A noise reduction method based on forced acoustic component analysis

Abstract

The application particularly relates to a noise reduction method based on forced sound-vibration component analysis, which comprises the following steps: obtaining a transfer function between a normal vibration velocity of a structure surface and a radiated sound pressure according to an experiment or a numerical method, and constructing a vibration-sound transfer function matrix; performing singular value decomposition on the vibration-sound transfer function matrix, thereby obtaining forced sound-vibration components, and analyzing and comparing contribution amounts of the components to the structure radiated sound pressure; formulating a targeted noise reduction scheme according to the contribution amount size, and realizing reduction of the structure noise. The application can reveal main vibration components generating sound radiation, and then a noise reduction scheme is proposed according to the forced sound-vibration component contribution value size. The above method is also applicable to sound power, and after a transfer function matrix between sound power and the normal vibration velocity of the structure surface is obtained, forced sound-vibration component analysis is adopted for noise reduction.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of vibration and noise reduction, and particularly relates to a noise reduction method based on forced sound-vibration component analysis. BACKGROUND

[0002] Currently, the main way of vibration and noise reduction is to suppress structural vibration to achieve the purpose of noise reduction. This method believes that sound is caused by vibration, and noise reduction can be achieved by suppressing structural vibration. However, this noise reduction idea is one-sided, although sound is caused by vibration, not all vibrations can effectively produce sound (here, effective sound production refers to sound radiated to the far field).

[0003] In actual engineering applications, modal analysis method is often used to suppress vibration and noise. This method is feasible for vibration reduction. Modal analysis reflects the relationship between structural excitation and vibration response, but does not establish the relationship between vibration response and sound radiation. Therefore, using modal analysis method to suppress sound radiation cannot obtain the most economical and effective noise reduction scheme. Therefore, it is necessary to study the relationship between vibration response and sound radiation, and to suppress the vibration component that effectively produces sound to achieve noise reduction. The contribution of different forced sound-vibration components is obtained by singular value decomposition of the sound-vibration transfer function matrix, and then the main sound-producing forced sound-vibration components are processed for noise reduction. This method can significantly improve the efficiency of noise reduction and save the cost of noise reduction.

[0004] Currently, the research on vibration and noise reduction mainly focuses on the analysis of noise sources. For example, Chinese invention patent application No. 202010747020.0, entitled "Substation noise reduction scheme based on sound source contribution analysis", proposes a method of determining the contribution function by noise source intensity and position, and then determining the treatment measures according to the contribution value of each sound source. For example, Chinese invention patent application No. 201811081485.6, entitled "Pipeline noise reduction method considering cross-sectional sound energy distribution", analyzes the frequency spectrum and modal information of incident sound waves, arranges sound-absorbing materials on the inner wall of the pipeline, and continuously optimizes the noise reduction scheme to obtain the final scheme. For example, Chinese invention patent application No. 202010103634.5, entitled "Water injection pump house noise control method", uses grid point method to test the noise inside the water injection pump house, determines the corresponding excessive amount, and designs a noise reduction scheme. SUMMARY

[0005] The technical problem to be solved by the present application is the technical problem involved in the background art. The present application provides a noise reduction method based on forced sound-vibration component analysis. The method of the present application can improve the efficiency of noise reduction and save the cost of noise reduction.

[0006] The noise reduction method based on forced sound-vibration component analysis of the present application comprises the following steps:

[0007] Step 1: obtain the transfer function between structural vibration and acoustic radiation according to experiment or numerical method, so as to obtain the vibration-sound transfer function matrix;

[0008] Step 2: singular value decomposition is performed on the above transfer function matrix, and the singular values are sorted in descending order, so as to obtain the vibration component with larger contribution to structural acoustic radiation;

[0009] Step 3: the vibration component with larger contribution is suppressed, and a targeted noise reduction scheme is formulated to achieve noise reduction.

[0010] The beneficial effect is that singular value decomposition of the vibration-sound transfer function can distinguish the forced vibration component for effective sound emission, and when noise reduction is performed, the amplitude of the entire system vibration does not need to be suppressed, but only the position of the forced vibration component for effective sound emission needs to be suppressed.

[0011] Further, the transfer function between the normal vibration velocity of the structure surface and the radiated sound pressure in step 1 is further explained, and is calculated by the following formula:

[0012]

[0013] The above formula is the sound pressure equation. Wherein ω represents the angular frequency of the excitation source, x represents the position of the field point, subscript S represents the number of field points, represents the radiated sound pressure vector, represents the normal vibration velocity vector of the structure surface. represents the transfer function matrix between the normal vibration velocity of the structure surface and the radiated sound pressure, which can be obtained by experiment or numerical method.

[0014] Further, the sound radiation parameter in step 1 can also be sound power, and the sound power equation is further explained, and is calculated by the following formula:

[0015]

[0016] Wherein represents the transfer function matrix between the normal vibration velocity of the structure surface and the sound power, which represents the sound power radiation efficiency of the noise source surface to the surrounding fluid medium. Not all structural vibration components can effectively emit sound, in order to achieve the purpose of vibration reduction and noise reduction, only the vibration component for effective sound emission needs to be suppressed, therefore the transfer function representing the noise sound power radiation efficiency is further studied.

[0017] Further, the singular value decomposition of the transfer function in step 2 is further explained, and the transfer function or is singular value decomposed. The transfer function matrix involved in the sound power equation Take the following example to illustrate. Performing singular value decomposition, the sound power equation can be obtained as:

[0018]

[0019] Among them, the singular value decomposition obtains the left unitary matrix [U] S×S , right unitary matrix [V] S×S and the diagonal matrix [Σ] S×S This step uses the singular value decomposition method to link the structural vibration and sound power radiation for further exploration.

[0020] Furthermore, the vibration components with the largest contribution to the structural vibration obtained in step 2 are further explained: the right unitary matrix [V] S×S Each column represents a component of the entire structural vibration, and the corresponding diagonal matrix [Σ] S×S The form is as follows:

[0021]

[0022] Among them, σ1>σ2>…>σ S , the singular value σ in the matrix S Indicates the sound radiation intensity of this component.

[0023] If the acoustic radiation parameter of interest is the radiation sound pressure at the field point, the transfer function matrix in the sound pressure equation needs to be Perform singular value decomposition and then suppress the radiated sound pressure based on the singular value sorting. The principle is similar to the above-mentioned suppression of sound power.

[0024] This method breaks down the distribution of structural vibration across the entire source surface into multiple mutually orthogonal components. Since structural vibration is a forced response to a specific excitation, and this forced response is frequency-dependent, resulting in acoustic radiation, these orthogonal components are referred to as forced acoustic components. Singular values ​​correspond one-to-one to forced acoustic components. Singular values ​​are ranked, with larger singular values ​​indicating a greater contribution of forced acoustic components to the structural vibration sound.

[0025] Furthermore, in step 3, a noise reduction scheme is formulated based on the contribution amount to further explain: according to the singular value sorting result, the forced acoustic vibration component with large contribution amount is subjected to noise reduction to replace the overall noise reduction method. Its beneficial effect is that according to the singular value σ s The size can distinguish the forced acoustic vibration components of effective sound. When performing noise reduction, there is no need to suppress the amplitude of the entire system vibration, but only to suppress the position of the forced vibration components of effective sound. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a noise reduction flow chart of the present invention;

[0027] Figure 2 Fig. 1 is a schematic diagram of singular value decomposition of noise transfer function according to the present application. DETAILED DESCRIPTION

[0028] The present application will now be further described in detail with reference to the accompanying drawings.

[0029] Referring to Figure 1 , the present application firstly establishes a transfer function according to the normal surface velocity obtained from structural vibration and the radiated sound pressure, and substitutes it into the sound power equation; the transfer function in the sound power equation is analyzed by using the singular value decomposition method to obtain the vibration component with greater contribution to the structural vibration; a noise reduction scheme is formulated according to the contribution amount, and noise reduction is performed, and the result meets the evaluation standard of noise reduction, thus completing the vibration and noise reduction.

[0030] Specifically, the relationship between the radiated sound pressure and the normal vibration velocity is obtained by using experimental test method or numerical calculation method:

[0031]

[0032] The above formula is the sound pressure equation. Wherein ω represents the angular frequency of the excitation source, x represents the field point position, subscript S represents the number of field points, represents the radiated sound pressure vector, represents the normal vibration velocity vector of the structure surface. represents the transfer function matrix between the normal vibration velocity of the structure surface and the radiated sound pressure, which can be obtained by experiment or numerical method.

[0033] The sound power radiated by the structure can be obtained by the following formula:

[0034]

[0035] Wherein ΔS represents the numerical discrete unit area of the sound source surface, ρ0 is the fluid medium density, c represents the propagation speed of sound in the fluid, Re represents the real part, and the superscript H represents Hermitian transformation.

[0036] Since the normal vibration velocity decays rapidly with distance, the sound power can be converted to the following formula:

[0037]

[0038] Further, according to the sound pressure equation, the above formula can be converted to:

[0039]

[0040] Wherein

[0041]

[0042] represents the transfer function matrix between the normal velocity of the structure surface and the sound power, and represents the sound power radiation efficiency of the noise source surface to the surrounding fluid medium. Not all structure vibration components can effectively radiate sound, and in order to achieve the purpose of vibration and noise reduction, only the vibration components that effectively radiate sound need to be suppressed, so the transfer function representing the sound power radiation efficiency is further studied.

[0043] The noise reduction method proposed by the present application is described below with the suppression of sound power as the target, and the suppression principle of radiated sound pressure is similar.

[0044] Referring to Figure 2 , the transfer function matrix is singular value decomposed, and the sound power is:

[0045]

[0046] Among them, the singular value decomposition obtains the left unitary matrix [U] S×S , the right unitary matrix [V] S×S and the diagonal matrix [Σ] S×S . This step uses the singular value decomposition method to associate the structure vibration and the sound power radiation, and further explores.

[0047] Furthermore, according to the size of the singular value, the time-averaged sound power contribution values of different forced sound vibration components are calculated and compared, and the noise components with large contribution values are processed for noise reduction. The right unitary matrix [V] S×S Each column represents a component of the entire structure vibration, and the corresponding diagonal matrix [Σ] S×S is as follows:

[0048]

[0049] Among them, σ1> σ2> … > σ S , the singular value σ S in the matrix represents the sound radiation intensity of the component.

[0050] If the concerned sound radiation parameter is the field point radiated sound pressure, the transfer function matrix in the sound pressure equation needs to be singular value decomposed, and then the singular value is sorted to suppress the radiated sound pressure. The principle is similar to the suppression of sound power described above.

[0051] In the embodiment of the present application, the structural vibration distribution on the whole surface of the vibration source is attributed to a plurality of mutually orthogonal components. Since the structural vibration is a forced response of a specific excitation, the forced response is related to frequency, thus leading to sound radiation, so these orthogonal components are called forced sound vibration components. The singular values and the forced sound vibration components belong to a one-to-one correspondence. The singular values are sorted, and the larger the singular value is, the greater the contribution of the forced sound vibration component to the sound emission of the structure is.

[0052] Then, according to the sorting result, the forced sound vibration component with large contribution is subjected to noise reduction processing to replace the overall noise reduction method. The beneficial effect is that, according to the singular value σ s The size can distinguish the forced sound vibration component that effectively emits sound, and when noise reduction is performed, the amplitude of the vibration of the whole system does not need to be suppressed, but only the position of the forced sound vibration component that effectively emits sound needs to be suppressed.

[0053] Finally, the sound power level (or sound pressure level) of the structure after noise reduction is compared with the sound power level (or sound pressure level) before noise reduction, and if the sound power level (or sound pressure level) is reduced, the noise reduction is successful.

[0054] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it. Although the present application has been described in detail with reference to the above embodiments, the ordinary skilled in the art can still modify or equivalently replace the specific embodiments of the present application, and any modification or equivalent replacement that does not deviate from the spirit and scope of the present application is within the protection scope of the claims of the present application.

Claims

1. A noise reduction method based on forced acoustic vibration component analysis, characterized in that: The following steps are involved: Step 1: Obtain the sound pressure equation and sound power equation between structural vibration and sound radiation based on experimental or numerical methods, thereby obtaining the vibration-acoustic transfer function matrix; Among them, the sound power equation can be expressed as: Where ΔS represents the sound source surface in the numerical discretization, ρ0 is the density of the fluid medium, c represents the propagation speed of sound in the fluid, Re represents the real part, and H represents the conjugate transpose. The transfer function representing the sound power equation, namely the vibration-acoustic transfer function matrix, represents the sound power radiation efficiency of the noise source surface to the surrounding fluid medium; Step 2: Perform singular value decomposition on the above vibration-acoustic transfer function matrix and sort the singular values ​​from large to small to obtain the vibration components that contribute most to the structural sound radiation; Among them, the singular value decomposition method is used to analyze the vibration-acoustic transfer function matrix After analysis, the sound power is obtained as: According to formula (2), the vibration-acoustic transfer function matrix After performing singular value decomposition, we can get the left unitary matrix [U] S×S , right unitary matrix [V] S×S and the diagonal matrix [∑] S×S , The vibration component that contributes most to the structure-borne sound radiation is specifically: the right unitary matrix [V] S×S Each column represents a component of the entire structure vibration, and the corresponding diagonal matrix [∑] S×S The form is as follows: Among them, σ1>σ2>L>σ s , the singular value σ in the matrix s It represents the sound radiation intensity of this component. The structural vibration distribution on the entire vibration source surface is reduced to multiple mutually orthogonal components. These orthogonal components are called forced acoustic vibration components. The singular values ​​are in a one-to-one correspondence with the forced acoustic vibration components. The singular values ​​are sorted from large to small. The larger the singular value, the greater the contribution of the forced acoustic vibration component to the structure-borne sound radiation. Step 3: Suppress the vibration components with larger contributions and develop a targeted noise reduction plan to achieve noise reduction.

2. The noise reduction method based on forced acoustic component analysis according to claim 1, characterized in that: The relationship between the normal velocity on the structure surface and the radiated sound pressure in step 1 can be described by the following formula: The above formula is the sound pressure equation, where ω represents the angular frequency of the excitation source, x represents the position of the field point, and the subscript S represents the number of field points. represents the radiated sound pressure vector, represents the normal velocity vector of the structure surface, The transfer function matrix between the normal vibration velocity of the structure surface and the radiated sound pressure is obtained through experiments or numerical methods.

3. The noise reduction method based on forced acoustic component analysis according to claim 1, characterized in that: In step 3, the noise reduction method is formulated according to the contribution size as follows: based on the singular value sorting results, the contribution ratio of the forced acoustic vibration component corresponding to each singular value can be determined. When the contribution ratio of the forced acoustic vibration component is high, the forced acoustic vibration component corresponding to the corresponding singular value is selected as the component that needs to be optimized for noise reduction. Based on the selected forced acoustic vibration component, the specific location of the effective sound source can be determined, and targeted noise reduction measures can be implemented. In the noise reduction process, the method of local noise reduction at the effective sound source location is used to replace the current common noise reduction method of suppressing the vibration of the entire noise source.

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