Acoustic device

Abstract

An acoustic device (1) is provided with: a housing (2); an acoustic tube (3) having an inner open end (31) that opens inside the housing (2) and an outer open end (32) that opens outside the housing (2), the acoustic tube (3) having a primary resonance frequency close to the frequency of a standing wave generated in the housing (2); and a sound absorbing material (4) which is provided in a region outside the acoustic tube (3) inside the housing (2), and which, when lambda is the wavelength of a resonance frequency that occurs due to the coupling between the primary resonance of the acoustic tube (3) and a standing wave generated in the housing (2), and lambda is the direction of propagation in which the standing wave propagates inside the housing (2), is the direction of propagation. The sound-absorbing material (4) is disposed at a position substantially lambda / 4 away from the first surface (21) of the housing (2) in the propagation direction.

Description

Technical Field

[0001] The invention relates to an audio device. Background Art

[0002] Patent Document 1 discloses a structure as an audio device such as a speaker, which includes: a frame having a space inside; and an acoustic tube (bass reflex port) having both ends opened, and the inside of the frame and the outside are connected through openings provided in the frame. In this audio device, it is possible to radiate sound having acoustic characteristics whose bass range is enhanced by the acoustic tube.

[0003] In an audio device having a housing, if a sound wave of a natural frequency is radiated into the interior of the housing, a standing wave of sound will be generated in the interior. This standing wave has an adverse effect on the acoustic characteristics of the audio device (the frequency characteristics of the sound radiated from the audio device), and is therefore not preferable.

[0004] In the acoustic device of Patent Document 1, the length of the acoustic tube is made substantially equal to the distance between a pair of opposing surfaces that are the inner surfaces of the housing, and the inner opening end of the acoustic tube that opens inside the housing is arranged near one of the pair of opposing surfaces. This reduces the occurrence of standing waves of sound generated inside the housing.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-139446 Summary of the invention

[0006] However, in an acoustic device having a housing and an acoustic tube, strong tube resonance (particularly primary resonance) occurs at a natural frequency of the acoustic tube corresponding to the length of the acoustic tube. The tube resonance of the acoustic tube adversely affects the acoustic characteristics of the acoustic device.

[0007] In order to suppress the tube resonance (especially the primary resonance) of the acoustic tube, it is conceivable to provide a sound absorbing material inside the acoustic tube, at the opening end of the acoustic tube and in its vicinity. However, in this case, there is a problem that the enhancement of the low frequency range (bass enhancement) achieved by the acoustic tube is hindered by the sound absorbing material.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an acoustic device capable of suppressing the interference of bass enhancement by an acoustic tube and suppressing the tube resonance of the acoustic tube.

[0009] One embodiment of the present invention is an acoustic device comprising: a frame; an acoustic tube having an inner opening end opened inside the frame and an outer opening end opened outside the frame and having a primary resonance frequency close to the frequency of a standing wave generated in the frame; and a sound absorbing material provided in a region outside the acoustic tube within the frame and arranged at a position approximately λ / 4 away from a first surface of the frame in the propagation direction when a wavelength of a resonance frequency generated due to coupling between the primary resonance of the acoustic tube and the standing wave generated in the frame is λ and a direction in which the standing wave propagates inside the frame is a propagation direction.

[0010] Effects of the Invention

[0011] According to the present invention, it is possible to suppress the obstruction of bass enhancement by the acoustic tube and to suppress the tube resonance of the acoustic tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a cross-sectional view showing an acoustic device according to one embodiment of the present invention.

[0013] Figure 2 yes Figure 1 Sectional view along line II-II.

[0014] Figure 3 It means from Figure 1 , 2 A diagram showing an example of standing waves generated by coupling between primary resonance of an acoustic tube and standing waves generated in a frame in an acoustic device without sound absorbing material.

[0015] Figure 4 Yes means Figure 1 , 2 A diagram showing an example of standing waves generated in a housing of an audio device. DETAILED DESCRIPTION

[0016] Below, refer to Figures 1 to 4 One embodiment of the present invention will be described.

[0017] The audio device 1 of this embodiment is a speaker such as a bass reflex speaker. Figure 1 , 2 As shown, the acoustic device 1 includes a housing 2, an acoustic tube 3, and a sound absorbing material 4. The acoustic device 1 of the present embodiment, which is a speaker, further includes a speaker unit (not shown).

[0018] The frame 2 is a box having a space inside. The appearance of the frame 2 and the specific shape of the space inside the frame 2 can be arbitrary. In the present embodiment, the space inside the frame 2 is formed into a rectangular parallelepiped. In addition, the appearance of the frame 2 is formed into a rectangular parallelepiped that is larger than the space inside the frame 2.

[0019] In the drawings, the Z-axis direction shows the direction in which the long side of the frame 2 extends. In addition, the X-axis direction shows the direction in which one short side of the frame 2 orthogonal to the long side extends, and the Y-axis direction shows the direction in which another short side of the frame 2 orthogonal to the long side and one short side extends.

[0020] The speaker unit is provided as a sound source in the housing 2. The sound generated in the speaker unit propagates to both the outside and the inside of the housing 2. The speaker unit generates sound of a predetermined frequency, thereby generating standing waves inside the housing 2 or primary resonance of the acoustic tube 3.

[0021] The acoustic tube 3 is a tube body that connects the space inside the frame 2 and the outside of the frame 2. The acoustic tube 3 has an inner open end 31 that opens inside the frame 2, and an outer open end 32 that opens outside the frame 2. In the present embodiment, the acoustic tube 3 extends from the inner surface of the frame 2 only to the inner side of the frame 2, and does not extend to the outside of the frame 2. Therefore, the inner open end 31 of the acoustic tube 3 is located in the space inside the frame 2, and the outer open end 32 of the acoustic tube 3 is located on the outer surface of the frame 2. In addition, the acoustic tube 3 may extend to both the inside and the outside of the frame 2, for example. That is, the outer open end 32 of the acoustic tube 3 may be located, for example, at a position away from the outer surface of the frame 2 to the outside.

[0022] The primary resonance frequency generated in the acoustic tube 3 is close to the frequency of the standing wave generated in the housing 2 .

[0023] Here, the "standing wave generated in the frame 2" is generated inside the frame 2 by superimposing a sound wave propagating from one of the two inner surfaces of the frame 2 opposite to each other to the other and a sound wave propagating from the other of the two inner surfaces to one. In the present embodiment, the standing wave generated in the frame 2 is a standing wave generated between the first surface 21 and the second surface 22 of the frame 2 opposite to each other in the Z-axis direction on the inner surface of the frame 2. The propagation direction of the standing wave generated in the frame 2 is the direction in which the first surface 21 and the second surface 22 are arranged, that is, the Z-axis direction. The first surface 21 and the second surface 22 of the frame 2 are the surfaces facing the inside of the frame 2 and are orthogonal to the propagation direction of the standing wave. In addition, the "standing wave generated in the frame 2" processed in the present embodiment is a primary standing wave.

[0024] exist Figure 4 The primary standing wave SW2 generated in the frame 2 is recorded. Figure 4In the , the speed of sound particles (sound pressure) is expressed by the shades of black and white. Figure 4 In the image, the faster the sound particles are (the lower the sound pressure is), the whiter they are, and the slower the sound particles are (the higher the sound pressure is), the darker they are. Figure 4 The whitest part among them indicates the position of the antinode (node ​​of sound pressure) of the acoustic particle velocity.

[0025] Furthermore, the frequency of the standing wave SW2 generated in the frame 2 and the primary resonance frequency of the acoustic tube 3 are preferably close to such an extent that the tube resonance of the acoustic tube 3 can be effectively suppressed by the sound absorbing material 4 described later. In order to effectively suppress the tube resonance of the acoustic tube 3 by the sound absorbing material 4, it is more preferable that the difference between the frequency of the standing wave SW2 generated in the frame 2 and the primary resonance frequency of the acoustic tube 3 is small. For example, the difference between the frequency of the standing wave SW2 of the frame 2 and the primary resonance frequency of the acoustic tube 3 is preferably 300 Hz or less, and more preferably 200 Hz or less.

[0026] In this embodiment, in order to make the frequency of the standing wave SW2 generated in the frame 2 and the primary resonance frequency of the acoustic tube 3 close to each other, Figure 1 The length L3 of the acoustic tube 3 (the length from the inner opening end 31 to the outer opening end 32) may be adjusted. Specifically, for example, the length L3 of the acoustic tube 3 may be adjusted to be close to the distance L2 between the first surface 21 and the second surface 22 of the frame 2.

[0027] In this embodiment, the inner open end 31 of the acoustic tube 3 is arranged to face the second surface 22 of the frame 2 in the Z-axis direction (the propagation direction of the standing wave SW2 generated in the frame 2). The acoustic tube 3 extends linearly from the first surface 21 of the frame 2 in the Z-axis direction.

[0028] In the structure composed of the frame 2 and the acoustic tube 3, a standing wave (hereinafter referred to as "coupled standing wave") is generated by coupling the primary resonance of the acoustic tube 3 and the standing wave SW2 of the frame 2. The resonance frequency of the coupled standing wave may be two. For example, when the resonance frequency of the primary standing wave of the frame 2 is 580 Hz and the primary resonance frequency of the acoustic tube 3 is 440 Hz, the resonance frequency of the coupled standing wave may be two, 400 Hz and 490 Hz.

[0029] exist Figure 3 An example of a standing wave SWC after coupling is described. Figure 3 In, with Figure 4 Similarly, the sound particle speed (sound pressure) is expressed by the shades of black and white. Figure 3The whitest part indicates the position of the antinode (sound pressure node) of the acoustic particle velocity in the coupled standing wave SWC. The antinode (sound pressure node) of the acoustic particle velocity in the coupled standing wave SWC is located in the area outside the acoustic tube 3 inside the frame 2. Figure 3 The resonance frequency of the standing wave SWC after coupling shown in the example is the lower frequency of the two resonance frequencies described above.

[0030] The inner opening end 31 of the acoustic tube 3 is preferably arranged at or near a position that becomes a node (antinode of sound pressure) of the acoustic particle velocity in the standing wave SW2 generated in the frame 2. For example, the inner opening end 31 of the acoustic tube 3 can be arranged near the first surface 21 or the second surface 22 of the frame 2 that becomes a node (antinode of sound pressure) of the acoustic particle velocity. Figure 1 , 3 In the embodiment, the inner opening end 31 is arranged near the second surface 22 of the frame 2. By arranging the inner opening end 31 of the acoustic tube 3 at such a position, the primary resonance of the acoustic tube 3 and the standing wave SW2 of the frame 2 are easily coupled, that is, the coupled standing wave SWC is easily generated.

[0031] Figure 1 The sound absorbing material 4 shown is provided to attenuate the coupled standing wave SWC. The sound absorbing material 4 can be made of a material suitable for attenuating sound waves, for example, a porous or elastic material such as sponge.

[0032] The sound absorbing material 4 is provided in the region outside the acoustic tube 3 within the frame 2. Figure 3 ) is set to λ, the sound absorbing material 4 is arranged at a position approximately λ / 4 away from the first surface 21 of the frame 2 in the Z-axis direction (the propagation direction of the standing wave SW2 generated in the frame 2). The position λ / 4 away from the first surface 21 corresponds to the position of the antinode (node ​​of sound pressure) of the acoustic particle velocity in the standing wave SWC after coupling. The position approximately λ / 4 away from the first surface 21 can be, for example, in the range of about ±20% of λ / 4 with the position λ / 4 away from the first surface 21 as the center.

[0033] As described above, there are two resonance frequencies in the coupled standing wave SWC, but in this embodiment, the sound absorbing material 4 is arranged at a position corresponding to a lower resonance frequency. Alternatively, the sound absorbing material 4 may be arranged at a position corresponding to a higher resonance frequency, for example.

[0034] In addition, the sound absorbing material 4 is located between the first surface 21 and the inner opening end 31 in the Z-axis direction. That is, the sound absorbing material 4 is not arranged on the opening side of the inner opening end 31 in the Z-axis direction.

[0035] Furthermore, the sound absorbing material 4 of this embodiment is arranged so as to divide the space inside the frame 2 into a region on the first surface 21 side and a region on the second surface 22 side in the Z-axis direction. Figure 2 As shown, the sound absorbing material 4 is arranged over the entire circumferential direction and the entire radial direction of the acoustic tube 3 when the acoustic tube 3 is viewed from the Z-axis direction.

[0036] In addition, the sound absorbing material 4 may not divide the space inside the frame 2 into two regions, for example. In this case, a hole penetrating in the Z-axis direction, for example, may be formed in the sound absorbing material 4. In addition, the sound absorbing material 4 may be formed only in a part of the circumferential direction of the acoustic tube 3, or may be formed only in a part of the radial direction of the acoustic tube 3.

[0037] As described above, in the acoustic device 1 of the present embodiment, the sound absorbing material 4 is disposed at a position approximately λ / 4 wavelength away from the first surface 21 of the frame 2 within the frame 2. λ is the wavelength of the resonance frequency of the standing wave SWC generated by coupling between the primary resonance of the acoustic tube 3 and the standing wave SW2 generated in the frame 2. Therefore, the coupled standing wave SWC can be attenuated by the sound absorbing material 4. Thus, the tube resonance (primary resonance) of the acoustic tube 3 can be suppressed.

[0038] Furthermore, by arranging the sound absorbing material 4 at the above position, it is possible to avoid arranging the sound absorbing material 4 inside the acoustic tube 3 or near the inner opening end 31 or the outer opening end 32 of the acoustic tube 3. Thus, it is possible to prevent the sound absorbing material 4 from hindering the bass enhancement achieved by the acoustic tube 3.

[0039] In the acoustic device 1 of the present embodiment, the inner opening end 31 of the acoustic tube 3 is located at a position opposite to the second surface 22 of the frame 2 in the Z-axis direction (the propagation direction of the standing wave SW2 generated in the frame 2). On this basis, the sound absorbing material 4 is located between the first surface 21 of the frame 2 and the inner opening end 31 in the Z-axis direction. Thus, it is possible to reliably prevent the sound absorbing material 4 from being arranged opposite to the inner opening end 31 of the acoustic tube 3. Therefore, it is possible to more effectively suppress the sound absorbing material 4 from hindering the bass enhancement achieved by the acoustic tube 3.

[0040] In the acoustic device 1 of the present embodiment, the acoustic tube 3 extends linearly along the Z-axis direction from the first surface 21 of the frame 2. Therefore, the acoustic tube 3 does not intersect the propagation direction of the standing wave SW2 generated in the frame 2 in the interior of the frame 2. Therefore, it is possible to effectively suppress the standing wave SW2 generated in the frame 2 from changing randomly depending on the position of the acoustic tube 3 arranged in the interior of the frame 2. Thus, the position of the sound absorbing material 4 for suppressing the tube resonance of the acoustic tube 3 can be easily set.

[0041] As mentioned above, although this invention was demonstrated in detail, this invention is not limited to the said embodiment, Various changes can be added within the range which does not deviate from the summary of this invention.

[0042] In the present invention, the frequency of the "standing wave generated in the housing 2" that is close to the primary resonance frequency generated in the acoustic tube 3 is not limited to the frequency of the primary standing wave SW2, and may be, for example, the frequency of a secondary standing wave. Even if the "standing wave generated in the housing 2" is a secondary standing wave, when the secondary standing wave generated in the housing 2 is coupled to the primary resonance of the acoustic tube 3, the tube resonance of the acoustic tube 3 can be suppressed by arranging the sound absorbing material 4 at a position corresponding to the resonance frequency of the standing wave SWC after coupling, as in the above-mentioned embodiment.

[0043] In the present invention, the acoustic tube 3 may be bent inside the frame 2, for example. In this case, the inner surface of the frame 2 connected to the acoustic tube 3 is not limited to the first surface 21 and the second surface 22 of the frame 2 arranged in the propagation direction of the standing wave, and may be, for example, a surface intersecting or adjacent to the first surface 21 and the second surface 22. However, the inner open end 31 of the acoustic tube 3 is preferably opposed to the first surface 21 or the second surface 22 of the frame 2 in the propagation direction of the standing wave SW2 of the frame 2.

[0044] Description of the label

[0045] 1 ... audio device, 2 ... housing, 21 ... first surface, 22 ... second surface, 3 ... audio tube, 31 ... inner opening end, 32 ... outer opening end, 4 ... sound absorbing material.

Claims

1. An audio device, comprising: Frame; an acoustic tube having an inner opening end opened inside the frame and an outer opening end opened outside the frame, and having a primary resonance frequency close to a frequency of a standing wave generated in the frame; and a sound absorbing material provided in a region outside the acoustic tube within the frame, and arranged at a position approximately λ / 4 away from a first surface of the frame in the propagation direction when a wavelength of a resonance frequency generated by coupling between a primary resonance of the acoustic tube and a standing wave generated in the frame is defined as λ and a direction in which the standing wave propagates within the frame is defined as a propagation direction.

2. The audio device according to claim 1, wherein: The frame has a second surface opposite to the first surface in the propagation direction, The inner opening end is located at a position opposite to the second surface in the propagation direction. The sound absorbing material is located between the first surface and the inner opening end in the propagation direction.

3. The audio device according to claim 1 or 2, wherein: The acoustic tube extends linearly from the first surface along the propagation direction inside the housing.

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