Constant-beamwidth beam forming method and system based on loudspeaker array

Abstract

The invention discloses a constant beamwidth beam forming method and system based on a loudspeaker array, and the method comprises the steps: determining the number and frequency range of loudspeakers used in the loudspeaker array according to the main lobe width which needs to be set for a beam; a constraint is added at each of a plurality of positions of the beam, the plurality of positions comprise a zero point position and a half-power bandwidth position, and each constraint corresponds to an adjustment parameter; and obtaining weight coefficients of all loudspeakers in the loudspeaker array according to the adjustment parameters. According to the invention, the zero point constraint and the half-power bandwidth constraint are additionally added, so that the main lobe width of the beam pattern radiated by the array can be kept consistent in a broadband range.

Description

Technical Field

[0001] The present invention relates to the technical field of constant beamwidth beamforming, and in particular to a constant beamwidth beamforming method and system based on a loudspeaker array. Background Art

[0002] A speaker array is an array-type sound system that uses speakers or transducers as array elements and arranges them in a certain geometric structure. By combining different geometric formations, the electrical signals applied to the speaker array are processed, including the amplitude, phase, frequency and other electrical characteristic quantities, to obtain different spatial sound field distributions. In many scenes in people's daily lives, speaker arrays are needed to control specific sound fields, and speaker arrays do face some challenges in sound field control.

[0003] Loudspeaker arrays with constant beamwidth are widely used in many places, such as airports, stations, conference rooms, classrooms, etc. Therefore, it is of great practical significance to study the constant beamwidth beamforming technology of loudspeaker arrays. Most of the loudspeaker arrays currently used are loudspeaker line arrays, which have many deficiencies in constant beamwidth beamforming capabilities. The traditional beamforming method is delay and summation. Since the traditional delay and sum (DAS) method is related to frequency, the main lobe beam of the beam pattern becomes narrower as the frequency increases, affecting the uniformity of the sound field. This phenomenon may lead to large differences in sound propagation effects at different frequencies, which in turn affects the audience's ability to obtain a uniform listening experience.

[0004] Therefore, it is necessary to provide a new type of constant beamwidth beamforming solution so that the width of the main lobe beam of the formed beam pattern can be kept consistent within a certain frequency range. Summary of the invention

[0005] The object of the present invention is to provide a constant beamwidth beamforming method and system based on a loudspeaker array, in which the main lobe width can be kept consistent over a wide frequency range.

[0006] To achieve the above object, on the one hand, the present invention proposes a constant beamwidth beamforming method based on a speaker array, comprising:

[0007] S1, determining the number and frequency range of loudspeakers used in the loudspeaker array according to the main lobe width required to be set for the beam, wherein the loudspeakers used include a first loudspeaker and a second loudspeaker;

[0008] S2, adding a constraint at each of the multiple positions of the beam, the multiple positions including a zero point position and a half-power bandwidth position, each of the constraints corresponding to an adjustment parameter;

[0009] S3: Obtain weight coefficients of all the speakers in the speaker array according to the adjustment parameters.

[0010] In a preferred embodiment, the S1 comprises:

[0011] S11, determining, according to the main lobe width, a maximum number of speakers and a minimum number of speakers of the speakers used so as to satisfy a constant main lobe width, and obtaining the frequency range according to the maximum number of speakers and the minimum number of speakers;

[0012] S12, obtaining the number of speakers used corresponding to different frequencies according to the frequency range and the main lobe width.

[0013] In a preferred embodiment, in S11, the frequency range is f L ~f H , where f L =c / (Lδsin(θ CBW / 2)), f H =c / (3δsin(θ CBW / 2)), where c represents the speed of sound waves in the air, L represents the maximum number of loudspeakers, L<the number of all loudspeakers in the loudspeaker array, δ represents the loudspeaker array spacing, θ CBW represents the main lobe width and 3 is the minimum number of speakers.

[0014] In a preferred embodiment, the S12 includes:

[0015] S121, calculating the number of the first speakers according to the frequency range and the main lobe width;

[0016] S122: Obtain the number of the second speakers according to the number of the first speakers and the added number of constraints, thereby obtaining the number of speakers used.

[0017] In a preferred embodiment, in S121, according to the formula (2K+1)f≤Lf L , the number of the first speakers is calculated, where (2K+1) is the number of the first speakers, K is a natural number greater than or equal to 1, f is a different frequency, and f L ≤f≤f H .

[0018] In a preferred embodiment, in S2, the corresponding adjustment parameter is calculated based on the beam value at the zero point position and the beam value at the half-power bandwidth position.

[0019] In a preferred embodiment, the beam value at the zero position is expressed as:

[0020]

[0021] The beam value at the half-power bandwidth position is expressed as:

[0022]

[0023] in, 2K+1 is the number of the first loudspeakers, K is a natural number greater than or equal to 1, f is the frequency, δ represents the array spacing, θ -3dB =0.886×θ null / 2,θ null =θ CBW / 2 ,θ -3dB Indicates the angle of -3dB on the right side, θ null Represents the angle of the right zero point, θ CBW represents the main lobe width, c represents the speed of the sound wave in the air, g1 and g2 are the adjustment parameters corresponding to the two constraints, and

[0024] According to the B(f, θ null ) and the B(f, θ -3dB ) values, and calculate the adjustment parameters g1, g2.

[0025] In a preferred embodiment, the S3 further includes:

[0026] The adjustment parameters are normalized to obtain weight coefficients of all speakers in the speaker array.

[0027] In a preferred embodiment, the weight coefficients of all the speakers are expressed as:

[0028]

[0029] On the other hand, the present invention proposes a constant beamwidth beamforming system based on a speaker array, comprising:

[0030] An array determination module, used to determine the number and frequency range of speakers used in the speaker array according to the main lobe width required to be set for the beam, wherein the speakers used include a first speaker and a second speaker;

[0031] An adjustment parameter determination module, used to add a constraint at each of multiple positions of the beam, wherein the multiple positions include a zero point position and a half-power bandwidth position, and each constraint corresponds to an adjustment parameter;

[0032] The weight coefficient determination module is used to obtain the weight coefficients of all the speakers in the speaker array according to the adjustment parameters.

[0033] Compared with the prior art, the present invention has the following beneficial effects: the present invention achieves the goal of keeping the main lobe width of array radiation unchanged by additionally adding zero point constraints and half-power bandwidth constraints. Compared with the traditional DAS method, the main lobe width of the beam pattern formed by the present invention can be kept consistent over a wide frequency range. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the process of the present invention;

[0035] Figure 2 A schematic diagram of a model of a loudspeaker array in a specific embodiment of the present invention;

[0036] Figure 3a and Figure 3b Schematic diagrams showing comparison of broadband two-dimensional sound field patterns of the conventional DAS method and the method of the present invention;

[0037] Figure 4a and Figure 4b They are schematic diagrams comparing beam patterns of the conventional DAS method and the method of the present invention in the frequency range of 1000 Hz to 6000 Hz;

[0038] Figure 5 It is a schematic block diagram of the system of the present invention. DETAILED DESCRIPTION

[0039] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0040] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0041] like Figure 1 As shown, the present invention discloses a constant beamwidth beamforming method based on a speaker array, comprising the following steps:

[0042] S1. Determine the number and frequency range of loudspeakers used in a loudspeaker array according to a main lobe width required to be set for a beam, wherein the loudspeakers used include a first loudspeaker and a second loudspeaker.

[0043] Specifically, the main lobe width of the beam is related to the product of the number of speakers used in the speaker array and the frequency. In order to maintain a constant main lobe width, the product of the number of speakers used and the frequency should remain unchanged, so the number of speakers can be determined according to the change of frequency. During implementation, the main lobe width is set as required, and it is best to cover the directivity range required by the speaker array.

[0044] During implementation, the S11 specifically includes the following steps:

[0045] S11, determining the maximum number of speakers and the minimum number of speakers used to satisfy the requirement of a constant main lobe width according to the main lobe width, and obtaining the frequency range according to the maximum number of speakers and the minimum number of speakers.

[0046] Specifically, in a specific embodiment, if the main lobe width is assumed to be θ CBW The speaker array is a linear speaker array. The number of speakers is 21. The speakers are evenly spaced. The array spacing δ is 5 cm. The speakers are symmetrically arranged on both sides of the coordinate origin (on the left and right sides of the origin, respectively). Because the number of speakers in the speaker array is set to an odd number greater than 1, the minimum number of speakers is set to 3, and the maximum number of speakers is defined as L. L is an odd number greater than 3, L = 2 × L0 + 1, and L0 is Figure 2 The number of speakers on one side. After the maximum and minimum number of speakers are determined, the corresponding minimum and maximum frequencies are also determined. Specifically, the minimum frequency is defined as f L , which is the frequency corresponding to the maximum number of loudspeakers, f L =c / (Lδsin(θ CBW / 2)); On the contrary, the maximum frequency is defined as f H , which is the frequency corresponding to the minimum number of loudspeakers, f H =c / (3δsin(θ CBW / 2)), where c represents the speed of sound waves in air, L represents the maximum number of loudspeakers, L is less than the number of all loudspeakers in the loudspeaker array, δ represents the loudspeaker array spacing, θ CBW Represents the main lobe width.

[0047] The minimum frequency and maximum frequency can be used to determine the frequency range of the loudspeaker array, that is, the frequency range is f L ~f H .

[0048] S12, obtaining the number of speakers used corresponding to different frequencies according to the frequency range and the main lobe width.

[0049] Specifically, during implementation, the S12 specifically includes the following steps:

[0050] S121: Calculate the number of the first speakers according to the frequency range and the main lobe width.

[0051] The first loudspeaker here refers to the basic loudspeaker that can achieve the main lobe width. When implemented, it can be implemented according to the formula (2K+1)f≤Lf L , the number of the first speakers is calculated, where (2K+1) is the number of the first speakers, K is a natural number greater than or equal to 1, f is a different frequency, and f L ≤f≤f H That is, the formula can be used to determine the number of first loudspeakers corresponding to each frequency within the above frequency range.

[0052] S122: Obtain the number of the second speakers according to the number of the first speakers and the added number of constraints, thereby obtaining the number of speakers used.

[0053] Specifically, in this embodiment, since two constraints are added and the speaker array is symmetrical about the origin, two speakers need to be added for each additional constraint, so in this embodiment, the number of second speakers is 4. The number of speakers used is the sum of the number of first speakers and second speakers, that is, in this embodiment, the number of speakers used is 2K+5. Of course, in other alternative embodiments, the added constraints are not limited to the two here, such as 3, and the corresponding number of second speakers added can be 6.

[0054] S2, adding a constraint at each of the multiple positions of the beam, the multiple positions including a zero point position and a half-power bandwidth position, each of the constraints corresponding to an adjustment parameter.

[0055] Specifically, in order to optimize the smoothness of the beam and ensure a certain main wave width, in this embodiment, it is preferred to add a constraint at the zero point position and the half-power bandwidth position of the beam, wherein the beam value at the zero point position is expressed as:

[0056]

[0057] The beam value at the half-power bandwidth position is expressed as:

[0058]

[0059] in, 2N+1 is the number of the first loudspeakers, K is a natural number greater than or equal to 1, f is the frequency, δ represents the array spacing, θ -3dB =0.886×θ null / 2,θ null =θ CBW / 2 ,θ -3dB Indicates the angle of -3dB on the right side, θ null Represents the angle of the right zero point, θ CBWrepresents the main lobe width, c represents the speed of the sound wave in the air, g1 and g2 are the adjustment parameters corresponding to the two constraints, and

[0060] Since the beam values ​​at the null position and the half-power bandwidth position are known, So from this B(f,θ null ) and B(f,θ -3dB ), the two adjustment parameters g1 and g2 corresponding to the two constraints can be calculated, that is, the beam is controlled by the two adjustment parameters.

[0061] S3: Obtain weight coefficients of all the speakers in the speaker array according to the adjustment parameters.

[0062] Because the beam pattern is obtained by the product of the weight vector and the moment of inertia, the effect of constant beam width is mainly achieved by designing different weight vectors. Preferably, in this embodiment, in order to make the maximum beam value B equal to 1 and facilitate comparison with other methods, the present invention also normalizes the adjustment parameters g1 and g2 to obtain the weights of all speakers in the speaker array. Specifically expressed as:

[0063]

[0064] Corresponding to the above method, Figure 5 As shown, the present invention discloses a constant beamwidth beamforming system based on a speaker array, comprising:

[0065] The array determination module is used to determine the number and frequency range of loudspeakers used in the loudspeaker array according to the main lobe width required to be set for the beam, wherein the loudspeakers used include a first loudspeaker and a second loudspeaker.

[0066] The adjustment parameter determination module is used to add a constraint at multiple positions of the beam respectively, the multiple positions include a zero point position and a half-power bandwidth position, and each constraint corresponds to an adjustment parameter.

[0067] The weight coefficient determination module is used to obtain the weight coefficients of all the speakers in the speaker array according to the adjustment parameters.

[0068] The implementation principles of the array determination module, the adjustment parameter determination module and the weight coefficient determination module may refer to the descriptions in the above steps S1, S2 and S3 respectively, and will not be elaborated here.

[0069] The following is a simulation comparison of the method proposed by the present invention and the traditional DAS method with a specific example. Figure 2 As shown, a speaker array with 21 speakers is selected, the array spacing is 5 cm, and the main lobe width is set to 40°. Figure 3a and 3b As shown in FIG. 1 , a two-dimensional acoustic field diagram simulation is performed to compare the method of the present invention with the DAS method. From the figure, it can be seen that as the frequency increases, the main lobe width of the DAS (delayed sum) method becomes narrower, while the main lobe width of the method of the present invention remains basically the same. Figure 4a and Figure 4b In the embodiment, the beam patterns of the DAS method and the method of the present invention are further simulated in a wideband range of 1000 Hz to 6000 Hz. It can be found that the main lobe of the present invention remains basically the same, while the main lobe width of the DAS method becomes narrower as the frequency increases.

[0070] The advantage of the present invention is that the present invention achieves the goal of keeping the array radiation main lobe width unchanged by additionally adding zero point constraints and half-power bandwidth constraints. Compared with the traditional DAS method, the main lobe width of the beam pattern formed by the present invention can remain consistent over a wide frequency range.

[0071] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A constant beamwidth beamforming method based on a loudspeaker array, characterized in that: The method comprises: S1, determining the number and frequency range of loudspeakers used in the loudspeaker array according to the main lobe width required to be set for the beam, wherein the loudspeakers used include a first loudspeaker and a second loudspeaker; S2, adding a constraint at each of the multiple positions of the beam, the multiple positions including a zero point position and a half-power bandwidth position, each of the constraints corresponding to an adjustment parameter; S3: Obtain weight coefficients of all the speakers in the speaker array according to the adjustment parameters.

2. A constant beamwidth beamforming method based on a speaker array as claimed in claim 1, characterized in that: The S1 includes: S11, determining, according to the main lobe width, a maximum number of speakers and a minimum number of speakers of the speakers used so as to satisfy a constant main lobe width, and obtaining the frequency range according to the maximum number of speakers and the minimum number of speakers; S12, obtaining the number of speakers used corresponding to different frequencies according to the frequency range and the main lobe width.

3. A constant beamwidth beamforming method based on a speaker array as claimed in claim 2, characterized in that: In S11, the frequency range is f L ~f H , where f L =c / (Lδsin(θ CBW / 2)), f H =c / (3δsin(θ CBW / 2)), where c represents the speed of sound waves in the air, L represents the maximum number of loudspeakers, L<the number of all loudspeakers in the loudspeaker array, δ represents the loudspeaker array spacing, θ CBW represents the main lobe width and 3 is the minimum number of speakers.

4. The constant beamwidth beamforming method based on a speaker array according to claim 3, characterized in that: The S12 includes: S121, calculating the number of the first speakers according to the frequency range and the main lobe width; S122: Obtain the number of the second speakers according to the number of the first speakers and the added number of constraints, thereby obtaining the number of speakers used.

5. A constant beamwidth beamforming method based on a speaker array as claimed in claim 4, characterized in that: In S121, according to the formula (2K+1)f≤Lf L , the number of the first speakers is calculated, where (2K+1) is the number of the first speakers, K is a natural number greater than or equal to 1, f is a different frequency, and f L ≤f≤f H .

6. The method for constant beamwidth beamforming based on a loudspeaker array according to claim 1, characterized in that: In S2, the corresponding adjustment parameter is calculated according to the beam value at the zero point position and the beam value at the half-power bandwidth position.

7. A constant beamwidth beamforming method based on a speaker array as claimed in claim 6, characterized in that: The beam value at the zero position is expressed as: The beam value at the half-power bandwidth position is expressed as: Wherein, 2K+1 is the number of the first loudspeakers, K is a natural number greater than or equal to 1, f is the frequency, δ represents the array spacing, θ -3dB =0.886×θ null / 2,θ null =θ CBW / 2 ,θ -3dB Indicates the angle of -3dB on the right side, θ null Represents the angle of the right zero point, θ CBW represents the main lobe width, c represents the speed of the sound wave in the air, g1 and g2 are the adjustment parameters corresponding to the two constraints, and B(f, θ null )=0, According to the B(f, θ null ) and the B(f, θ -3dB ) values, and calculate the adjustment parameters g1, g2.

8. The constant beamwidth beamforming method based on a speaker array according to claim 7, characterized in that: The S3 further includes: The adjustment parameters are normalized to obtain weight coefficients of all speakers in the speaker array.

9. A constant beamwidth beamforming method based on a speaker array as claimed in claim 8, characterized in that: The weight coefficients of all the speakers are expressed as:

10. A constant beamwidth beamforming system based on a speaker array, characterized in that: The system comprises: An array determination module, used to determine the number and frequency range of speakers used in the speaker array according to the main lobe width required to be set for the beam, wherein the speakers used include a first speaker and a second speaker; An adjustment parameter determination module, used to add a constraint at each of multiple positions of the beam, wherein the multiple positions include a zero point position and a half-power bandwidth position, and each constraint corresponds to an adjustment parameter; The weight coefficient determination module is used to obtain the weight coefficients of all the speakers in the speaker array according to the adjustment parameters.

Images