JP6465096B2 - Sound equipment - Google Patents

Description

  The present invention relates to a technique for suppressing standing waves using tube resonance.

  In spaces surrounded by walls in acoustic equipment, standing waves are generated by the reciprocation of sound waves between the walls of the space when sound waves with natural frequencies are radiated in the space, which adversely affects the acoustic characteristics. It has been known. Patent Documents 1 to 3 disclose a technique for suppressing a standing wave in a speaker that is one of acoustic devices. The speaker device disclosed in Patent Literature 1 includes a speaker unit, a cabinet incorporating the speaker unit, and a Helmholtz resonator provided inside the cabinet. In this speaker device, the neck length L and the cavity volume V are designed so that the Helmholtz resonator resonates at the same frequency as the standing wave generated in the cabinet. According to this speaker device, when a standing wave is generated in the cabinet, the Helmholtz resonator exhibits a resonance phenomenon, and the standing wave is attenuated by the resonance phenomenon. The speaker device disclosed in Patent Document 2 includes a speaker unit, a cabinet incorporating the speaker unit, and an acoustic tube (closed tube) having an open end and a closed end. The acoustic tube of this speaker device has a tube length L that is ¼ times the lowest resonance mode of a standing wave generated in the cabinet. The acoustic tube is housed in the cabinet in such a posture that the position of the open end is close to the position of the antinode (particle velocity node) of the sound pressure of the standing wave in the cabinet. In this speaker device, when a standing wave (standing wave having a wavelength four times the tube length L) is generated in the cabinet, a resonance wave is generated in the acoustic tube. This resonance wave has a sound pressure node (particle velocity antinode) at the open end of the acoustic tube and a sound pressure antinode (particle velocity antinode) at the closed end. Therefore, according to this speaker device, the deviation of the sound pressure distribution in the cabinet is alleviated, and the standing wave in the cabinet is attenuated. Patent Document 3 also discloses the same technology as Patent Document 2.

Japanese Patent No. 2606447 Japanese Patent No. 3766682 JP 2008-131199 A

  The techniques of Patent Documents 2 and 3 match the position of the antinode of the standing wave in the space with the position of the node of the resonance wave in the acoustic tube, and by relaxing the sound pressure distribution in the space at this position, It is to reduce. Therefore, even if the acoustic tube contained in the space is not a closed tube but an open tube (a tube open on both sides), the position of the antinode of the standing wave in the space and the position of the node of the resonance wave in the open tube As long as the open tubes can be arranged so as to match, the same effects as the techniques of Patent Documents 2 and 3 should be obtained, but such a technique has not yet been put into practical use.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a technical means for suppressing standing waves generated in a space by utilizing tube resonance of an open tube.

The present invention includes an acoustic device comprising a housing that encloses a space surrounded by at least a pair of opposed surfaces, and an open tube having first and second open ends positioned in the space. I will provide a.

  According to the present invention, when a standing wave is generated in the space, a standing wave that cannot coexist with the standing wave is generated in the open tube, so that the standing wave generated in the space is reduced.

In a preferred aspect, the first opening end is located in the vicinity of one of the opposing surfaces of the pair of opposing surfaces, and the second opening end is located substantially at the center between the pair of opposing surfaces.

In another preferred aspect, the open tube has a tube length longer than a distance between the first open end and the second open end in a direction from one of the pair of opposed surfaces to the other. For example, the open tube has a tube length that is approximately twice the distance between the first open end and the second open end in the direction from one of the pair of opposed surfaces to the other.

In another preferable aspect , the acoustic device includes a housing containing a space surrounded by at least a pair of opposed surfaces, and first and second openings located in the vicinity of one opposed surface between the pair of opposed surfaces. And an open tube having an end. In a preferred embodiment, the open tube has a tube length substantially equal to the distance between the pair of opposed surfaces.

In another preferred embodiment, the open tube has a bent shape or a spiral shape. A part of the open tube may be outside the space.

It is a front view of the speaker which is an example of 1st Embodiment of this invention. It is a front view of the speaker which is an example of 1st Embodiment of this invention. It is a figure which shows the frequency response which is the 1st verification result of the effect of the speaker. It is a figure which shows the positional relationship of the standing wave and the opening end of an open tube in the speaker. It is a figure which shows the waveform of the resonant wave in the open tube of the speaker. It is a figure which shows the frequency response which is a verification result of the 2nd verification of the effect of the speaker. It is a perspective view of the bass reflex type speaker created for the 3rd verification of the effect of the speaker. It is a figure which shows the frequency response which is a verification result of the 3rd verification of the effect of the speaker. It is a figure which shows the frequency response which is a verification result of the 3rd verification of the effect of the speaker. It is a figure which shows the frequency response which is a verification result of the 3rd verification of the effect of the speaker. It is a front view of the speaker which is an example of 2nd Embodiment of this invention. It is a figure which shows the frequency response which is a verification result of the effect of the speaker. It is a figure which shows the positional relationship of the standing wave and the opening end of an open tube in the speaker. It is a figure which shows the waveform of the resonant wave in the open tube of the speaker. It is a front view of the speaker which is 3rd Embodiment of this invention. It is a figure which shows the frequency response which is the verification result of the speaker. It is a front view of the speaker which is 4th Embodiment of this invention. It is a figure which shows the frequency response which is the verification result of the speaker. It is a figure which shows the frequency response which is the verification result of the speaker. It is a figure which shows the frequency response which is the verification result of the speaker. It is a front view of the speaker which is other embodiment of this invention. It is a figure which shows typically and comprehensively the relationship between the standing wave which generate | occur | produces in the space in a housing | casing, and an open tube in the audio equipment by this invention.

Embodiments of the present invention will be described below with reference to the drawings.
<First Embodiment>
FIG. 1A is a front view of a speaker 9 which is an acoustic device according to the first embodiment of the present invention. The speaker 9 includes a cabinet 1, a speaker unit 2 fixed to the outside of the cabinet 1, and an open tube 10 accommodated in a space S in the cabinet 1. The cabinet 1 is a member that serves as a housing for the speaker 9. The cabinet 1 has a hollow rectangular parallelepiped shape surrounded by wall surfaces 4U and 4D facing in the vertical direction, wall surfaces 4F and 4B facing in the front-rear direction, and wall surfaces 4L and 4R facing in the left-right direction. The vertical width H (the distance between the wall surfaces 4U and 4D: for example, H = 1050 mm) in the space S in the cabinet 1 is the depth width L (the distance between the wall surfaces 4F and 4B: for example, L = 200 mm) or It is sufficiently larger than the left-right width W (distance between the wall surfaces 4L and 4R: for example, W = 300 mm).

The speaker unit 2 is a device that serves as a sound source in the speaker 9. The speaker unit 2 is embedded in the approximate center of the wall surface 4U of the cabinet 1 with the sound emitting surface facing outward. An electric signal is input to the speaker unit 2 from an audio device (not shown). The speaker unit 2 radiates this electric signal as a sound wave. Here, when a sound wave having the same frequency as the natural frequency is transmitted from the speaker unit 2 to the space S, the sound wave reciprocates between the wall surfaces 4U and 4D of the space S and a plurality of sound waves reciprocating between the wall surfaces 4U and 4D are combined. The standing wave SW _k (k = 1, 2,...) Having a wavelength λ _k (k = 1, 2,...) Times 2 / k (k = 1, 2,...) Times the distance between the wall surfaces 4U and 4D. Occur.

The open tube 10 is a member that plays a role of reducing the standing wave SW _k . This open tube 10 has a tube length corresponding to approximately the half wavelength of the lowest-order standing wave SW _{k to be} suppressed (in the example of FIG. 1A, the primary standing wave SW ₁ ). ing. The open tube 10 has a J-shape bent 90 degrees at two points on the way from one open end 11 to the other open end 12. The open tube 10 is housed in the space S in a posture that satisfies the following two conditions a1 and b1.
a1. One open end 11 and the other open end 12 are arranged at the position of the approximately antinode LP and the position of the approximate node ND of the sound pressure of the lowest order among the standing waves SW _{k to be} suppressed in the space S. B1. One opening end 11 and the other opening end 12 are arranged at respective positions separated by approximately one quarter wavelength of the standing wave SW _{k in} the facing direction of the two facing surfaces of the wall surfaces 4U and 4D in the space S. To be done

The above is the detail of the structure of the speaker 9 which is this embodiment. In the example of FIG. 1 (A), 1-order open end position of the antinode LP _1-1 of the side wall 4U of the two antinodes LP _1-1 and LP _1-2 of the standing wave SW ₁ 11 is disposed, and the open end 12 is disposed at the position of the node ND _1-1 between the two antinodes LP _1-1 and LP _1-2 . However, as shown in the example of FIG. 1B, the opening end 11 is arranged at the position of the belly LP _1-2 on the wall surface 4D side, and the opening end 12 is arranged at the position of the node ND _1-1. It may be a proper posture. By placing the open tube 10 in the space S in the posture as shown in FIGS. 1A and 1B, the first-order or higher-order standing wave SW _k in the space S can be reduced. Further, as is well known, there is a sound source at the position of the node ND _1-1 of the primary standing wave SW _{1 on} the wall surfaces 4U, 4D, 4L, 4R, 4F, 4B forming the cabinet 1 of the speaker 9. In this case, the odd-order standing waves SW ₁ , SW ₃ , SW ₅ ... In the space S are suppressed by the vibration of the sound source (see Patent Document 3 for details). Therefore, as the speaker 9A of the example of FIG. 2, the primary of which is the speaker unit 2 in the positions of the nodes ND _1-1 of the standing wave SW _1, 2-order standing wave SW ₂ of approximately half The open tube 20 having a tube length corresponding to the wavelength may be accommodated in the space S in such a posture as to satisfy the above-described conditions a1 and b1. Even when the open tube 20 is accommodated in the space S in such a posture, the first-order or higher-order standing wave SW _k in the space S can be reduced.

  Here, the inventors performed three verifications for confirming the effect of the present embodiment. First, the contents of the first verification will be described. In the first verification, the inventors input a test sound signal ST (for example, white noise) to the speaker unit 2 for the speaker 9 in the example of FIG. The input signal ST when measured at the measurement point P in the space S (more specifically, the measurement point P in the vicinity of the inside of the position where the wall surfaces 4D, 4B, and 4R intersect (see FIG. 1A)). The frequency response R-9, which is the spectral difference of the measurement signal SM, was calculated by simulation. Similarly, for the speaker 9 ′ in which the open tube 10 is removed from the speaker 9, the input signal when the test sound signal ST is input to the speaker unit 2 and the sound wave radiated from the speaker unit 2 is measured at the measurement point P is input. The frequency response R-9 ′, which is the difference in spectrum between the ST and the measurement signal SM, was calculated by simulation. FIG. 3 shows the frequency responses R-9 and R-9 'with the frequency axes aligned.

Referring to FIG. 3, peaks appear in the vicinity of 160 Hz, 320 Hz, 480 Hz, 650 Hz, 820 Hz, and 960 Hz in both frequency responses R-9 and R-9 ′. In the frequency response R-9, although the amplitude of the peak near 650 Hz is substantially the same as that of the frequency response R-9 ′, the amplitude of peaks near 160 Hz, 320 Hz, 480 Hz, 820 Hz, and 970 Hz is the frequency response R−. It is smaller than 9 '. In the frequency response R-9, peaks near 160 Hz, 320 Hz, 480 Hz, 820 Hz, and 970 Hz are broken. From this, the first-order standing wave SW ₁ (160 Hz), the second-order standing wave SW ₂ (320 Hz), the third-order standing wave SW ₃ (480 Hz), and the fifth-order standing wave SW ₁ (160 Hz) in the space S by the speaker 9. It was confirmed that the standing wave SW ₅ (820 Hz) and the sixth-order standing wave SW ₆ (970 Hz) can be suppressed.

The inventors suppress the standing waves SW ₁ , SW ₂ , SW ₃ , SW ₅ , SW ₆ except the fourth order by the speaker 9 in the example of FIG. 1A based on the verification result of the first verification. I guessed the reason for being as follows. As shown in FIG. 4, in the speaker 9, the open end 11 of the open tube 10 in the space S is disposed at the position of the antinode LP _1-1 of the standing wave SW ₁ . Position belly LP _1-1 of the standing wave SW ₁ is secondary and subsequent standing wave _{SW 2, SW 3, SW 4} , SW 5 ... belly LP _2-1 of, LP _3-1, LP _{4- 1} , LP _5-1 . Further, the open end 12 of the open tube 10 in the space S is arranged at the position of the node ND _1-1 of the standing wave SW ₁ . The position of the node ND _1-1 of the standing wave SW ₁ is the second and subsequent even standing waves SW ₂ and SW ₄ , the antinodes LP _2-2 and LP _4-3 , and the third and subsequent odd orders. This corresponds to the nodes ND _3-2 and ND _5-3 of the standing waves SW ₃ and SW ₅ . Therefore, when the standing wave SW _k (k = 1, 2,...) Is generated in the space S, the medium (air) in the vicinity of the open end 11 of the open tube 10 is an odd-order and even-order standing wave SW _k. is vibrated by sound pressure changes the position of the belly LP of the medium in the vicinity of the open end 12 (air) is vibrated by the sound pressure changes the position of the antinodes LP even order standing wave SW _k.

Here, focusing on the relationship between the primary standing wave SW ₁ in the space S and the behavior of the medium (air) in the open tube 10, the medium (air) in the vicinity of the open end 11 in the open tube 10. Is excited by the sound pressure change of the antinode LP _1-1 of the standing wave SW ₁ , and a traveling wave TW ₁ from the opening end 11 toward the opening end 12 is generated. This traveling wave TW ₁ travels through the open tube 10 and reaches the open end 12. Since the position where the opening end 12 of the open tube 10 in the space S is arranged is the position of the node ND _1-1 of the standing wave SW ₁ , the opening end 12 even when the traveling wave TW ₁ reaches the opening end 12. The medium (air) in the vicinity of is hardly vibrated. For this reason, when the traveling wave TW ₁ reaches the opening end 12, a reflected wave RW ₁ is generated at the opening end 12. When this reflected wave RW ₁ and the traveling wave TW ₁ is synthesized in the open tube 10, the resonance wave XW ₁ having the same wavelength lambda ₁ and the standing wave SW ₁ is generated. The resonance wave XW _1, since it is those Deki by combining the traveling wave TW ₁ reflected wave RW ₁ in which the traveling wave TW ₁ of Toko is reflected by the open end 12, as shown in FIG. 5 (A) In the resonance wave XW _1, the opening end 11 side and the opening end 12 side each become a node ND. For this reason, the sound pressure distribution of the standing wave SW ₁ is relaxed at the position of the opening end 11. The inventors presumed that the standing wave SW ₁ was attenuated for the reasons described above. Further, the presence of the node ND at the position of the opening end 12 is the same for all the standing waves SW _k of the odd order. Accordingly, the inventors speculated that odd-order standing waves SW ₃ , SW ₅ , SW ₇ ... Of the third order or higher are also attenuated for the same reason as the standing wave SW ₁ .

Next, paying attention to the relationship between the secondary standing wave SW ₂ in the space S and the behavior of the medium (air) in the open tube 10, the medium (near the open ends 11 and 12) in the open tube 10 ( air) is vibrated by sound pressure changes of abdominal LP _2-1 and LP _2-2 of the standing wave SW _2, the traveling wave TW ₂ traveling direction from each other with a phase difference of π therebetween in reverse And TW ₂ ″ are generated. The traveling waves TW ₂ and TW ₂ ″ have a phase difference of π because the sound pressure of two adjacent antinodes LP in the standing wave _k has a phase difference of π. Because it has changed. When the traveling wave TW ₂ and TW ₂ "is synthesized in open tube 10, the resonance wave XW ₂ having the same wavelength lambda ₂ and the standing wave SW ₂ occurs. The resonance wave XW ₂ is a π Since the traveling waves TW ₂ and TW ₂ ″ having a phase difference are synthesized, as shown in FIG. 5B, the center between the open ends 11 and 12 in the resonance wave XW ₂ is a node ND. become. Further, since the tube length of the open tube 10 (the tube length corresponding to the half wavelength of the primary standing wave SW ₁ ) is the same as the wavelength λ ₂ (λ ₂ = λ _1/2 ) of the standing wave SW ₂ , the open end If the middle between 11 and 12 becomes a node ND, the side of the open ends 11 and 12 also becomes a node ND. For this reason, the sound pressure distribution of the standing wave SW ₂ is relaxed at the positions of the open ends 11 and 12. The inventors have speculated that the standing wave SW ₂ is attenuated for the reasons described above. Further, the sound pressure at the position of the opening end 11 and the sound pressure at the position of the opening end 12 change with a phase difference of π also for the sixth-order standing wave SW ₆ and the tenth-order standing wave SW ₁₀ . It is the same. Therefore, the inventors speculated that the sixth-order standing wave SW ₆ and the tenth-order standing wave SW ₁₀ are also attenuated for the same reason as the second-order standing wave SW ₂ .

Next, paying attention to the relationship between the fourth-order standing wave SW ₄ in the space S and the behavior of the medium (air) in the open tube 10, the medium (near the open ends 11 and 12 in the open tube 10 ( Air) is vibrated by the sound pressure change of the antinodes LP _4-1 and _4-2 of the standing wave SW ₄ , and the traveling waves TW ₄ and TW ₄ ′ having the same phase and opposite traveling directions are generated. . The traveling waves TW ₄ and TW ₄ ′ have the same phase because the sound pressures of the two antinodes LP separated by sandwiching one antinode LP in the standing wave SW _k change in the same phase. Because. When the traveling wave TW ₄ and TW ₄ 'is synthesized in open tube 10, the resonance wave XW ₄ having the same wavelength lambda ₄ and standing wave SW ₄ is generated. Since this resonance wave XW ₄ is formed by synthesizing traveling waves TW ₄ and TW ₄ ′ having the same phase, as shown in FIG. 5 (C), between the open ends 11 and 12 of this resonance wave XW ₄ The middle of becomes a belly LP. Further, (tube length of a half wavelength of the first order standing wave SW ₁₎ pipe length open tube 10 since it is twice the wavelength lambda ₄ standing wave _{SW 4 (λ 4 = λ 1} /4), the opening If the middle between the ends 11 and 12 becomes an antinode LP, the side of the open ends 11 and 12 also becomes an antinode LP. For this reason, the sound pressure distribution of the standing wave SW ₄ is not relaxed at the positions of the open ends 11 and 12. The inventors speculated that the attenuation was not caused only by the fourth-order standing wave SW ₄ because of the above reason. Further, it is the same for eighth-order standing wave SW ₈ the sound pressure of the position of the sound pressure and the open end 12 of the position of the opening end 11 is varied in the same phase. Therefore, the inventors speculated that the eighth-order standing wave SW ₈ is not attenuated for the same reason as the fourth-order standing wave SW ₄ .

  Next, the contents of the second verification will be described. In the second verification, the inventors input a test sound signal ST to the speaker unit 2 for the speaker 9A shown in FIG. Specifically, the frequency response R, which is the difference between the spectrum of the input signal ST and the measurement signal SM when measured at the measurement point P (see FIG. 2) near the inside of the position where the wall surfaces 4D, 4B, and 4R intersect. -9A was calculated by simulation. Similarly, for the speaker 9A ′ in which the open tube 10 is removed from the speaker 9A, the input signal when the test sound signal ST is input to the speaker unit 2 and the sound wave radiated from the speaker unit 2 is measured at the measurement point P is input. The frequency response R-9A ′, which is the difference in spectrum between the ST and the measurement signal SM, was calculated by simulation. FIG. 6 shows the frequency responses R-9A and R-9A 'with the frequency axes aligned.

Referring to FIG. 6, in both frequency responses R-9A and R-9A ′, peaks appear in the vicinity of 160 Hz, 320 Hz, 480 Hz, 650 Hz, 820 Hz, and 970 Hz, but in frequency response R-9A, 160 Hz, The amplitude of peaks near 320 Hz, 480 Hz, 650 Hz, 820 Hz, and 970 Hz is smaller than that of the frequency response 9-A ′. In the frequency response R-9A, peaks near 320 Hz, 480 Hz, 650 Hz, 820 Hz, and 970 Hz are broken. Therefore, it was confirmed that can suppress the standing wave _SW 1 to SW ₆ to 1 through the sixth-order in the space S by the speaker 9A.

Next, the contents of the third verification will be described. In the third verification, the inventors measured the frequency response of an open tube having a tube length corresponding to about a half wavelength of the secondary standing wave SW _{2 in} a bass reflex type speaker. More specifically, as shown in FIG. 7, the space S (longitudinal width H (H = 1050 mm), lateral width W (W = 200 mm), depth L (L = 300 mm) of the bass reflex type speaker SP _BS is shown. the open tube OP secondary approximately half wavelength of the pipe length of the standing wave SW ₂ in the space S) of dimension those housed in a posture that satisfies the above conditions a1 and b1 and speaker 9A _BS. A speaker 9A _BS ′ is obtained by removing the open tube OP from the speaker 9A _BS .

Then, the position near the front of the center speaker unit SU _CNT in the speakers 9A _BS and 9A _BS ′ is defined as the first measurement point P-1, and the position near the front of the bass reflex port BP in the speakers 9A _BS and 9A _BS ′. _{Was set} as a second measurement point P-2, and a position inside the substantially center of the wall surface opposite to the side where the speaker unit _SUCNT is located was set as a third measurement point P-3. Then, sound signals are input to the speaker units SU _CNT of the speakers 9A and 9A ′, and sound waves radiated from the speaker units SU _CNT according to the sound signals are measured at the measurement points P-1, P-2, and P-3. did.

Then, the speaker _{9A BS,} which is the difference between the spectrum of the measurement signal SM of the speaker units _SU measuring points P-1 and the input signal ST of the _{CNT, P-2, P-} 3 frequency response _R 1 _-9A BS, _{R 2} - 9A _BS, was calculated _R 3 _{-9A BS.} Speaker _{9A BS} 'Similarly, the speaker units _SU measuring points P-1 and the input signal ST of the _CNT, P-2, which is the difference between the spectrum of the measurement signal SM at P-3 frequency response _R 1 _{-9A BS',} R ₂ -9A _BS 'and R ₃ -9A _BS ' were calculated. FIG. 8 shows the frequency responses R ₁ -9A _BS and R ₁ -9A _BS 'with the frequency axes aligned. FIG. 9 shows the frequency responses R ₂ -9A _BS and R ₂ -9A _BS ′ with the frequency axes aligned. Figure 10 is a diagram showing align the frequency axis frequency response _R 3 _{-9a BS} and _R 3 _{-9A BS} '.

8, 9, the frequency response _R 1 _{-9a BS} in FIG. _{10 ', R 2 -9A BS'} , the R 3 _{-9A BS} ', the peak occurs in the vicinity of 300 Hz. This indicates that the secondary standing wave SW ₂ cannot be effectively suppressed by resonance of the bass reflex port BP in the bass reflex speaker SP _BS . On the other hand, in the frequency responses R ₁ -9A _BS , R ₂ -9A _BS , R ₃ -9A _BS , the peak is broken into two near 300 Hz, and the amplitude of each frequency response R ₁ -9A _BS ', It is smaller than that of R ₂ -9A _BS 'and R ₃ -9A _BS '. Therefore, it was confirmed that can suppress the second-order standing wave SW ₂ is a suppression target the speaker 9A _BS.

Here, in the second verification the verification results described above (Fig. 6), whereas it was confirmed that can suppress the standing wave SW ₁ to SW ₆ to 1 through the sixth order, verify the third check In the results (FIGS. 8, 9, and 10), it was not confirmed that the _{third to sixth} higher-order standing waves SW _{3 to} SW ₆ could be suppressed. The inventors presumed this reason as follows. If the inside of the speaker 9A _BS is a completely sealed space, the wavelengths λ ₂ , λ ₃ , λ ₄ ... Of the standing waves SW ₂ , SW ₃ , SW ₄ . This coincides with an integral multiple of the wavelength λ ₁ of the wave SW ₁ . However, when there is an additional element such as the bass reflex port BP of the speaker 9A _BS , λ ₂ , λ ₃ , and λ ₄ of the secondary and subsequent standing waves SW ₂ , SW ₃ , SW ₄ . there is a case that does not match an integer multiple of the SW _1. On the other hand, the wavelengths of the secondary and subsequent resonance waves XW ₂ , XW ₃ , XW ₄ ... In the open tube OP of the speaker 9A _BS always coincide with an integral multiple of the primary resonance wave XW ₁ . For this reason, in the speaker 9A _BS , a frequency mismatch may occur between the high-order standing wave SW and the resonance wave XW. The inventors speculated that the _{third to sixth} standing waves SW _{3 to} SW ₆ were not suppressed in the speaker 9A _BS for the above reasons.

Second Embodiment
FIG. 11A is a front view of a speaker 9B which is an acoustic device according to the second embodiment of the present invention. This speaker 9B is a space S of the cabinet 1 in the speaker 9 (first embodiment) (a hollow space S surrounded by three pairs of opposing surfaces of the wall surfaces 4U and 4D, the wall surfaces 4F and 4B, and the wall surfaces 4L and 4R). The open tube 10 is replaced with the open tube 30. This open tube 30 has a tube length corresponding to approximately a half wavelength of the primary standing wave SW ₁ . The open tube 30 is U-shaped. And this open tube 30 is stored in the space S in the attitude | position which satisfy | fills the conditions c1 shown below.
c1. The open ends 31 and 32 of the open tube 30 are arranged at or near the position of the same antinode LP of the lowest-order standing wave SW _{k to be} suppressed in the space S.

The above is the details of the configuration of the speaker 9B according to the present embodiment. Here, in the example of FIG. 11 (A), 1-order open end position of the antinode LP _1-1 of the side wall 4U of the two antinodes LP _1-1 and LP _1-2 of the standing wave SW ₁ 31 and 32 are arranged. However, as shown in the example in FIG. 11 (B), it may be position as the open end 31 and 32 is placed at the position of antinode LP _1-2 of the side wall 4D. By placing the open tube 30 in the space S in a posture as shown in FIG. 11A or FIG. 11B, the first-order or higher standing wave SW _k in the space S can be reduced.

  Inventors performed the following verification in order to confirm the effect of this embodiment. The inventors input the test sound signal ST to the speaker unit 2 for the speaker 9B in the example of FIG. 11A, and the sound wave radiated from the speaker unit 2 is measured at the measurement point P in the space S (more specifically, Is a frequency response R that is the difference between the spectrum of the input signal ST and the measurement signal SM when measured at the measurement point P (see FIG. 11A) near the inside of the position where the wall surfaces 4D, 4B, and 4R intersect. -9B was calculated by simulation. Similarly, the input signal when the test sound signal ST is input to the speaker unit 2 and the sound wave radiated from the speaker unit 2 is measured at the measurement point P also for the speaker 9B ′ from which the open tube 30 is removed from the speaker 9B. The frequency response R-9B ′, which is the difference between the spectrum of ST and the measurement signal SM, was calculated by simulation. FIG. 12 shows the frequency responses R-9B and R-9B 'with the frequency axes aligned.

Referring to FIG. 12, peaks appear in the vicinity of 160 Hz, 320 Hz, 480 Hz, 650 Hz, 820 Hz, and 970 Hz in both frequency responses R-9B and R-9B ′. In the frequency response R-9B, the amplitudes of peaks near 320 Hz, 650 Hz, and 970 Hz are almost the same as those of the frequency response R-9B ′, but the amplitudes of peaks near 160 Hz, 480 Hz, and 820 Hz are the frequency response R− It is smaller than that of 9B ′. In the frequency response R-9B, peaks near 160 Hz, 480 Hz, and 820 Hz are broken. From this, according to the speaker 9B, the first-order standing wave SW ₁ (160 Hz), the third-order standing wave SW ₃ (480 Hz), and the fifth-order standing wave SW ₅ (820 Hz) in the space S can be suppressed. Was confirmed.

Based on this verification result, the inventors speculated as follows why the standing waves SW ₁ , SW ₃ , and SW ₅ are suppressed in the space S of the speaker 9B. As shown in FIG. 13, in the speaker 9 </ b> B, both the two open ends 31 and 32 of the open tube 30 in the space S are arranged at the position of the antinode LP _1-1 of the standing wave SW ₁ . The position of antinode LP _1-1 of the standing wave SW ₁ is secondary and subsequent standing wave _{SW 2, SW 3, SW 4} , SW 5, SW 6 ... belly LP _2-1 of, LP _3-1, It corresponds to _LP4-1 , _LP5-1 ... Therefore, when the standing wave SW _k (k = 1, 2,...) Is generated in the space S, the medium (air) in the vicinity of the open ends 31 and 32 of the open tube 30 is the antinode LP of each standing wave SW _k . Is excited by a change in sound pressure at the position of.

Here, paying attention to the relationship between the primary standing wave SW ₁ in the space S and the behavior of the medium (air) in the open tube 30, the medium (near the open ends 31 and 32 in the open tube 30 ( Air) is vibrated by a change in the sound pressure of the antinode LP _1-1 of the standing wave SW ₁ , and traveling waves TW ₁ and TW ₁ ′ having opposite phases and the same phase are generated. The traveling waves TW ₁ and TW ₁ ′ have the same phase because the sources of the traveling waves TW ₁ and TW ₁ ′ are the same. When the traveling wave TW ₁ and TW ₁ 'is synthesized in open tube 30, the resonance wave XW ₁ having the same wavelength lambda ₁ and the standing wave SW ₁ is generated. Since this resonance wave XW ₁ is formed by synthesizing traveling waves TW ₁ and TW ₁ ′ having the same phase, as shown in FIG. 14 (A), between the open ends 31 and 32 of this resonance wave XW ₁ The middle of becomes a belly LP. Since the tube length of the open tube 30 is the same as the length λ _{1/2 corresponding} to a half wavelength of the standing wave XW ₁ , when the middle between the open ends 31 and 32 becomes an antinode LP, the open ends 31 and 32 side is a node. Become ND. For this reason, the sound pressure distribution of the standing wave SW ₁ is relaxed at the positions of the open ends 31 and 32. The inventors speculated that the standing wave SW ₁ was attenuated for the above reason. Also, resonance waves XW ₃ , XW ₅ , XW ₇ ... Formed by exciting the medium (air) in the vicinity of the open ends 31 and 32 of the open tube 30 by standing waves SW ₃ , SW ₅ , SW ₇ . The side of the open ends 31 and 32 becomes a node ND. Therefore, the inventors speculated that odd-numbered standing waves SW ₃ , SW ₅ , SW ₇ ... After the third order are also attenuated for the same reason as the standing wave SW ₁ .

Next, paying attention to the relationship between the secondary standing wave SW ₂ in the space S and the behavior of the medium (air) in the open tube 30, the medium (near the open ends 31 and 32 in the open tube 30 ( Air) is vibrated by a change in the sound pressure of the antinode LP _2-1 of the standing wave SW ₂ , and traveling waves TW ₂ and TW ₂ ′ having the same phase and opposite traveling directions are generated. When the traveling wave TW ₂ and TW ₂ 'are combined in an open tube 30, the resonance wave XW ₂ having the same wavelength lambda ₂ and the standing wave SW ₂ occurs. As shown in FIG. 14 (B), the middle between the open end 31 and 32 in the resonance wave XW ₂ becomes belly LP. Since the tube length of the open tube 30 is the same as the wavelength λ ₂ of the standing wave XW ₂ , if the middle between the open ends 31 and 32 becomes an antinode LP, the open ends 31 and 32 side also becomes an antinode LP. For this reason, the sound pressure distribution of the standing wave SW ₂ is not relaxed at the positions of the opening ends 31 and 32. The inventors speculated that the attenuation of the standing wave SW ₂ does not occur due to the above reason. Also, resonance waves XW ₄ , XW ₆ , XW ₈ ... Formed by exciting the medium (air) in the vicinity of the open ends 31 and 32 of the open tube 30 by standing waves SW ₄ , SW ₆ , SW ₈ . The sides of the open ends 31 and 32 become the abdomen LP. Therefore, the inventors speculated that the fourth and subsequent even-order standing waves SW ₄ , SW ₆ , SW ₈ ... Do not attenuate for the same reason as the standing wave SW ₂ .

<Third Embodiment>
FIG. 15 is a front view of a speaker 9D according to the third embodiment of the present invention. The speaker 9D includes a cabinet 1 ′, a speaker unit 2 ′ fixed to the outside of the cabinet 1 ′, and an open tube 40 ′ housed in a space S ′ in the cabinet 1 ′. The cabinet 1 'is a hollow rectangular parallelepiped surrounded by wall surfaces 4U' and 4D 'opposed in the vertical direction, wall surfaces 4F' and 4B 'opposed in the front-rear direction, and wall surfaces 4L' and 4R 'opposed in the left-right direction. It has a shape. The left-right width W ′ (the distance between the wall surfaces 4L ′ and 4R ′: for example, W ′ = 430 mm) in the space S ′ in the cabinet 1 ′ is the depth width L ′ (the distance between the wall surfaces 4F ′ and 4B ′: For example, L ′ = 200 mm). Further, the vertical width H ′ (the distance between the wall surfaces 4U ′ and 4D ′: for example, H ′ = 1050 mm) in the space S ′ is larger than the left-right width W ′.

The speaker unit 2 ′ of the speaker 9D is fixed to the approximate center of the wall surface 4F ′ of the cabinet 1 ′ (the position of the node ND _1-1 of the primary standing wave SW ₁ generated in the space S ′). Open tube 40 of the speaker 9D 'is the space S' forms a straight line with a generally semi-wavelength of the pipe length of the secondary standing wave SW ₂ that occurs in. The open tube 40 ′ is fixed on the wall surface 4F ′ in the space S ′ in a posture inclined with respect to the facing direction of the two facing surfaces of the wall surfaces 4U ′ and 4D ′. The open end 41 ′ of the open tube 40 ′ is disposed at the position of the approximate node ND _2-1 of the standing wave SW ₂ , and the open end 42 ′ is the position of the approximately antinode LP _2-2 of the standing wave SW _2. Is arranged. According to the speaker 9D, it is possible to suppress the standing wave SW _k that is generated in the facing direction of the wall surfaces 4U ′ and 4D ′. Moreover, in this speaker 9D, since the open tube 40 ′ is straight, the processing of the open tube 40 ′ can be performed more easily than in the case of the speakers 9 to 9C.

  Here, the inventors performed the following verification in order to confirm the effect of this embodiment. The inventors input the test sound signal ST to the speaker unit 2 ′ for the speaker 9D shown in FIG. 15, and the sound wave radiated from the speaker unit 2 ′ is measured at the measurement point P (more specifically, in the space S ′. Is the frequency response R which is the difference between the spectrum of the input signal ST and the measurement signal SM when measured at the measurement point P (see FIG. 15) near the inside of the position where the wall surfaces 4D ′, 4B ′ and 4R ′ intersect. -9D was calculated by simulation. Similarly, for the speaker 9D ′ obtained by removing the open tube 40 ′ from the speaker 9D, the test sound signal ST is input to the speaker unit 2 ′, and the sound wave radiated from the speaker unit 2 ′ is measured at the measurement point P. The frequency response R-9D ′, which is the difference in spectrum between the input signal ST and the measurement signal SM, was calculated by simulation. FIG. 16 shows the frequency responses R-9D and R-9D 'with the frequency axes aligned.

Referring to FIG. 16, in both frequency responses R-9D and R-9D ′, a peak appears in the vicinity of 300 Hz. However, in the frequency response R-9D ′, the peak amplitude near 300 Hz is smaller than that in the frequency response R-9D. In the frequency response R-9D, the peak near 300 Hz is broken. Therefore, it was confirmed that can suppress the second-order standing wave SW ₂ in the 'space S by' speaker 9D.

<Fourth embodiment>
FIG. 17 is a front view of a speaker 9E according to the fourth embodiment of the present invention. This speaker 9E is obtained by covering both open ends of the open tube 20 in the speaker 9A shown in FIG. 2 with a breathable sound absorbing material (for example, a nonwoven fabric). In addition, in the example of FIG. 17, although both the open ends of the open tube 20 are all covered with the air permeable sound-absorbing material, you may cover only a part of open ends with the air permeable sound-absorbing material. As is well known, the breathable sound-absorbing material has the property of causing peaks and dips in the frequency response of the space separated from the outside. Therefore, according to this embodiment, the secondary inhibiting amount of a standing wave SW ₂ can be made larger than the first embodiment.

Here, the inventors performed the following verification in order to confirm the effect of this embodiment. The inventors defined a speaker 9E _{BS in} which both open ends of the open tube OP in the speaker 9A _BS used in the verification of the first embodiment were covered with a breathable sound absorbing material. On top of that, this speaker _{9E BS,} which is the difference between the spectrum of the measurement signal SM of the speaker units _SU measuring points P-1 and the input signal ST of the _{CNT, P-2, P-} 3 frequency response _R 1 _{-9E BS,} R ₂ -9E _BS, was calculated _R 3 _{-9E BS.} Figure 18 is a frequency response _R 1 _{-9a BS} used in verification of the frequency response _R 1 _{-9E BS} in the first embodiment '(FIG. 8) shows align the frequency axis. FIG. 19 shows the frequency response R ₂ -9E _BS and the frequency response R ₂ -9A _BS ′ (FIG. 9) used in the verification of the first embodiment, with the frequency axes aligned. Figure 20 is a frequency response _R 3 _{-9a BS} used in verification of the frequency response _R 3 _{-9E BS} in the first embodiment '(FIG. 10) shows align the frequency axis.

18, 19, referring to FIG. 20, the frequency response _{R 1 -9A BS ', R 2} -9A BS', the R 3 _{-9A BS} ', whereas steep peak is generated in the vicinity of 300Hz , frequency response _{R 1 -9E BS, R 2 -9E} BS, the R 3 _{-9E BS,} the amplitude in the vicinity of 300Hz is made substantially flat. From this, it was confirmed that the amount of suppression of the secondary standing wave SW ₂ is larger in the speaker 9E _BS than in the bass reflex type speaker 9A _BS shown in FIG.

  As mentioned above, although embodiment of this invention was described, various other embodiment can be considered to this invention. For example, it is as follows.

(1) The open tubes 10 and 20 in the space S of the speakers 9 and 9A in the first embodiment may be replaced with those having a shape different from the J-shape. For example, like the speaker 9F shown in FIG. 21, the open tube 20 of the speaker 9A in the example of FIG. 2 may be replaced with an open tube 20 ″ having a spiral shape. In this case, a standing wave in the space S may be used. place a "open end 21 of the" open tube 20 to the position of Ryakuhara LP of SW _2, it may be arranged to open end 22 'to a position of substantially clause ND standing wave SW _2. Also with this configuration, the same effect as the first embodiment can be obtained. Further, the open tube 10 and the open tube 20 may be formed in a zigzag shape (for example, W shape, N shape, Z shape, S shape, etc.). Further, the speaker 9, 9A, 9B, 9C, 9E is shaped so that a part of the bent portion of the open tube 10, 20, 30, 40 in the cabinet 1 protrudes outside the cabinet 1, and the open tube 10 , 20, 30, 40 may be used as a handle for gripping the speakers 9, 9A, 9B, 9C, 9E.

(2) In the first to fourth embodiments, the present invention is applied to the suppression of the standing wave SW _k in the space in the cabinet of the speakers 9, 9A, 9B, 9C, 9E. However, the present invention is applied to the suppression of standing waves of other types of acoustic equipment having a housing (acoustic room) that encloses a space surrounded by at least a pair of opposing surfaces, a transport aircraft, a house, etc. Also good. For example, the present invention may be applied to suppression of standing waves in a space in an acoustic piano, electronic piano, or guitar housing. Further, the present invention may be applied to suppression of standing waves in a space in a car, a train, an airplane, a motorcycle, a water bike, a ship, and a rocket. Further, the present invention may be applied to suppression of standing waves in a space surrounded by walls such as a soundproof room, a classroom, and a performance room.

(3) In the third embodiment, the open tube 40 'is fixed on the wall surface 4F' in the space S 'in a posture inclined with respect to the facing direction between the wall surfaces 4U' and 4D '. However, the open tube 40 'may be fixed on the wall surface 4B' in the space S 'in a posture inclined with respect to the facing direction between the wall surfaces 4U' and 4D '. Further, the open tube 40 ′ only needs to be accommodated in the space S ′ in a posture inclined with respect to the facing direction between the wall surfaces 4 </ b> U ′ and 4 </ b> D ′, and need not be fixed to the wall surface 4 </ b> F ′ or the wall surface 4 </ b> B ′. For example, the opening end 41 ′ of the open tube 40 ′ may be disposed in the vicinity of the intersection position of the wall surfaces 4F ′ and 4L ′, and the opening end 42 ′ may be disposed in the vicinity of the intersection position of the wall surfaces 4B ′ and 4R ′. . On the contrary, the open end 42 'of the open tube 40' is arranged in the vicinity of the intersection position of the wall surfaces 4F 'and 4L', and the opening end 41 'is in the vicinity of the intersection position of the wall surfaces 4B' and 4R '. You may arrange in.

(4) In the third embodiment, the open tube 40 'is linear. However, the open tube 40 'may be bent into a J shape, a U shape, or other shapes.

(5) In the fourth embodiment, both open ends of the open tube 20 in the speaker 9A are covered with a breathable sound absorbing material. However, one open end of the open tube 20 may be covered with a breathable sound absorbing material. Further, one or both of the open ends of the open tube 10 of the speaker 9 shown in FIGS. 1A and 1B may be covered with a breathable sound absorbing material. Further, one or both of the open ends of the open tube 30 of the speaker 9B shown in FIGS. 11 (A) and 11 (B) may be covered with a breathable sound absorbing material. Further, one or both open ends of the open tube 40 ′ of the speaker 9 </ b> D shown in FIG. 15 may be covered with a breathable sound absorbing material.

(6) In the said 4th Embodiment, both the opening ends of the open tube 20 were covered with the nonwoven fabric which is one of the air permeable sound-absorbing materials. However, open-celled porous materials such as urethane foam and foamed resin, glass wool, aluminum foam metal, metal fiber board, wood pieces and fragments thereof, wood fibers, pulp fibers, MPP (Microperforated Panel), cow wool felt, anti-hair A member having a structure that can be regarded as a porous material such as felt, wool, cotton, nonwoven fabric, cloth, synthetic fiber, wood powder molding material, and paper molding material may be used instead of the nonwoven fabric.

(7) The open tubes 10 and 30 in the first to fourth embodiments have tube lengths of approximately half the wavelength of the primary standing wave SW ₁ . However, if the primary is not necessary for the suppression of the standing wave SW ₁ may be a length of approximately half wavelength of a standing wave SW _k of the secondary and subsequent tube length of open tube 10 and 30. Similarly, the tube lengths of the open tubes 20 and 40 ′ may be approximately half the wavelength of the standing wave SW _k after the third order.

(8) In the first, second, and fourth embodiments, a plurality of types of open tubes 10, 20, and 30 having different tube lengths may be stored in the space S in the cabinet 1. In the third embodiment, a plurality of types of open tubes 40 ′ having different tube lengths may be stored in the space S ′ in the cabinet 1 ′. In the third embodiment, a plurality of types of standing waves SW _k generated in the facing direction of the wall surfaces 4U ′ and 4D ′, the facing direction of the wall surfaces 4F ′ and 4B ′, and the facing direction of the wall surfaces 4L ′ and 4R ′. to the suppress standing wave SW _k, it may be achieved 'cabinet 1' a plurality of types of open tube 40 having different directions of inclination in the space S 'in.

(9) The first, second, and fourth embodiments has been to a standing wave SW _k wall 4U and 4D direction in the space S in the cabinet 1 and suppression target. However, the standing tubes in the wall surfaces 4F and 4B direction and the standing waves in the wall surfaces 4L and 4R directions are suppressed, and the open tubes that play a role in suppressing these standing waves are replaced with the open tubes 10, 20, and 30. Or, it may be stored in the space S together with the open tubes 10, 20, 30.

(10) A feature of the present invention is that a standing wave that cannot coexist with an identified standing wave is generated as a means for reducing a standing wave generated in a space surrounded by a pair of facing surfaces of a casing. An open tube is provided in the housing. FIGS. 22A to 22F are diagrams schematically and comprehensively showing the relationship between the standing wave generated in the space in the housing and the open tube in the acoustic device according to the present invention. In these drawings, the open tube L2 provided in the housing of the acoustic device, the first open end N1 and the second open end N2 of the open tube L2, and the first in the facing direction of the pair of facing surfaces in the housing are shown. A length L1 from one opening end N1 to a second opening end N2 is shown.

  The example shown in FIG. 22A is the aspect disclosed in the first embodiment (FIG. 1). The example shown in FIG. 22B is the aspect disclosed in the third embodiment (FIG. 11). As a modification of the mode shown in FIG. 22 (b), the mode shown in FIG. 22 (c) and the mode shown in FIG. 22 (d) are conceivable. Also in these aspects, since the open tube generates a standing wave that cannot coexist with the standing wave generated between the wall surfaces 4U and 4D, the standing wave generated between the wall surfaces 4U and 4D is reduced.

  In this case, the shape of the open tube may be any, and may be outside the cabinet 1 as shown in FIG. Moreover, as shown in FIG.22 (f), the open tube has come out of the cabinet 1, and may be the string winding shape.

DESCRIPTION OF SYMBOLS 1 ... Cabinet, 2 ... Speaker unit, 4U, 4D, 4F, 4B, 4L, 4R ... Wall surface, 9, 9A, 9B, 9C, 9D, 9E ... Speaker, 10, 20, 30, 40 ... Open tube, 11, 12, 31, 32, 41, 42 ... open ends.

Claims (9)

An acoustic device that includes a housing that includes at least a space surrounded by a pair of opposing surfaces, and that reduces standing waves generated between the pair of opposing surfaces,
A sound source installed in the housing and emitting sound toward the outside of the housing;
An open tube having first and second open ends located within the space;
With
The acoustic device, wherein the open tube has a tube length that is approximately twice the distance between the first opening end and the second opening end in a direction from one of the pair of opposed surfaces to the other. .   The acoustic device according to claim 1, further comprising: a sound source that is installed in the casing and is installed on the casing other than the pair of opposed surfaces.   The acoustic apparatus according to claim 1, further comprising a sound source that is installed in the housing and has a sound emitting surface parallel to an opening direction of the open tube.   The acoustic device according to any one of claims 1 to 3, wherein the first opening end is located in the vicinity of one of the opposing surfaces of the pair of opposing surfaces. 5. The acoustic device according to claim 1, wherein the second opening end is positioned at a substantially center between the pair of opposed surfaces. The acoustic device according to claim 1, wherein the open tube has a tube length substantially equal to a distance between the pair of opposed surfaces. The acoustic device according to any one of claims 1 to 6, wherein the open tube has a bent shape or a spiral shape. An acoustic device that includes a housing that includes at least a space surrounded by a pair of opposing surfaces, and that reduces standing waves generated between the pair of opposing surfaces,
Comprising an open tube having first and second open ends located within the space;
The acoustic device, wherein the open tube has a tube length that is approximately twice the distance between the first opening end and the second opening end in a direction from one of the pair of opposed surfaces to the other. . The acoustic device according to claim 1, wherein the acoustic device is a speaker device.

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