Sound amplification unit capable of controlling sound field range

Abstract

The invention provides a sound amplification unit capable of controlling a sound field range. The sound amplification unit comprises a sound gathering cover and a linear sound source sound column arranged in the sound gathering cover. The line sound source sound columns comprise medium-high frequency sound columns and low-frequency sound columns which are arranged back to back, and the low-frequency sound columns face the opening direction of the sound gathering cover. The cross section of the sound gathering cover is in the shape of a first-order parabola or a second-order combined parabola. The sound amplification unit forms a sound field control system, realizes effective control of the diffusion range of sound waves, and can effectively reduce sound pollution and sound interference caused by sound leakage and sound staining.

Description

Technical Field

[0001] The present invention relates to a sound amplification device, and in particular to a sound amplification unit with a controllable sound field range. This sound amplification unit includes a sound focusing cover and a line source sound column arranged inside the sound focusing cover, constituting a sound field control system to effectively control the diffusion range of sound waves, and can effectively reduce sound pollution and sound interference caused by sound leakage and sound coloring. Background Art

[0002] Theoretically, a point source is a spherical wave, and a line source is a cylindrical wave, and their transmission characteristics are essentially different. As Figure 1 shown, the wavefront generated by the point source 2 is a concentric sphere, which is called a spherical wave. Suppose there is a spherical sound source in an infinite homogeneous medium, whose surface expands and contracts rapidly, and each point on the surface vibrates with the same phase and amplitude, and the wave radiated to the surrounding medium is a spherical wave. This kind of sound wave is spherically symmetric, that is, the magnitude of the sound pressure is only related to the distance from the center of the sphere. Any sound source with a size much smaller than the wavelength can be regarded as a point source and radiates spherical waves. For a spherical wave, the sound intensity at any distance from the sound source is inversely proportional to the square of the distance, the sound pressure is inversely proportional to the distance, and the phase difference between the sound pressure and the vibration velocity is inversely proportional to the ratio of the radius of the spherical wave to the wavelength.

[0003] As Figure 2 shown, the wavefront generated by the line source 4 is a wave of coaxial cylinders, which is called a cylindrical wave. A cylindrical wave is a wave with a coaxial cylindrical wavefront. Suppose there is an infinitely long uniform line source in an infinite homogeneous medium, and the wave it generates is an ideal cylindrical sound wave. In a cylindrical sound wave, the amplitude of the sound pressure is uniformly distributed along the axial direction and is inversely proportional to the square root of the distance from the axis along the radial direction. Its radial sound intensity is inversely proportional to the first power of the distance from the axis.

[0004] It can be seen from the above acoustic theory analysis that the acoustic characteristics of the line source composed of cylindrical waves are far superior to those of the point source composed of traditional spherical waves. Specifically, it is manifested in: 1. Transmission characteristics, with twice the efficiency. 2. Good coupling characteristics and low distortion caused by interference. 3. Better directivity control (strong directivity characteristics in the vertical direction). Therefore, how to convert spherical waves into cylindrical waves has become the main research direction of researchers in this industry.

[0005] In the prior art, Chinese Patent Application, CN202210427881.X, discloses a sound amplification sound column with adjustable vertical directivity. This technology constitutes a line source sound column through a series of coaxial cylindrical wave medium and high frequency speakers.

[0006] In actual sound amplification applications, there are many occasions where the sound amplification range needs to be accurately controllable to reduce interference caused by mutual influence between sound sources. For example, the zoning sound control requirements in museums and exhibition halls, or in the case of square dance venues, sound pollution and disputes with residents often occur due to the uncontrollable sound field range. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a sound amplification unit with a controllable sound field range. This sound amplification unit combines a sound concentrating cover and a line source sound column arranged inside the sound concentrating cover to perform three-dimensional control on the sound wave diffusion and achieve precise control of the sound field range.

[0008] The present invention provides a sound amplification unit with a controllable sound field range, including a sound concentrating cover and a line source sound column arranged inside the sound concentrating cover.

[0009] As an improvement, the line source sound column includes a mid-high frequency sound column and a low frequency sound column arranged back to back, and the low frequency sound column faces the opening direction of the sound concentrating cover.

[0010] As an improvement, the cross-section of the sound concentrating cover presents a first-order parabola, the acoustic center point of the mid-high frequency sound column is at the focus of the first-order parabola, the opening width of the first-order parabola is equal to the wavelength corresponding to the mid-low frequency crossover frequency, the first-order parabola extends along the axis direction of the line source sound column to form a first-order paraboloid, and the first-order paraboloid forms the inner surface of the sound concentrating cover.

[0011] Furthermore, the cross-section of the sound concentrating cover presents a second-order combined parabola, the acoustic center point of the mid-high frequency sound column is at the focus of the first-order parabola, the opening width of the first-order parabola is equal to the wavelength corresponding to the mid-low frequency crossover frequency, the acoustic center of the low frequency sound column is at the focus of the second-order parabola, the opening width of the second-order parabola is equal to the wavelength corresponding to the lower limit of the controllable frequency of the low frequency sound column, the first-order parabola and the second-order parabola intersect at the intersection point, the second-order combined parabola is composed of the first-order parabola before the intersection point and the second-order parabola after the intersection point, the second-order combined parabola extends along the axis direction of the line source sound column to form a second-order combined paraboloid, and the second-order combined paraboloid forms the inner surface of the sound concentrating cover.

[0012] The beneficial effects brought by the present invention compared with the prior art are as follows: (1) By using the line source sound column, the control of sound wave diffusion along the axis direction of the line source sound column is realized. As the length of the sound column axis increases, the lower limit of the controllable frequency will decrease. (2) By using the sound focusing effect of the sound concentrating cover, the control of sound waves in the opening direction of the sound concentrating cover is realized. The diffusion control of mid-high frequency sound waves is achieved through the first-order paraboloid, and the diffusion control of low frequency sound waves is achieved through the second-order paraboloid. (3) By using the sound reflection effect of the sound concentrating cover, the diffusion control of sound waves in the axis direction of the second-order combined parabola is realized. Finally, it can be realized that the sound pressure difference between the inner and outer sound fields of the sound concentrating cover is ≥ 25 dB. Description of the Drawings

[0013] Figure 1 It is a schematic diagram of a point source and a spherical wave.

[0014] Figure 2 It is a schematic diagram of a line source and a cylindrical wave.

[0015] Figure 3A and Figure 3B is a schematic structural diagram of a line source sound column in an embodiment of the present invention.

[0016] Figure 4 is a schematic cross-sectional structure diagram of a sound amplification unit in an embodiment of the present invention.

[0017] Figure 5 is a sound pressure test curve of the internal and external sound fields of a sound focusing cover in an embodiment of the present invention. Detailed implementation manners

[0018] The present invention will be further described below with reference to the accompanying drawings of the specification.

[0019] As Figure 1 , as shown in the schematic diagram of a point source and spherical wave, the wavefront generated by the point source 2 is a concentric sphere, which is called a spherical wave. Suppose there is a spherical sound source in an infinite homogeneous medium, its surface expands and contracts rapidly, and each point on the surface vibrates with the same phase and amplitude, and the wave radiated to the surrounding medium is a spherical wave. This kind of sound wave is spherically symmetric, that is, the magnitude of the sound pressure is only related to the distance from the center of the sphere. Any shape of sound source, as long as its size is much smaller than the wavelength, can be regarded as a point source and radiate spherical waves. For spherical waves, the sound intensity at any distance from the sound source is inversely proportional to the square of the distance. As shown in the figure, when the distance from the sound source increases from R to R2, that is, twice of R, the area of the wavefront increases from A to 4A, and the sound intensity drops to 1 / 4.

[0020] As Figure 2 , as shown in the schematic diagram of a line source and cylindrical wave, the wavefront generated by the line source 4 is a wave of coaxial cylinders, which is called a cylindrical wave. A cylindrical wave is a wave whose wavefront is a coaxial cylinder. Suppose there is an infinitely long uniform line source in an infinite homogeneous medium, and the wave it generates is an ideal cylindrical sound wave. In a cylindrical sound wave, the sound pressure amplitude is uniformly distributed along the axial direction and is inversely proportional to the square root of the distance from the axis along the radial direction. Its radial sound intensity is inversely proportional to the first power of the distance from the axis. As shown in the figure, when the distance from the sound source increases from R to R2, that is, twice of R, the area of the wavefront increases from A to 2A, and the sound intensity drops to 1 / 2.

[0021] As Figure 3A and Figure 3B , as shown in the schematic structural diagram of a line source sound column, where Figure 3A is a side view, Figure 3BIt is the front view. In an embodiment of the present invention, a line source sound column 6 includes a mid-high frequency sound column 8 and a low frequency sound column 10 arranged back to back, and the low frequency sound column 10 faces the opening direction of the sound gathering cover (not shown). The mid-high frequency sound column 8 is composed of a row of 6 coaxial mid-high frequency horns 12, and the low frequency sound column 10 is composed of a row of 4 low frequency horns 14. The axis 16 of the mid-high frequency horn 12 is parallel to the axis 18 of the low frequency horn 14, and is in a plane with the axis 20 of the line source sound column 6, the mid-high frequency sound column 8, and the low frequency sound column 10.

[0022] Figure 4 It is a schematic cross-sectional structure diagram of the sound amplification unit in an embodiment of the present invention. This cross-section cuts across the axis in the length direction of the sound amplification unit 22, that is, the axis of the line source sound column. Therefore, a coaxial mid-high frequency horn 12 and a low frequency horn 14 are shown in the figure. The mid-high frequency horn 12 and the low frequency horn 14 are arranged back to back, and the low frequency horn 14 faces the opening direction of the sound gathering cover 24. The axis 16 of the mid-high frequency horn 12 is parallel to the axis 18 of the low frequency horn 14, so the axis 16 and the axis 18 are shown to be collinear in the cross-sectional view.

[0023] Figure 4 It also further shows the design scheme of the second-order combined parabolic surface on the inner surface of the sound gathering cover 24. In the cross-sectional view, the sound gathering cover 24 is in the shape of a thin shell, and the cross-section of the sound gathering cover 24 presents a second-order combined parabola. The acoustic center point F1 of the mid-high frequency sound column, that is, the mid-high frequency horn 12, is at the focus of the first-order parabola P1, and the opening width L1 of the first-order parabola P1 is equal to the wavelength corresponding to the mid-low frequency crossover frequency. The acoustic center F2 of the low frequency sound column, that is, the low frequency horn 14, is at the focus of the second-order parabola P2, and the opening width L2 of the second-order parabola P2 is equal to the wavelength corresponding to the lower limit of the controllable frequency of the low frequency sound column. The first-order parabola P1 and the second-order parabola P2 intersect at the intersection point C. The second-order combined parabola is composed of the first-order parabola P1 before the intersection point C (that is, the left side of the C point in the figure) and the second-order parabola P2 after the intersection point C (that is, the right side of the C point in the figure). The second-order combined parabola extends along the axis direction of the line source sound column to form a second-order combined parabolic surface, and the second-order combined parabolic surface forms the inner surface of the sound gathering cover.

[0024] Correspondingly, if the second-order parabola is not set, the cross-section of the sound gathering cover presents a first-order parabola. The acoustic center point of the mid-high frequency sound column is at the focus of the first-order parabola, and the opening width of the first-order parabola is equal to the wavelength corresponding to the mid-low frequency crossover frequency. The first-order parabola extends along the axis direction of the line source sound column to form a first-order parabolic surface, and the first-order parabolic surface forms the inner surface of the sound gathering cover.

[0025] The design steps of the sound amplification unit of the present invention mainly include:

[0026] (1) Determine the structure and external dimensions of the sound column. According to the requirements of sound amplification technical indicators under actual application conditions, select low, medium, and high-frequency horns, set the crossover frequency, and determine the external dimensions of the sound column and the frequency response range of the controllable sound field according to the specifications of the horns.

[0027] (2) Calculate the crossover point frequency. According to the line source theory, the acoustic center distance between two adjacent horns should be less than or equal to half of the wavelength corresponding to the coupling upper limit frequency. Considering that the acoustic center distance between two adjacent horns is approximately equal to the diameter of the horn, the crossover frequency can be determined according to the specifications of the selected horns. For example, the crossover point between low frequency and medium frequency can be calculated based on the diameter of the low-frequency horn, and the crossover point between medium frequency and high frequency can be calculated based on the diameter of the medium-frequency horn.

[0028] (3) Determine the acoustic centers of the medium and high-frequency horns and the low-frequency horn. Theoretically, the acoustic center of the horn is located at the center of the voice coil. The medium and high-frequency horn adopts a coaxial medium and high-frequency horn, and through electronic delay compensation, its coupled acoustic center is located at the center position between the centers of the medium-frequency horn and the high-frequency horn. The acoustic center of the low-frequency horn is located at the center of the voice coil of the low-frequency horn.

[0029] (4) Determine the second-order combined parabolic surface of the sound concentrating cover. According to acoustic theory, the size of the baffle is approximately equal to the wavelength of the controllable frequency. Therefore, it can be deduced that the opening width L1 of the first-order parabola is equal to the wavelength corresponding to the crossover frequency between low frequency and medium frequency. In addition, the acoustic center F1 of the medium and high-frequency horn is at the focus of the first-order parabola P1. Thus, the shape of the first-order parabola P1 corresponding to the medium and high-frequency horn can be determined. Similarly, the opening width L2 of the second-order parabola P2 is equal to the wavelength corresponding to the lower limit of the controllable frequency of the low-frequency sound column. Moreover, the acoustic center F2 of the low-frequency horn is at the focus of the second-order parabola P2. Thus, the shape of the second-order parabola P2 corresponding to the low-frequency horn can be determined. Then, the first-order parabola P1 and the second-order parabola P2 intersect at the intersection point C. The second-order combined parabola is composed of the first-order parabola P1 before the intersection point C (i.e., the left side of point C in the figure) and the second-order parabola P2 after the intersection point C (i.e., the right side of point C in the figure). The second-order combined parabola expands along the axis direction of the line source sound column to form a second-order combined parabolic surface, and the second-order combined parabolic surface forms the inner surface of the sound concentrating cover.

[0030] Correspondingly, if the second-order parabola is not set, the cross-section of the sound concentrating cover presents a first-order parabola. The acoustic center point of the medium and high-frequency sound column is at the focus of the first-order parabola. The opening width of the first-order parabola is equal to the wavelength corresponding to the crossover frequency between medium and low frequencies. The first-order parabola expands along the axis direction of the line source sound column to form a first-order parabolic surface, and the first-order parabolic surface forms the inner surface of the sound concentrating cover.

[0031] (5)Combined focusing. In actual assembly, on-site measurement and focusing should be carried out to ensure that the acoustic center F1 of the mid-high frequency horn is at the focus of the first-order parabola P1, and the acoustic center F2 of the low-frequency horn is at the focus of the second-order parabola P2. Correspondingly, with the fixed specifications of the sound-gathering cover, the positions of the mid-high frequency horn and the low-frequency horn can be finely adjusted to meet the focusing requirements.

[0032] (6)On-site measurement and confirmation. After on-site measurement of the sound pressure difference inside and outside the sound-gathering cover, when the design target is achieved, the design scheme can be confirmed, and mold opening and mass production can be carried out.

[0033] Figure 5 This is the sound pressure test curve of the sound field inside and outside the sound-gathering cover in an embodiment of the present invention. In the figure, curve A is the sound pressure test curve of the sound field inside the sound-gathering cover, and curve B is the sound pressure test curve of the sound field outside the sound-gathering cover. The test curve shows that: (1) The sound pressure of the sound field inside the sound-gathering cover is generally greater than that of the sound field outside the sound-gathering cover, indicating that the sound-gathering cover has the function of reducing sound leakage. (2) In specific frequency bands, such as the 5K to 10K Hz frequency band, the sound pressure of the sound field inside the sound-gathering cover is about 30 dB greater than that of the sound field outside the sound-gathering cover, indicating that the sound-gathering cover has a stronger ability to reduce sound leakage in this frequency band.

Claims

1. A sound amplification unit with a controllable sound field range, comprising a sound focusing enclosure and a line sound source sound column arranged in the sound focusing enclosure.

2. A sound amplification unit with controllable sound field range according to claim 1, characterized in that The line sound source sound column comprises a mid-high frequency sound column and a low frequency sound column arranged back to back, and the low frequency sound column faces the opening direction of the sound focusing cover.

3. A sound amplification unit with controllable sound field range according to claim 2, characterized in that The cross-section of the sound focusing cover presents a first-order parabola, the acoustic center point of the mid-high frequency sound column is at the focus of the first-order parabola, the opening width of the first-order parabola is equal to the wavelength corresponding to the mid-low frequency crossover frequency, and the first-order parabola expands along the axis direction of the linear sound source sound column to form a first-order parabola, and the first-order parabola constitutes the inner surface of the sound focusing cover.

4. A sound amplification unit with controllable sound field range according to claim 2, characterized in that The cross-section of the sound focusing cover presents a second-order combined parabola, the acoustic center point of the mid-high frequency sound column is at the focus of the first-order parabola, the opening width of the first-order parabola is equal to the wavelength corresponding to the mid-low frequency crossover frequency, the acoustic center of the low-frequency sound column is at the focus of the second-order parabola, the opening width of the second-order parabola is equal to the wavelength corresponding to the lower limit of the controllable frequency of the low-frequency sound column, the first-order parabola intersects with the second-order parabola at the intersection, the second-order combined parabola is composed of the first-order parabola before the intersection and the second-order parabola after the intersection, the second-order combined parabola expands along the axis direction of the linear sound source sound column to form a second-order combined parabola, and the second-order combined parabola constitutes the inner surface of the sound focusing cover.

Images