CN101387547B - Diffuse sound prediction method - Google Patents

Abstract

The invention discloses a method for predicting diffuse sound. The method comprises the following steps: distributing a microphone array on discrete points on the surface of a scatter for measuring sound pressure p(ri) on the position of the discrete points; setting a Green function G(re|ri) from each microphone position on the surface of the scatter to predicting points in the space, wherein G(re| ri) is equal to ejk|r3-[e<-ri|]/(4pi|re-ri|);and substituting the measured result and the set Green function value into the formula that ps(re) is approximately equal to -sigma p(ri)(/n)G(re|ri)Si to obtain diffuse sound pressure, wherein Si is the area represented by each discrete point on the surface of the scatter. The microphone array is evenly distributed on the surface of the scatter, or distributed on the vertex of an irregular polyhedron taking the surface of the scatter as an externally-connected curved surface. Compared with the prior method, the method for predicting the diffuse sound has the advantages of accurate prediction and simple calculation.

Description

Diffuse sound prediction method

One, technical field

The present invention relates to a kind of diffuse sound prediction method.

Two, background technology

Diffuse sound control militarily has important application, can make immersed body such as submarine avoid the monitoring of detection system.Traditional method is at scatterer surface lay acoustic absorbant, yet it is not good in the low-frequency range noise reduction.The active control technology of diffuse sound can act on low-frequency range, but has difficulties in application: what error pick-up measured in the actual active guidance system is total sound field information, and calculate the optimum control source required be scattered field information.Existent method can be distinguished incident sound and reflected sound under one-dimensional condition; For the three-dimensional scattering body, French scientist (E.Friot, C.Bordier, " Real-time active suppression of scattered acoustic radiation; " J.SoundVib.Volume 278,563-580) propose, can distinguish diffuse sound, but need complicated measurement in early stage to determine filter parameter by filtering to total sound field.

Prior art also fail to provide a kind of prediction accurately, calculate simple three-dimensional scattering sound prediction method, be used for actual diffuse sound active guidance system.

Three, summary of the invention

The purpose of this invention is to provide a kind of prediction accurately, calculate simple three-dimensional scattering sound prediction method.And microphone array to lay the position feasible in actual applications.This method by measuring discrete point place, scatterer surface acoustic pressure and set the Green function of scatterer surface discrete point future position to the space, solved the problem of from total sound field, distinguishing diffuse sound.

A) the present invention is achieved through the following technical solutions: lay microphone array on the discrete point on scatterer surface, be used to measure the acoustic pressure of its position

B) Green function of each microphone position of setting scatterer surface future position to the space $G\left({\stackrel{\&RightArrow;}{r}}_e\right|{\stackrel{\&RightArrow;}{r}}_i)=-e^{-\mathrm{jk}|{\stackrel{\&OverBar;}{r}}_e-{\stackrel{\&RightArrow;}{r}}_i|}/\left(4\mathrm{\&pi;}\right|{\stackrel{\&RightArrow;}{r}}_e-\left|{\stackrel{\&RightArrow;}{r}}_i\right).$

With A) measurement result and B) the following formula of setting value substitution, can get the scattering pressure in the space: $p_s\left({\stackrel{\&RightArrow;}{r}}_e\right)\&ap;-\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}p\left({\stackrel{\&RightArrow;}{r}}_i\right)\frac{\&PartialD;}{\&PartialD;\stackrel{\&OverBar;}{n}}G\left({\stackrel{\&RightArrow;}{r}}_e\right|{\stackrel{\&RightArrow;}{r}}_i)S_i$

S wherein _iArea for each discrete point representative on the scatterer surface.

The even cloth of microphone array is put in the scatterer surface, and promptly for spherical scatterer, microphone array is put in cloth with on the regular polygon summit of scatterer surface as circumscribed circle; Have the scatterer of definite shape and volume for other, microphone array is put in cloth with on the irregular polyhedrons summit of scatterer surface as external curved surface.

Evenly lay four microphones on spherical scatterer surface, under the prediction spherical coordinate system

The diffuse sound of point; Evenly lay eight microphones on spherical scatterer surface, under the prediction spherical coordinate system

The diffuse sound of point.Wherein, true origin is spherical scatterer center.

The invention has the beneficial effects as follows: the present invention realizes than more accurate, the simpler Forecasting Methodology of existing Forecasting Methodology by setting the Green function of scatterer surface discrete point future position to the sound field.The position that lays of microphone array is feasible in actual applications among the present invention.

Four, description of drawings

Fig. 1 is an array structure synoptic diagram of the present invention;

Fig. 2 is a theory diagram of the present invention;

Fig. 3 is that the scatterer surface evenly lays four microphones, under the prediction spherical coordinate system (Fig. 3 a) and phase error (Fig. 3 b) for range error during the diffuse sound of point.

Fig. 4 is that the scatterer surface evenly lays eight microphones, under the prediction spherical coordinate system

(Fig. 4 a) and phase error (Fig. 4 b) for range error during the diffuse sound of point.

Five, embodiment

The present invention is described in detail below by example: as shown in Figure 1, the diffuse sound forecasting techniques of present embodiment comprises that even cloth is placed on the microphone array on scatterer surface: for spherical scatterer, microphone array cloth is placed on on the regular polygon summit of scatterer surface as circumscribed circle; Have the scatterer of definite shape and volume for other, microphone array is put in cloth with on the irregular polyhedrons summit of scatterer surface as external curved surface.As shown in Figure 2, the present invention includes two parts: the setting of the measurement module of scatterer surface discrete point place acoustic pressure, the scatterer surface discrete point Green function of future position to the space.

By the total acoustic pressure of any point in the sound field

Expression formula

$p\left({\stackrel{\&RightArrow;}{r}}_e\right)={\&Integral;}_V{Q}_{\mathrm{vol}}\left({\stackrel{\&RightArrow;}{r}}_0\right)G\left({\stackrel{\&RightArrow;}{r}}_e\right|{\stackrel{\&RightArrow;}{r}}_0)\mathrm{dV}+{\&Integral;}_S[G\left({\stackrel{\&RightArrow;}{r}}_e\right|{\stackrel{\&RightArrow;}{r}}_0)\frac{\&PartialD;}{\&PartialD;\stackrel{\&RightArrow;}{n}}p\left({\stackrel{\&RightArrow;}{r}}_0\right)-p\left({\stackrel{\&RightArrow;}{r}}_0\right)\frac{\&PartialD;}{\&PartialD;\stackrel{\&RightArrow;}{n}}G\left({\stackrel{\&RightArrow;}{r}}_e\right|{\stackrel{\&RightArrow;}{r}}_0)]\mathrm{dS}---\left(1\right)$

And incident sound expression formula

$p_i\left({\stackrel{\&RightArrow;}{r}}_e\right)={\&Integral;}_V{Q}_{\mathrm{vol}}\left({\stackrel{\&RightArrow;}{r}}_0\right)G\left({\stackrel{\&RightArrow;}{r}}_e\right|{\stackrel{\&RightArrow;}{r}}_0)\mathrm{dV}---\left(2\right)$

Can get the diffuse sound expression formula

$p_s\left({\stackrel{\&RightArrow;}{r}}_e\right)={\&Integral;}_S[G\left({\stackrel{\&RightArrow;}{r}}_e\right|{\stackrel{\&RightArrow;}{r}}_0)\frac{\&PartialD;}{\&PartialD;\stackrel{\&RightArrow;}{n}}p\left({\stackrel{\&RightArrow;}{r}}_0\right)-p\left({\stackrel{\&RightArrow;}{r}}_0\right)\frac{\&PartialD;}{\&PartialD;\stackrel{\&RightArrow;}{n}}G\left({\stackrel{\&RightArrow;}{r}}_e\right|{\stackrel{\&RightArrow;}{r}}_0)]\mathrm{dS}---\left(3\right)$

p _iAnd p _sRepresent incident sound pressure and scattering pressure,

Be strength of sound source,

For primary source on the S of scatterer surface

Total acoustic pressure of point,

For from

Point arrives The Green function of point.For the rigidity scatterer, its surperficial acoustic pressure gradient is 0, and then the scattering pressure in the space can be expressed as

$p_s\left({\stackrel{\&OverBar;}{r}}_e\right)=-{\&Integral;}_{S}p\left({\stackrel{\&RightArrow;}{r}}_0\right)\frac{\&PartialD;}{\&PartialD;\stackrel{\&RightArrow;}{n}}G\left({\stackrel{\&RightArrow;}{r}}_e\right|{\stackrel{\&RightArrow;}{r}}_0)\mathrm{dS}---\left(4\right)$

Can get after discrete

$p_s\left({\stackrel{\&RightArrow;}{r}}_e\right)\&ap;-\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}p\left({\stackrel{\&RightArrow;}{r}}_i\right)\frac{\&PartialD;}{\&PartialD;\stackrel{\&RightArrow;}{n}}G\left({\stackrel{\&RightArrow;}{r}}_e\right|{\stackrel{\&RightArrow;}{r}}_i)S_i---\left(5\right)$

In (5) formula, The microphone array that is put in the scatterer surface by cloth measures; Discrete point Green function of future position to the space in scatterer surface is set at

For spherical scatterer, when the even cloth of microphone array is placed on the scatterer surface, S _i=4 π a ²/ N, wherein a is the scatterer radius.

Be that the spherical scatterer surface of 0.18m evenly lays 4 microphones at radius in the present embodiment, predict under the spherical coordinate system

Diffuse sound; Evenly lay 8 microphones on this scatterer surface, predict under the spherical coordinate system

Diffuse sound.Wherein, true origin is spherical scatterer center.Fig. 3 and Fig. 4 shown in certain range error and falling phase error, the acoustic pressure by measuring discrete point place, scatterer surface and set scatterer surface discrete point Green function of future position to the sound field and can effectively predict diffuse sound in the space.

Claims (2)

1. diffuse sound prediction method: it is characterized in that on the discrete point on scatterer surface, laying microphone array, be used to measure the acoustic pressure of its position

The Green function of each microphone position of setting scatterer surface future position to the space

$G\left({\stackrel{\&RightArrow;}{r}}_e\right|{\stackrel{\&RightArrow;}{r}}_i)=e^{-\mathrm{jk}|{\stackrel{\&RightArrow;}{r}}_e-{\stackrel{\&RightArrow;}{r}}_i|}/\left(4\mathrm{\&pi;}\right|{\stackrel{\&RightArrow;}{r}}_e-{\stackrel{\&RightArrow;}{r}}_i\left|\right);$

With the result of measurement and the following formula of Green function value substitution of setting, get the scattering pressure in the space:

$p_s\left({\stackrel{\&RightArrow;}{r}}_e\right)\&ap;-\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}p\left({\stackrel{\&RightArrow;}{r}}_i\right)\frac{\&PartialD;}{\&PartialD;\stackrel{\&RightArrow;}{n}}G\left({\stackrel{\&RightArrow;}{r}}_e\right|{\stackrel{\&RightArrow;}{r}}_i)S_i,$ S wherein _iArea for each discrete point representative on the scatterer surface;

The even cloth of microphone array is put in the scatterer surface, and promptly for spherical scatterer, microphone array is put in cloth with on the regular polygon summit of scatterer surface as circumscribed circle; Have the scatterer of definite shape and volume for other, microphone array is put in cloth with on the irregular polyhedrons summit of scatterer surface as external curved surface.

2. diffuse sound prediction method according to claim 1: it is characterized in that evenly laying four microphones, under the prediction spherical coordinate system on spherical scatterer surface

The diffuse sound of point; Evenly lay eight microphones on spherical scatterer surface, under the prediction spherical coordinate system

The diffuse sound of point.

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