CN114353934B - Improved method for restoring free sound field from complex sound field - Google Patents
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Abstract
The invention relates to an improved method for restoring a free sound field from a complex sound field, which belongs to the technical field of free field restoration and comprises the following steps: based on the measured sound pressure and normal vibration velocity on the measuring surface S, the outwards-transmitted sound pressure on the measuring surface S is obtained, the inwards-transmitted sound pressure on the sound source surface is obtained, an inwards-transmitted particle normal vibration velocity equation on the sound source surface is brought, the inwards-transmitted particle normal vibration velocity value on the sound source surface is obtained, the inwards-transmitted sound pressure value and the particle normal vibration velocity value on the sound source surface are substituted into an improved equation of a scattering sound pressure source on the sound source surface, the scattering sound pressure source on the sound source surface is obtained, and therefore the free radiation sound field of a steady-state sound source with a closed appearance in a complex sound field environment is restored. The effectiveness of the improved sound field restoration method is verified in a numerical experiment mode, and the influence caused by failure frequency can be overcome.
Description
Technical Field
The invention belongs to the technical field of free field restoration, and relates to an improved method for restoring a free sound field from a complex sound field.
Background
The vibration sound radiation problem of structure exists in fields such as vehicle engineering, aerospace, ship engineering and ocean engineering extensively, like: noise is significant to concealment of underwater submarines and strategic significance of vitality, and on-board noise affects living comfort of crews and the like. Therefore, the importance of the problem of vibration acoustic radiation is increasingly gaining attention. Restoring the sound field of a vibrating structure sound source is an effective means of analyzing the problem of vibrating sound radiation of the structure.
In recent decades, the technology of the method for restoring the sound field of the sound source is developed rapidly, but the method has respective limitations and disadvantages. Such as: although the near field holographic technology can characterize a source through non-contact measurement, the noisy working environment cannot meet the requirements of free field conditions; the relevant scholars then propose near field holographic techniques based on the field separation technique (SFST) to reconstruct the free field of the target source radiation, but in most cases scattering the sound field is very important in noisy bounded environments, especially at high frequencies. Although related methods have been available for free sound field restoration in complex sound field environments, there is still the problem of sound field restoration failure due to inaccurate diffuse sound field calculations at certain frequencies. Thus, there is an urgent need for an improved method for solving the problem of failure at certain frequencies when recovering a freely radiating sound field from a complex sound field.
Disclosure of Invention
In order to solve the problems, the invention provides the following technical scheme: an improved method of restoring a free sound field from a complex sound field, comprising the steps of:
based on the measured sound pressure and normal vibration velocity on the measurement surface S, the outwardly propagating sound pressure on the measurement surface S is obtained,
based on the sound pressure and the normal vibration velocity on the measurement surface S, the inwardly propagating sound pressure at the sound source surface is obtained,
substituting the normal velocity equation of the inwardly-propagating particles at the sound source surface based on the sound pressure and the normal velocity at the measurement surface S to obtain the normal velocity value of the inwardly-propagating particles at the sound source surface,
substituting the inwardly-propagating sound pressure value and the particle normal vibration velocity value at the sound source surface into an improved equation of the scattered sound pressure source on the sound source surface to obtain the scattered sound pressure source on the sound source surface,
acquiring a scattering sound field on a measurement surface S based on the scattering sound pressure source;
and eliminating the scattered sound field from the outwards-transmitted sound field on the measuring surface S, and restoring the free radiation sound field of the steady sound source with the closed appearance in the complex sound field environment.
Further, the inward propagating particle normal velocity equation at the sound source surface is:
wherein: r is the field point and r' is the source point.
k=ω/c is the wave number, ω is the angular frequency, ρ is the density of the medium, and c is the speed of sound in the medium. />
Is the normal derivative at point r'. />
Is the normal derivative at point r.
Further, the improvement equation of the scattered sound pressure source on the sound source surface is:
wherein: Γ -shaped structure 1 Is the sound source surface, p B (r') is Γ 1 A source of scattered sound pressure at point r', coupling coefficient alpha = -i/k,
k=ω/c is the wave number, ω is the angular frequency, ρ is the density of the medium, and c is the speed of sound in the medium.
Compared with the prior art, the invention has the following advantages:
the invention adopts an improved method for restoring the free sound field from the complex sound field, achieves the aim of overcoming the restoration failure of the sound field under certain frequencies, verifies the effectiveness of the method by adopting a numerical experiment mode by applying the algorithm, and can solve the problem of the restoration failure of the sound field under certain frequencies.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to the drawings without inventive effort to a person skilled in the art.
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a schematic diagram of sound source, interference source and measurement plane of a complex sound field environment according to an embodiment of the present invention;
FIG. 3 is a graph of acoustic power level error versus signal-to-noise ratio at different frequencies in an embodiment of the present invention;
fig. 4 is a sound pressure level error plot of the restored sound field at kr=3.07 in an embodiment of the present invention;
fig. 5 is a sound pressure level error plot of the restored sound field at kr=3.16 in an embodiment of the present invention;
fig. 6 is a sound pressure level error plot of the restored sound field at kr=3.23 in an embodiment of the present invention;
FIG. 7 is a graph of signal-to-noise ratios at different measurement points on a measurement surface in an embodiment of the present invention.
Detailed Description
It should be noted that, without conflict, the embodiments of the present invention and features in the embodiments may be combined with each other, and the present invention will be described in detail below with reference to the drawings and the embodiments.
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
The relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. Meanwhile, it should be clear that the dimensions of the respective parts shown in the drawings are not drawn in actual scale for convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.
In the description of the present invention, it should be understood that the azimuth or positional relationships indicated by the azimuth terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal", and "top, bottom", etc., are generally based on the azimuth or positional relationships shown in the drawings, merely to facilitate description of the present invention and simplify the description, and these azimuth terms do not indicate and imply that the apparatus or elements referred to must have a specific azimuth or be constructed and operated in a specific azimuth, and thus should not be construed as limiting the scope of protection of the present invention: the orientation word "inner and outer" refers to inner and outer relative to the contour of the respective component itself.
Spatially relative terms, such as "above … …," "above … …," "upper surface at … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial location relative to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "over" other devices or structures would then be oriented "below" or "beneath" the other devices or structures. Thus, the exemplary term "above … …" may include both orientations of "above … …" and "below … …". The device may also be positioned in other different ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
In addition, the terms "first", "second", etc. are used to define the components, and are only for convenience of distinguishing the corresponding components, and the terms have no special meaning unless otherwise stated, and therefore should not be construed as limiting the scope of the present invention.
FIG. 1 is a flow chart of the present method; an improved method of restoring a free sound field from a complex sound field, comprising the steps of:
s1: based on the measured sound pressure and normal vibration velocity on the measurement surface S, the outwardly propagating sound pressure value on the measurement surface S is obtained,
s2: based on the sound pressure and the normal vibration velocity on the measurement surface S, an inwardly propagating sound pressure value at the sound source surface is obtained,
s3: substituting the normal velocity equation of the inwardly-propagating particles at the sound source surface based on the sound pressure and the normal velocity at the measurement surface S to obtain the normal velocity value of the inwardly-propagating particles at the sound source surface,
s4: substituting the sound pressure value and the normal vibration velocity of the particle at the sound source surface into an improved equation of the scattered sound pressure source on the sound source surface to obtain the scattered sound pressure source on the sound source surface,
s5: acquiring a scattering sound field on a measurement surface S based on the scattering sound pressure source;
s6: and eliminating the scattered sound field from the outwards-transmitted sound field on the measuring surface S, and restoring the free radiation sound field of the steady sound source with the closed appearance in the complex sound field environment.
S1, S2, S3, S4, S5 and S6 are sequentially carried out in sequence; s2, S1, S3, S4, S5, S6 may be performed sequentially;
further, based on the measured sound pressure and normal vibration velocity on the measurement surface S, the sound pressure value propagated outwards on the measurement surface S is obtained, which comprises the following specific procedures:
based on the measured sound pressure and normal vibration velocity on the measurement surface S, the outwardly propagating sound pressure value, p, on the measurement surface S is obtained o (r) can be determined by the following formula:
where r is the field point and r' is the source point.
k=ω/c is the wave number, ω is the angular frequency, and c is the speed of sound in the medium. />
Is the normal derivative at point r', ρ is the density of the medium, and the same applies below.
Based on the sound pressure and normal vibration velocity on the measurement surface S, the normal vibration velocity value of the inwardly-propagating particles at the sound source surface is obtained,
can be determined by the following formula:
based on the sound pressure and normal vibration velocity on the measurement surface S, the sound pressure value of inward propagation at the sound source surface is obtained, p i (r) can be determined by the following formula:
wherein: the function ψ (r, r '; ω) is the free space green's function base solution:
wherein: r= |r-R '|, R is the field point, R' is the source point.
k=ω/c is the wave number, ω is the angular frequency, and c is the speed of sound in the medium.
Further, parameters such as the sound pressure value and the particle normal velocity of inward propagation at the sound source surface are substituted into an improvement equation of the scattered sound pressure source on the sound source surface, so that the scattered sound pressure source on the sound source surface is obtained:
wherein: Γ -shaped structure 1 Is the sound source surface, p B (r') is Γ 1 A scattering sound pressure source at the point r', coupling coefficient α= -i/k.
Finally, acquiring a diffuse sound field p on the measurement surface S based on the diffuse sound pressure source s The formula (r) is as follows:
restoring by rejecting the diffuse sound field from the outwardly propagating sound field on the measuring surface SFree radiating acoustic field for a sound source with a closed profile in a complex acoustic field environment
Wherein p is o (r) is the outwardly propagating sound pressure value, p, on the measurement surface S s (r) is the diffuse sound field on the measurement surface S.
The scheme and the method of the invention are verified and further described below by specific application examples.
In this embodiment, in order to demonstrate the effectiveness of the improved method for recovering the free radiation sound field from the complex sound field, which has a failure problem at some frequency, a numerical example was designed, as shown in fig. 2, in which a pulsating sphere with a radius of 1.0m is used as a target source, a cubic space with a length of 10.0m is used as a closed sound cavity, the cubic space is a rigid boundary, and the measuring surface S is a sphere with a radius of 1.05 m. The center of the target source, the room and the measurement surface are all located at the origin of the coordinates, and as shown in fig. 2, another pulsating sphere with a radius of 0.25m is introduced as an interference source, with the center located at the coordinates (2.5 m ). Medium density ρ=1.2 kg/m 3 Medium sound speed c=340 m/s. Pulsating ball and disturbing sound source normal vibration velocity v=1m/s.
FIG. 3 is a graph of acoustic power level error and signal-to-noise ratio at different frequencies for evaluation of free field pressure for recovery by the algorithm presented in this invention, in accordance with an embodiment of the present invention. The following are used to determine the error of the sound power level and the signal-to-noise ratio SNR of the target source, respectively:
in (W) analytical ) i And (W) f ) i The resolved acoustic power and the recovered free field acoustic power at the i-th measurement cell on the target source, respectively. N represents the total number of measuring points on the measuring surface. (P) f ) i 、(P i ) i And (P) s ) i Respectively the free radiation pressure, the incident sound pressure and the scattering pressure of the ith cell on the measuring surface S i Represents the area of the i-th cell on the measurement surface S, || 2 Is the square of the modulus.
As can be seen from fig. 3, the condition number can ensure that matrix morbidity is avoided. At kr=3.07, the acoustic power level error of the original method and the improved sound field restoration method of the present invention is still greater than-21.0 dB. This suggests that too low a signal-to-noise ratio results in significant errors in the original method and the improved sound field restoration method of the present invention. In addition, as can be seen from fig. 3, the improved sound field restoration method of the present invention achieves better results when kr=3.16, while the error of the original method is significant when the condition number is large. The improved sound field restoration method can obtain a good restoration effect compared with the original method on the premise of ensuring reasonable signal-to-noise ratio.
Fig. 4 is a sound pressure level error plot of the restored sound field at kr=3.07 in an embodiment of the present invention;
fig. 5 is a sound pressure level error plot of the restored sound field at kr=3.16 in an embodiment of the present invention;
fig. 6 is a sound pressure level error plot of the restored sound field at kr=3.23 in an embodiment of the present invention;
FIG. 7 is a graph of signal-to-noise ratios at different measurement points on a measurement surface in an embodiment of the present invention.
The results of figures 4, 5, 6 and 7 show the sound pressure level errors at all points of the measurement surface and the signal to noise ratios at different frequencies at all points; the error of the sound power level and the signal to noise ratio of the measuring point on the measuring surface S are calculated as follows:
errors＝20log 10(|P f |/|P analytical |) (10)
SNR＝20log 10(|P f |/|P i +P s |) (11)
wherein: p (P) analytical And P f The free field resolved radiation sound pressure and the recovered free field sound pressure of the respective measuring points on the measuring surface S, respectively. P (P) f 、P i And P s The free field radiation sound pressure, the incident sound pressure, and the scattered sound pressure of the respective measurement points on the measurement surface S are represented, respectively, || is the magnitude of the mode.
As can be seen from fig. 4, 5, 6 and 7, there are significant errors in both the original method and the improved sound field restoration method of the present invention due to the low signal-to-noise ratio; the improved sound field restoration method of the invention avoids the problem of excessive condition number of coefficient matrix under the proper signal-to-noise ratio, and overcomes the problem of failure frequency, while the original method still has the problem of failure frequency under the proper signal-to-noise ratio; under the conditions of proper signal-to-noise ratio and lower condition number, the original method and the improved sound field restoration method of the invention both obtain better free field restoration effect. This suggests that too low a signal-to-noise ratio results in a large free field recovery error. Even if the signal-to-noise ratio is negative, the improved sound field restoration method can solve the problem of failure frequency and accurately restore the free field pressure.
In the embodiments provided in the present application, it should be understood that the disclosed technology may be implemented in other manners. The above-described embodiments of the apparatus are merely exemplary, and the division of the units, for example, may be a logic function division, and may be implemented in another manner, for example, a plurality of units or components may be combined or may be integrated into another system, or some features may be omitted, or not performed.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (1)
1. An improved method for restoring a free sound field from a complex sound field, comprising the steps of:
based on the measured sound pressure and normal vibration velocity on the measurement surface S, the outwardly propagating sound pressure on the measurement surface S is obtained,
based on the sound pressure and the normal vibration velocity on the measurement surface S, the inwardly propagating sound pressure at the sound source surface is obtained,
substituting the normal velocity equation of the inwardly-propagating particles at the sound source surface based on the sound pressure and the normal velocity at the measurement surface S to obtain the normal velocity value of the inwardly-propagating particles at the sound source surface,
the normal velocity equation of an inwardly propagating particle at the sound source surface is:
wherein: r is the field point, r' is the source point,
k=ω/c is the wave number, ω is the angular frequency, ρ is the density of the medium, c is the speed of sound in the medium, +.>
Is the normal derivative at point r'; />
Is the normal derivative at point r;
substituting the inwardly-propagating sound pressure value and the particle normal vibration velocity value at the sound source surface into an improved equation of the scattered sound pressure source on the sound source surface to obtain the scattered sound pressure source on the sound source surface,
the improvement equation of the scattered sound pressure source on the sound source surface is as follows:
wherein: Γ -shaped structure 1 Is the sound source surface, p B (r') is Γ 1 A source of scattered sound pressure at point r', coupling coefficient alpha = -i/k,
k=ω/c is the wave number, ω is the angular frequency, ρ is the density of the medium, c is the speed of sound in the medium,
acquiring a scattering sound field on a measurement surface S based on the scattering sound pressure source;
and eliminating the scattered sound field from the outwards-transmitted sound field on the measuring surface S, and restoring the free radiation sound field of the steady sound source with the closed appearance in the complex sound field environment.
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| JP2007263691A (en) * | 2006-03-28 | 2007-10-11 | Isuzu Motors Ltd | Sound pressure estimation method |
| JP2008064639A (en) * | 2006-09-08 | 2008-03-21 | Ono Sokki Co Ltd | Radiation power arithmetic device, sound pressure arithmetic device, particle velocity arithmetic device, radiation power arithmetic program, sound pressure arithmetic program, and particle velocity arithmetic program |
| CN101566496A (en) * | 2009-06-05 | 2009-10-28 | 合肥工业大学 | Method for sound field separation by double plane vibration speed measurement and equivalent source method |
| CN110487393A (en) * | 2019-08-19 | 2019-11-22 | 安徽大学 | The unstable state free field restoring method measured using single side acoustic pressure and particle velocity |
| CN113063490A (en) * | 2021-03-12 | 2021-07-02 | 北京科技大学 | Sound field separation method based on sound pressure and particle vibration velocity double-sided measurement |
| CN113432703A (en) * | 2021-06-04 | 2021-09-24 | 大连海事大学 | Method for restoring free radiation sound field of steady-state sound source with any shape |
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Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007263691A (en) * | 2006-03-28 | 2007-10-11 | Isuzu Motors Ltd | Sound pressure estimation method |
| JP2008064639A (en) * | 2006-09-08 | 2008-03-21 | Ono Sokki Co Ltd | Radiation power arithmetic device, sound pressure arithmetic device, particle velocity arithmetic device, radiation power arithmetic program, sound pressure arithmetic program, and particle velocity arithmetic program |
| CN101566496A (en) * | 2009-06-05 | 2009-10-28 | 合肥工业大学 | Method for sound field separation by double plane vibration speed measurement and equivalent source method |
| CN110487393A (en) * | 2019-08-19 | 2019-11-22 | 安徽大学 | The unstable state free field restoring method measured using single side acoustic pressure and particle velocity |
| CN113063490A (en) * | 2021-03-12 | 2021-07-02 | 北京科技大学 | Sound field separation method based on sound pressure and particle vibration velocity double-sided measurement |
| CN113432703A (en) * | 2021-06-04 | 2021-09-24 | 大连海事大学 | Method for restoring free radiation sound field of steady-state sound source with any shape |
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