerospace, ship engineering, ocean engineering and the like, such as: the noise has great strategic significance on the concealment and the vitality of the underwater submarine, and the noise on the ship influences the living comfort of crews and the like. Therefore, the importance of the problem of vibration sound radiation is increasingly gaining attention. Restoring the sound field of a vibrating structure sound source is an effective means for analyzing the problem of vibration sound radiation of the structure.
In recent decades, the method for restoring the sound field of the sound source has been developed rapidly, but has its limitations and disadvantages. Such as: although the near-field holographic technology can represent a source through non-contact measurement, the noisy working environment cannot meet the requirements of free field conditions; the relevant authors subsequently proposed that near-field holography based on the field-splitting technique (SFST) was done to reconstruct the free field of the target source radiation, but in most cases, in noisy, bounded environments, the scattered sound field is very important, especially at high frequencies. It is not sufficient to use the acoustic field separation based technique alone to take the output pressure as the free field pressure because the scattered field cannot be eliminated from the output pressure field; in order to solve this problem, researchers have proposed free sound field restoration techniques based on the direct boundary element method and the equivalent source method, but the above methods can only restore the sound field of a closed-profile steady-state sound source. Therefore, there is an urgent need for a method for recovering a free-radiated sound field from a complex sound field with a stable sound source having an arbitrary (closed/non-closed) shape.
Disclosure of Invention
According to the technical problem that a steady-state sound source free radiation sound field with any shape cannot be restored from a complex sound field, the method for restoring the steady-state sound source free radiation sound field with any (closed/non-closed) shape from the complex sound field is provided. The invention analyzes and processes sound Field sound pressure signals and particle vibration velocity signals on a holographic measuring surface based on an FFR (Free Field Recovery) algorithm of an indirect BEM (Boundary Element Method), and realizes the Recovery of a Free radiation sound Field of a steady-state sound source with any (closed/non-closed) shape.
The technical means adopted by the invention are as follows:
a method of restoring a steady state sound source free-radiating sound field having an arbitrary shape from a complex sound field, comprising:
collecting sound pressure signals on two layers of holographic measuring surfaces from a complex sound field, determining a sound pressure signal and a particle normal vibration velocity on a middle holographic measuring surface, and acquiring a sound pressure signal of an inward propagation sound field on the surface of a sound source and an outward propagation sound field on the middle holographic measuring surface based on the sound pressure signal and the particle normal vibration velocity on the middle holographic measuring surface;
acquiring a scattering sound pressure double-layer potential source on the surface of a sound source based on an inward propagation sound field at the surface of the sound source;
acquiring a scattering sound field on a holographic measuring surface based on the scattering sound pressure double-layer potential source;
and eliminating the scattered sound field from the outward propagation sound field on the intermediate holographic measuring surface, and restoring a free radiation sound field of a steady sound source with any shape in a complex sound field environment.
Further, acquiring the sound pressure signals of the inward propagation sound field on the sound source surface and the outward propagation sound field on the intermediate holographic measurement surface based on the sound pressure signal on the intermediate holographic measurement surface and the particle normal vibration velocity, includes:
and inputting the sound pressure signal as a signal to be processed and the normal vibration velocity of the mass point as the signal to be processed, inputting an internal and external field sound field separation equation, and further outputting the sound pressure signal of the inward propagation sound field on the surface of the sound source and the outward propagation sound field on the intermediate holographic measuring surface.
Further, acquiring a scattered sound pressure double-layer potential source on a sound source surface based on an inward propagating sound field at the sound source surface, comprising: and inputting a scattered sound pressure double-layer potential source calculation equation in an indirect boundary element form by taking the inward propagation sound field on the surface of the sound source obtained by separation as a signal to be processed, and outputting the scattered sound pressure double-layer potential source on the surface of the sound source.
Further, acquiring a scattering sound field on an intermediate holographic measurement surface based on the scattering sound pressure double-layer potential source, including: and inputting the scattering sound pressure double-layer potential source into a scattering sound field equation in an indirect boundary element form, and outputting a scattering sound field on the intermediate holographic measuring surface.
Compared with the prior art, the invention has the following advantages:
the invention provides an FFR algorithm based on indirect BEM, which analyzes, processes and collects sound field sound pressure signals and particle vibration velocity signals on a middle holographic measuring surface and can realize the reduction of a free radiation sound field of a steady sound source with any (closed/non-closed) shape in a complex sound field environment.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for restoring a free-radiation sound field of a steady-state sound source with an arbitrary (closed \ non-closed) shape from a complex sound field according to the present invention.
FIG. 2 is a schematic view of a measurement plane in an embodiment of the present invention.
Fig. 3 is a schematic diagram of a closed acoustic chamber with a target acoustic source and a noise source in an embodiment of the present invention.
Fig. 4 shows the acquired complex sound field sound pressure signal amplitude, the outward propagation sound field sound pressure signal amplitude, and the calculated sound source free radiation sound field sound pressure signal amplitude on the intermediate holographic measurement surface at the frequency of 200Hz in the embodiment of the present invention.
Fig. 5 shows the absolute error and the relative error of the calculated amplitude of the sound pressure signal of the sound source free radiation sound field and the restored amplitude of the sound pressure signal of the sound source free sound field.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
As shown in fig. 1, the present invention provides a method for restoring a free-radiation sound field of a steady-state sound source with an arbitrary (closed \ non-closed) shape from a complex sound field, comprising:
and S1, collecting sound pressure signals on the two layers of holographic measuring surfaces from the complex sound field, determining the sound pressure signals on the middle holographic measuring surface and the normal vibration velocity of the mass point, and acquiring the sound pressure signals of the inward propagation sound field on the sound source surface and the outward propagation sound field on the middle holographic measuring surface based on the sound pressure signals on the middle holographic measuring surface and the normal vibration velocity of the mass point. The method for determining the sound pressure signal and the particle vibration speed on the intermediate holographic measuring surface comprises the following steps:
in the formula, Vn(r) is the normal vibration speed of the mass point at r point on the middle holographic measuring surface,
ρ is the medium density, ω is the angular frequency of the acoustic signal, and d is the distance between the two holographic measurement surfaces.
Representing the sound pressure signal on the inner holographic measurement surface,
the measurement surface is shown in fig. 2 for the sound pressure signal on the outer holographic measurement surface.
Specifically, the sound pressure signal is input as a signal to be processed and the normal vibration velocity of the mass point is input as a signal to be processed, an internal and external field sound field separation equation is input, and then the sound pressure signal of the inward propagation sound field on the sound source surface and the outward propagation sound field on the intermediate holographic measurement surface are output. Complex sound field signals are collected on two layers of holographic measuring surfaces by using microphones, r is arranged on a middle holographic measuring surface, and then a sound field p which is outwards propagated on the middle holographic measuring surfaceo(r) may be determined using an outward propagation sound field separation equation:
placing r at the surface of the sound source, then the sound field p propagating inwards at the surface of the sound sourcei(r) may be determined using an in-propagating sound field separation equation:
in the formula, po(r) denotes the outward propagation of the acoustic field on the intermediate holographic surface, pi(r) represents an inwardly propagating sound field at the surface of the sound source;
is the particle normal vibration velocity signal on the middle holographic measuring surface, p (r ') is the sound pressure signal on the middle holographic measuring surface, S (r') represents the unit area on the middle holographic measuring surface,
and R is a green function, R is a spatial point on the intermediate holographic measurement plane or the sound source surface, R ' is a spatial point on the intermediate holographic measurement plane, and R-R ' represents the distance between R and R '.
Where k is the wave number, ρ is the medium density, ω is the angular frequency of the acoustic signal, c is the medium sound velocity,
is the normal derivative of psi (r, r'; omega).
And S2, acquiring a scattered sound pressure double-layer potential source on the surface of the sound source based on the inward propagation sound field at the surface of the sound source. Specifically, an inward propagation sound field on the surface of the sound source obtained through separation is used as a signal to be processed, a scattered sound pressure double-layer potential source calculation equation in an indirect boundary element form is input, and a scattered sound pressure double-layer potential source on the surface of the sound source is output.
The calculation equation of the double-layer potential source of the scattering sound pressure in the indirect boundary element form is as follows:
in the formula, δ pB(r') is a scattered sound pressure double-layer potential source on the sound source surface,
representing the normal gradient of the incident sound field particle at the surface of the sound source, can be determined using the normal derivative equation of the in-propagating sound field separation equation.
Wherein the content of the first and second substances,
is a green function
Second order normal derivatives with respect to r and r'.
And S3, acquiring a scattering sound field on the intermediate holographic measuring surface based on the scattering sound pressure double-layer potential source. Specifically, a scattering sound field equation in an indirect boundary element form is input into a scattering sound pressure double-layer potential source, and a scattering sound field on a holographic measurement surface is output.
The scattering sound field equation in the indirect boundary element form is as follows:
in the formula, psAnd (r) is a scattering sound field on the intermediate holographic measurement surface.
S4, removing the scattered sound field from the outward propagation sound field on the intermediate holographic measuring surface, and restoring a free radiation sound field of a steady sound source with any (closed/non-closed) shape in a complex sound field environment. Specifically, the free radiation sound field of a steady-state sound source with an arbitrary (closed \ non-closed) shape on the holographic surface can be calculated by the following formula:
in the formula (I), the compound is shown in the specification,
the free radiation acoustic field on the surface is measured for the intermediate hologram.
The scheme and effect of the present invention will be further described by specific application examples.
In this embodiment, the radius of the pulsating spherical sound source is 1m, the radius of the holographic measuring surface is 1.05m, the spherical radius of the interfering sound source is 0.1m, the normal vibration speed v of the pulsating spherical sound source and the interfering sound source is 1m/s, the closed sound cavity is a cube with a side length of 7.5 m, and the boundary thereof is a rigid boundary. The sound radiation frequency is 200Hz, and the medium density rho is 1.2kg/m3The medium sound velocity c is 340m/s, and an example analysis model is shown in FIG. 3.
The interference in a complex sound field is simulated by the interference ball with the same frequency as the pulsating ball and the closed sound cavity, and the free radiation sound field information of the pulsating ball sound source is restored by applying the FFR technical algorithm based on the indirect BEM provided by the embodiment. In the embodiment of the invention, under the frequency of 200Hz, the sound pressure signal amplitude of a complex sound field on two layers of holographic measuring surfaces is acquired, the sound pressure signal amplitude of an outward transmission sound field is acquired by separation, and the sound pressure signal amplitude of a free radiation sound field of a sound source is acquired by calculation, as shown in FIG. 4; and calculating the absolute error and the relative error of the amplitude of the sound pressure signal of the free radiation sound field of the sound source and the sound pressure signal of the free sound field of the sound source obtained by reduction, as shown in fig. 5. As can be seen from the figure, the amplitude difference is less than 26pa, and the error is less than 7.5% compared with the original sound source from the sound pressure of the sound field, which indicates that the algorithm can restore the steady-state sound source free radiation sound field with any (closed \ non-closed) shape from the complex sound field.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.
In the above embodiments of the present invention, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
In the embodiments provided in the present application, it should be understood that the disclosed technology can be implemented in other ways. The above-described embodiments of the apparatus are merely illustrative, and for example, the division of the units may be a logical division, and in actual implementation, there may be another division, for example, multiple units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, units or modules, and may be in an electrical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a removable hard disk, a magnetic or optical disk, and other various media capable of storing program codes.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (4)
1. A method for restoring a free-radiating sound field with an arbitrary shape from a stable sound source in a complex sound field, comprising:
collecting sound pressure signals on two layers of holographic measuring surfaces from a complex sound field, determining a sound pressure signal and a particle normal vibration velocity on a middle holographic measuring surface, and acquiring a sound pressure signal of an inward propagation sound field on the surface of a sound source and an outward propagation sound field on the middle holographic measuring surface based on the sound pressure signal and the particle normal vibration velocity on the middle holographic measuring surface;
acquiring a scattering sound pressure double-layer potential source on the surface of a sound source based on an inward propagation sound field at the surface of the sound source;
acquiring a scattering sound field on a holographic measuring surface based on the scattering sound pressure double-layer potential source;
and eliminating the scattered sound field from the outward propagation sound field on the intermediate holographic measuring surface, and restoring a free radiation sound field of a steady sound source with any shape in a complex sound field environment.
2. The method according to claim 1, wherein the obtaining of the sound pressure signals of the inward-propagating sound field at the sound source surface and the outward-propagating sound field at the intermediate holographic measurement surface based on the sound pressure signal at the intermediate holographic measurement surface and the particle normal vibration velocity comprises:
and inputting the sound pressure signal as a signal to be processed and the normal vibration velocity of the mass point as the signal to be processed, inputting an internal and external field sound field separation equation, and further outputting the sound pressure signal of the inward propagation sound field on the surface of the sound source and the outward propagation sound field on the intermediate holographic measuring surface.
3. The method of claim 1, wherein the method for recovering a steady-state sound source free-radiating sound field with an arbitrary (closed \ non-closed) shape from a complex sound field is characterized in that a scattered sound pressure double-layer potential source on a sound source surface is obtained based on an inward propagation sound field at the sound source surface, and comprises the following steps: and inputting a scattered sound pressure double-layer potential source calculation equation in an indirect boundary element form by taking the inward propagation sound field on the surface of the sound source obtained by separation as a signal to be processed, and outputting the scattered sound pressure double-layer potential source on the surface of the sound source.
4. The method for recovering a steady sound source free-radiation sound field with an arbitrary shape from a complex sound field according to claim 1, wherein the acquiring of the scattering sound field on the holographic measuring surface based on the scattering sound pressure double-layer potential source comprises: and inputting the scattering sound pressure double-layer potential source into a scattering sound field equation in an indirect boundary element form, and outputting a scattering sound field on the holographic measuring surface.
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