Acoustic device

Abstract

The invention provides an acoustic device which is arranged on a seat and can apply sound pressure emphasized in a low-frequency band to the ears of a listener seated on the seat. In an acoustic device (10), a housing (11) and a speaker unit (20) are fixed inside a seat back (2), and an opening (12b) of a duct (12) extending from the housing (11) faces an ear (E) of a listener (6). The resonance frequency (Fd) of the Helmholtz resonator formed by the housing (11) and the duct (12) is set to a frequency band higher than the resonance frequency (F0) of the vibration system mass including the mass of the vibration part of the speaker unit (20) and the load mass of the air in the duct (12). A listening position is set at a position where a linear distance (Ld) from an opening (12b) of the duct (12) is closer than a linear distance (Ls) from a diaphragm of the speaker unit (20).

Description

Technical Field

[0001] The present invention relates to an audio device capable of providing a sound pressure with an emphasized low frequency range to a listener sitting on a seat provided in a vehicle interior or the like. Background Art

[0002] In Patent Document 1 Figure 3 An audio device arranged on a seat is shown in FIG. The audio device includes an audio housing having an upper acoustic cavity and a lower acoustic cavity. An electroacoustic transducer as a speaker unit is arranged at the junction of the upper acoustic cavity and the lower acoustic cavity. One radiating surface of the electroacoustic transducer is acoustically coupled with the upper acoustic cavity, and the other radiating surface is acoustically coupled with the lower acoustic cavity. The upper chamber outlet opens near the head of a person sitting on the seat. The lower chamber outlet opens downward toward the floor, and the lower chamber outlet is located significantly away from the person's head.

[0003] In paragraph

[0017] of Patent Document 1, it is stated that the head of a person sitting on a chair is significantly closer to the upper chamber outlet than the lower chamber outlet, and therefore the sound heard by the person sitting on the chair is affected by the radiation from the upper chamber outlet much more than the lower chamber outlet. In addition, in paragraph

[0011] , it is stated that the pressure wave provided from the electroacoustic transducer to the upper chamber is opposite in phase to the pressure wave provided to the lower chamber. In paragraph

[0017] , at a position (50) relatively equidistant from the lower chamber outlet and the upper chamber outlet, the sound energy from the two outlets interferes with each other due to the phase difference, and therefore has a smaller amplitude than near the head of the person sitting on the chair.

[0004] [Prior art literature]

[0005] [Patent Document]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2007-82220 Summary of the invention

[0007] Patent Document 1 states that the upper chamber outlet is located near the human head and that acoustic energy is imparted to the human head from the outlet, but it does not specify what kind of resonance action is performed by the upper acoustic cavity. The resonance frequency of a general Helmholtz resonator having a housing and a pipe is inversely proportional to the pipe length of the pipe and proportional to the opening cross-sectional area of ​​the pipe, but the pipe length of the upper chamber outlet described in Patent Document 1 is approximately zero, so it can be easily predicted that low-frequency resonance cannot be generated by the upper acoustic cavity.

[0008] The present invention solves the above-mentioned technical problems of the prior art, and its object is to provide an audio device that allows a person sitting in a seat in a vehicle, etc. to hear a relatively wide-band bass sound with a sufficiently large sound pressure, and can attenuate the sound pressure of the bass range at a position away from the seat.

[0009] The acoustic device of the present invention comprises: a housing; a duct communicating with the internal space of the housing; and a speaker unit for imparting sound pressures of opposite phases to the inside of the housing and to the outside of the housing, wherein the acoustic device is characterized in that:

[0010] At least the housing and the speaker unit are fixed to the seat,

[0011] The resonance frequency Fd of the Helmholtz resonator formed by the housing and the duct is set to a frequency band higher than the resonance frequency F0 of the mass of the vibration system including the mass of the vibration part of the speaker unit and the load mass of the air in the duct.

[0012] A listening position is set at a position where a straight-line distance Ld from the opening of the duct is closer than a straight-line distance Ls from the diaphragm of the speaker unit.

[0013] In the audio device of the present invention, the speaker unit and the housing are preferably accommodated in a seat back or a seat cushion.

[0014] A sound pressure having a phase opposite to that of the sound pressure applied to the interior of the housing is directed from the speaker unit toward a listener seated on a seat, and the opening of the duct opens near an ear of the seated person.

[0015] The audio device of the present invention may be configured such that the duct is a flexible hose and at least a portion of the duct is accommodated in the seat back.

[0016] In the acoustic device of the present invention, it is preferred that the resonance frequency F0 of the vibration system mass is less than 100 Hz.

[0017] In the acoustic device of the present invention, the sound pressure obtained from the opening of the duct has a peak located in a frequency band lower than 100 Hz and a peak located in a frequency band higher than 100 Hz.

[0018] [Effects of the invention]

[0019] The resonance frequency Fd of the Helmholtz resonator composed of a shell and a pipe connected to the internal space of the shell is physically calculated by the internal volume V of the shell and the pipe length L and cross-sectional area S of the pipe {Fd = (C / 2·π)√(S / V·L); C is the speed of sound}. The resonance frequency Fd is inversely proportional to the internal volume V of the shell and the pipe length L of the pipe, and is proportional to the cross-sectional area S of the pipe. In the operation of the Helmholtz resonator, when the frequency of the pressure wave input into the shell coincides with the resonance frequency Fd, the air in the shell expands and contracts like a spring, and the air in the pipe resonates in a phase opposite to the input pressure wave. If the input pressure wave is higher than the above resonance frequency Fd, the air in the shell expands and contracts like a spring, but the air in the pipe is difficult to move. When the input pressure wave is lower than the above resonance frequency Fd, the air in the pipe moves by the amount of expansion and contraction of the air in the shell, and the air in the pipe moves in the pipe in the same phase as the input pressure wave.

[0020] The sound device of the present invention uses a bass reflex structure in which a speaker unit is mounted on a housing, and in a frequency band lower than the resonance frequency Fd of the Helmholtz resonator, a vibration system mass Mms including the mass of the vibration part of the speaker unit and the load mass of the air in the duct moving at the same period as the vibration part can resonate (resonate). That is, the resonance frequency F0 calculated by taking into account the spring coefficient of the spring support system Kms of the elastic modulus of the air in the housing from the vibration-damping component and the edge component of the speaker unit and is set to a frequency band lower than the resonance frequency Fd of the Helmholtz resonator. In this specification, the resonance frequency F0 at this time is referred to as "the resonance frequency F0 of the vibration system mass Mms of the speaker system in the bass reflex structure". In the present invention, for example, by increasing the mass of the vibration part of the speaker unit 20, reducing the inner diameter of the duct 12 and extending the duct length, increasing the load mass of the air in the duct, etc., the vibration system mass Mms is designed to be heavier, and the spring coefficient of the spring support system Kms of the speaker system 20 is designed to be lower, thereby adjusting the resonance frequency F0 of the vibration system mass Mms to a frequency band lower than the resonance frequency Fd of the Helmholtz resonator.

[0021] The audio device of the present invention, in a bass reflex structure, sets the resonance frequency Fd of the Helmholtz resonator to a frequency band higher than the resonance frequency F0 of the vibration system mass Mms including the vibration part of the speaker unit and the load mass of the air in the duct. Thus, when focusing on the sound pressure radiated from the opening of the duct, the level of the sound pressure can be increased in a wider frequency band from near the resonance frequency F0 to near the resonance frequency Fd, and can operate as a so-called bandpass audio device.

[0022] In the audio device of the present invention, at least the housing and the speaker unit are fixed to the seat, and the listening position is set at a position where the straight-line distance Ld from the opening of the duct is closer than the straight-line distance Ls from the vibration plate of the speaker unit. Therefore, the sound pressure is directly applied to the ears of the seated person from the opening of the duct, and the seated person can preferentially hear the sound of the bass range emphasized in the frequency band from near F0 to near Fd. However, when the speaker unit operates to generate a wide-band sound pressure from near the resonance frequency F0 to near the resonance frequency Fd, the vibration part of the speaker and the air in the duct operate in phase, so the sound pressure released from the duct to the external space and the sound pressure applied from the vibration plate of the speaker unit to the external space of the housing (the space opposite to the internal space of the housing) become opposite phases. Therefore, at a position far from the opening of the duct, the sound pressures of opposite phases interfere with each other to cancel each other out, and the sound of the bass from near the resonance frequency F0 to near the resonance frequency Fd can be suppressed. For example, when an audio device is installed on a seat in a vehicle cabin, the sound of the frequency band can be emphatically heard by the ears of the seat occupant, but the bass sound from near the resonance frequency F0 to near the resonance frequency Fd is difficult to leak into the cabin away from the opening of the duct and then outside the vehicle.

[0023] In order to effectively listen to the sound pressure of the bass range through human ears, the sound pressure of the bass range needs to be increased. On the contrary, the sound pressure of the bass range is easily transmitted to the surroundings, for example, the outer panels of the vehicle are also easily transmitted. The audio device of the present invention can provide the bass range to the ears of the listener with emphasis in a relatively wide frequency band, and on the other hand, the sound pressure of the bass range can be reduced at a position far away from the audio device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a side view showing the first embodiment of the present invention in which the audio device is mounted in a seat back of a seat in a vehicle.

[0025] Figure 2 yes Figure 1 An enlarged cross-sectional view of the audio device shown.

[0026] Figure 3 This is a side view showing a second embodiment of the present invention in which an audio device is mounted in a seat cushion of a seat in a vehicle.

[0027] Figure 4 This is a graph showing the frequency characteristics of the sound pressure received near the opening of the duct in Example 1 of the acoustic device of the present invention.

[0028] Figure 5 This is a graph showing the frequency characteristics of the sound pressure received near the opening of the duct in Example 2 of the acoustic device of the present invention.

[0029] Figure 6This is a graph showing the frequency characteristics of the sound pressure received near the opening of the duct in Example 3 of the acoustic device of the present invention.

[0030] Figure 7 This is a graph showing the frequency characteristics of the sound pressure received near the opening of the duct in Example 4 of the acoustic device of the present invention.

[0031] Figure 8 This is a graph showing the frequency characteristics of the sound pressure received near the opening of the duct in the audio device of the comparative example. DETAILED DESCRIPTION

[0032] In the audio device of the present invention, at least the housing and the speaker unit are fixed to the seat, and preferably they are embedded in the interior of the seat. Figure 1 The first embodiment shown in the figure is fixed to the inside of the seat back, or as Figure 3 The housing and the speaker unit may be fixed inside the seat cushion as in the second embodiment shown in FIG. Alternatively, the housing and the speaker unit may be configured to be small and fixed inside the headrest. The seat may be provided in the interior of a car, or in a vehicle other than a car, such as inside a train. Alternatively, the seat may be provided in a theater, a game center, etc., or may be used at home.

[0033] Figure 1 and Figure 2 FIG. 1 shows an audio device 10 according to a first embodiment of the present invention. The audio device 10 is for vehicle use. Figure 1 and Figure 2 In the figure, the X1-X2 direction is the front-to-back direction, the X1 direction is the front direction, i.e. the direction of the vehicle's travel, and the X2 direction is the rear direction. The Y1-Y2 direction is the up-down direction, the Y1 direction is the top direction, and the Y2 direction is the bottom direction.

[0034] exist Figure 1 1 shows a seat 1 as a driver's seat in a vehicle and a steering wheel 5 located in front of the seat 1 (in the X1 direction). The seat 1 has a seat back 2, a seat cushion 3, and a headrest 4. A listener 6 sitting on the seat 1 is a driver and has a torso 7 and a head 8. The head 8 is located in front of the headrest 4, and the left and right ears E of the head 8 are listening positions.

[0035] like Figure 2 As shown, the audio device 10 has a housing 11, a duct 12, and a speaker unit 20, forming a so-called bass reflex speaker system. The housing 11 has a mounting hole (baffle opening) 11a with a surface opening facing forward (X1 direction) and a connection port 11b with a surface opening facing upward (Y1 direction). The housing 11 is a sealed box with no openings except for the mounting hole 11a and the connection port 11b. The speaker unit 20 is mounted in the mounting hole 11a. Figure 1As shown, the housing 11 and the speaker unit 20 are fixed inside the seat back 2. One end of the duct 12 is a connection end 12a, which is connected to the connection port 11b of the housing 11, and the internal space of the duct 12 is connected to the internal space of the housing 11. The other end of the duct 12 is an opening 12b. The opening 12b functions as a sound outlet for releasing sound pressure to the outside. Figure 1 As shown, the opening portion 12 b of the duct 12 is located at the upper portion of the seat back 2 , and opens toward the ear E in the vicinity of the ear E of the listener 6 .

[0036] The position of the ears E of the audio device 10 when the head 8 of an adult of standard body size sitting on the seat 1 contacts the headrest 4 is the listening position. Two ducts 12 are connected to the housing 11, and the openings 12b of the two ducts 12 are opened at positions close to the left and right ears E of the listener 6. Alternatively, two sets of audio devices 10 connected to one duct 12 may be provided in the housing 11 having the speaker unit 20, and each audio device 10 is provided inside the seat back 2, and the openings 12b of the ducts 12 of each audio device 10 are opened at positions close to the left and right ears E, respectively. At least a part of the duct 12 is provided inside the seat back 2, but in order to facilitate the arrangement and drawing of the duct 12 inside the seat back 2, the duct 12 is preferably formed of a flexible hose. The cross section of the duct 12 is circular, oblong, rectangular, etc., and the cross-sectional area is constant over the entire length of the duct.

[0037] Figure 2 The center line Os of the speaker unit 20 is shown in the figure. The speaker unit 20 is fixed to the mounting hole 11a of the housing 11 with the center line Os slightly tilted in the clockwise direction relative to the front-rear direction (X1-X2 direction) with the frame 21. On the frame 21, a magnetic circuit portion 22 is fixed on one side along the center line Os, and a conical vibration plate 23 is provided on the other side along the center line Os. The bobbin extends from the center of the vibration plate 23 to the left side of the figure along the center line Os, and the voice coil is wound on the bobbin, and the voice coil is located in the magnetic gap of the magnetic circuit portion 22. The hole formed in the connection portion between the vibration plate 23 and the bobbin is covered by a cover member on the right side of the figure. The vibration plate 23, the bobbin, the voice coil, the cover member, etc. constitute the vibration portion of the speaker unit 20. The outer periphery of the vibration plate is supported on the frame 21 by an edge member, and the bobbin is supported on the frame by a buffer member. The edge member and the vibration-damping member function as a part of a spring support system that supports the vibration portion so that it can vibrate freely along the center line Os. A portion of the mass of the spring support system is added as the mass of the vibration part.

[0038] The speaker unit 20 utilizes the electromagnetic force excited by the sound current supplied to the voice coil and the transverse magnetic flux supplied to the voice coil from the magnetic circuit portion 22 to make the vibration portion including the vibration plate 23 vibrate linearly along the center line Os in the frame 21. The vibration of the vibration plate 23 imparts an inner sound pressure (inner pressure wave) Pi to the inner space of the housing 11, and imparts an outer sound pressure (external pressure wave) Po to the outer space of the housing 11. The air density periods of the inner sound pressure Pi and the outer sound pressure Po differ by 180 degrees and are in opposite phases to each other. Figure 1 As shown, the position of the ear E when the listener 6 is seated and the head 8 is in contact with the headrest 4 is the listening position, and the straight line distance Ld from the listening position to the opening center of the opening portion 12b of the duct 12 is shorter than the straight line distance Ls from the listening position to the center of gravity of the vibration plate 23 of the speaker unit 20. The straight line distance Ls is preferably more than twice the straight line distance Ld, and more preferably more than three times. The straight line distance Ld is about 100 mm to 200 mm, for example, 150 mm.

[0039] Next, the operation of the audio device 10 will be described.

[0040] Figure 1 and Figure 2 The acoustic device 10 shown is composed of a housing 11 and a pipe 12, which constitute a Helmholtz resonator. Without considering the operation of the speaker unit 20, the Helmholtz resonator has a predetermined resonance frequency Fd. The resonance frequency Fd is physically calculated from the internal volume V of the housing and the pipe length L and cross-sectional area S of the pipe, and is obtained by the formula Fd = (C / 2·π)√(S / V·L); (C is the speed of sound). The resonance frequency Fd is inversely proportional to the internal volume V of the housing and the pipe length L of the pipe, and is proportional to the cross-sectional area S of the pipe.

[0041] When the speaker unit 20 is operated, the inner sound pressure Pi generated by the operation of the vibration plate 23 becomes an input pressure wave to the Helmholtz resonator. When the frequency of the input pressure wave is consistent with the resonance frequency Fd or is close to it, the air in the duct 12 resonates, and the sound pressure radiated from the opening 12b of the duct 12 becomes higher. At this time, the vibration of the inner sound pressure Pi given by the vibration plate 23 and the vibration of the air in the duct 12 are in opposite phases to each other, and the sound pressure radiated from the opening 12b of the duct 12 to the outside is in phase with the outer sound pressure Po radiated from the speaker unit 20 to the outside of the housing 11. In the frequency band where the frequency of the inner sound pressure Pi is higher than the resonance frequency Fd, as the frequency of the inner sound pressure Pi becomes higher, the sound pressure radiated from the opening 12b of the duct 12 decreases. This is because, in the frequency band where the frequency of the input pressure wave to the Helmholtz resonator is higher than the resonance frequency Fd, even if the air inside the housing 11 expands and contracts, it is difficult for the air in the duct 12 to follow, and the air in the duct 12 is difficult to move.

[0042] If the frequency of the inner sound pressure Pi input to the housing 11 becomes a frequency band lower than the resonance frequency Fd of the Helmholtz resonator, the spring function of the air inside the housing 11 is reduced, and the pressure change of the air inside the housing 11 is directly transmitted to the inside of the duct 12, and the air in the duct 12 vibrates in the same phase as the vibration plate 23 of the speaker unit 20. When the sound pressure radiated from the opening 12b of the duct 12 vibrates in the same phase as the inner sound pressure Pi, the outer sound pressure Po radiated from the speaker unit 20 to the outside of the housing 11 and the sound pressure radiated from the opening 12b of the duct 12 are in opposite phases. In the conventional bass reflex speaker system using the Helmholtz resonator, since the position far from both the opening 12b of the duct 12 and the speaker unit 20 becomes the listening position, there is a problem that the sound pressure from the opening 12b and the outer sound pressure Po in opposite phases cancel each other, and the lower the operating frequency of the vibration plate 23 of the speaker unit 20, the more the audible sound pressure is attenuated.

[0043] However, if Figure 1 As shown, if a position closer to the straight-line distance Ld from the opening 12b of the duct 12 than the straight-line distance Ls from the speaker unit 20 is set as the listening position, even when the speaker unit 20 operates at a frequency lower than the resonance frequency Fd, the listener 6 is hardly affected by the interference of the external sound pressure Po emitted from the speaker unit 20, and can directly listen to the sound pressure from the opening 12b. Therefore, the audio device 10 of the embodiment sets the resonance frequency F0 of the vibration system mass Mms of the speaker system in the bass reflex structure to a frequency band lower than the resonance frequency Fd of the Helmholtz resonator, and increases the amplitude of the air in the duct 12 in the frequency band where the vibration plate 23 of the speaker unit 20 and the air in the duct 12 vibrate in phase, thereby amplifying the sound pressure acting on the ear E from the opening 12b of the duct 12.

[0044] Figures 4 to 7The frequency characteristics of the sound pressure obtained from the opening 12b of the duct 12 in each embodiment of the present invention are shown. As shown in each figure, if the resonance frequency F0 of the speaker system in the bass reflex structure is set to a frequency band lower than the resonance frequency Fd of the Helmholtz resonator, the sound pressure acting on the ear E from the opening 12b of the duct 12 can be amplified in the frequency band from the vicinity of the resonance frequency F0 to the vicinity of the resonance frequency Fd. When the resonance frequency F0 of the vibration system mass Mms is set to a bass region of less than 100 Hz, the reproduced sound with the bass region emphasized can be heard through the ear E of the listener 6. In addition, when the resonance frequency F0 of the vibration system mass Mms is set to a frequency band lower than 100 Hz and the resonance frequency Fd of the Helmholtz resonator is set to a frequency band higher than 100 Hz, the sound pressure applied to the ear E from the opening 12b of the duct 12 has a peak located in the frequency band lower than 100 Hz and near the resonance frequency F0 and a peak located in the frequency band higher than 100 Hz and near the resonance frequency Fd, and functions as a band-pass acoustic device in which the frequency band from the vicinity of the resonance frequency F0 to the vicinity of the resonance frequency Fd is emphasized. As shown in each embodiment, when the straight-line distance Ld from the opening 12b of the duct 12 to the ear E is set to 150 mm, the following characteristics are obtained: the sound pressure difference in the frequency band from the peak near the resonance frequency F0 to the peak near the resonance frequency Fd is 10 dB or less, the sound pressure decreases as the frequency is lower than the peak near the resonance frequency F0, and the sound pressure decreases as the frequency is higher than the peak near the resonance frequency Fd.

[0045] The sound pressure acting on the ear E from the opening 12b of the duct 12 becomes higher between the peak near the resonance frequency F0 and the peak near the resonance frequency Fd, but the sound pressure from the opening 12b and the outer sound pressure Po from the speaker unit 20 are in opposite phases. Therefore, at a position far away from both the opening 12b and the speaker unit 20, the sound pressures of opposite phases interfere and are canceled, and the sound pressure being listened to is greatly reduced. Therefore, it is difficult for the sound in the bass range to be transmitted to a position far away from the seat 1 where the listener 6 is seated. In particular, the sound pressure in the bass range from the peak near the resonance frequency F0 to the peak near the resonance frequency Fd is easy to propagate to the surroundings. For example, when the seat 1 is in the interior of a car, the bass is easy to propagate to the outside of the car body, but as described above, the sound pressures of opposite phases interfere and are canceled, thereby easily preventing sound leakage to the outside of the car body.

[0046] In the above-mentioned audio device 10, relatively low-frequency sound pressure is emphatically applied to the ear of the listener 6 from the opening 12b of the duct 12, but the audio device 10 may also generate sound pressure in the middle range. In addition, in the audio device 10, other speaker units that mainly generate sound pressure in the low range and further generate sounds from the middle range to the high range are installed in the seat 1 or around the listener 6.

[0047] Figure 3FIG. 1 shows an acoustic device 110 according to a second embodiment of the present invention. Figure 2 The audio device 10 shown in the figure also has a Helmholtz resonator composed of a housing 11 and a duct 12 connected to the housing 11, and a speaker unit 20 is fixed to the housing 11. The housing 11 and the speaker unit 20 are fixed inside the seat cushion 3. The duct 12 is composed of a flexible hose, and a part of it passes through the inside of the seat cushion 3 and the inside of the seat back 2. In addition, the opening 12b of the duct 12 is located at the upper part of the seat back 2 and opens at a position close to the ear E of the listener 6. In the audio device 110 of the second embodiment, since the speaker unit 20 is provided inside the seat cushion 3, it is possible to ensure that the straight-line distance Ls from the center of gravity of the vibration plate 23 of the speaker unit 20 to the ear E in the listening position is long, and the straight-line distance Ls can be set to be 4 times or more and 5 times or more of the straight-line distance Ld from the opening 12b of the duct 12 to the ear E. By increasing the difference between the straight-line distances Ls and Ld, it is possible to listen to the sound emitted from the opening 12 b of the duct 12 without being significantly disturbed by the external sound pressure Po of the speaker system.

[0048] exist Figure 1 In the audio device 10 of the first embodiment shown in FIG. 1 , the outer sound pressure Po from the speaker unit 20 is directed toward the body of the listener 6. Figure 3 In the audio device 110 of the second embodiment shown, the outer sound pressure Po from the speaker unit 20 is directed toward the buttocks of the listener 6. In the audio devices 10 and 110, by setting the resonance frequency F0 of the vibration system mass Mms to a frequency band less than 100 Hz, the bass is emphatically provided from the opening 12b of the duct 12 toward the ear E, but the outer sound pressure Po of the same period as the bass is provided to the body of the listener 6 as vibration, and the listener 6 can feel the bass with the whole body.

[0049] [Example]

[0050] Figures 4 to 7 10 and 110 are examples of the acoustic devices 10 and 110 of the present invention. Figure 8 The examples and comparative examples are simulation results of the frequency characteristics of the sound pressure when a 1W sine wave is input to the voice coil of the speaker unit 20 and the sound pressure Po from the outside of the speaker unit 20 is ignored, assuming that the sound pressure is measured at a position 150 mm away from the opening 12b of the duct 12. The horizontal axis represents the frequency (Hz) and the vertical axis represents the sound pressure level (dB).

[0051] <Example 1>

[0052] Figure 4 The frequency characteristics in Example 1 are shown. The parameters of Example 1 are as follows.

[0053] Internal volume of housing 11: 150cc

[0054] Length of pipeline 12: 50cm

[0055] Inner diameter of pipe 12 (inner diameter): 2 cm

[0056] Effective vibration diameter of the vibration plate 23: 6.2 cm

[0057] The resonance frequency of the Helmholtz resonator Fd: 110Hz

[0058] Resonance frequency of vibration system mass F0: 48Hz

[0059] <Example 2>

[0060] Figure 5 The frequency characteristics in Example 2 are shown. The parameters of Example 2 are as follows.

[0061] Internal volume of housing 11: 300cc

[0062] Length of pipeline 12: 50cm

[0063] Inner diameter of pipe 12 (inner diameter): 3 cm

[0064] Effective vibration diameter of the vibration plate 23: 6.2 cm

[0065] The resonance frequency of the Helmholtz resonator Fd: 107Hz

[0066] Resonance frequency of vibration system mass F0: 68Hz

[0067] <Example 3>

[0068] Figure 6 The frequency characteristics in Example 3 are shown. The parameters of Example 3 are as follows.

[0069] Internal volume of housing 11: 300cc

[0070] Length of pipeline 12: 50 cm

[0071] Inner diameter of pipe 12 (inner diameter): 3 cm

[0072] Effective vibration diameter of vibration plate 23: 8 cm

[0073] The resonance frequency of the Helmholtz resonator Fd: 112Hz

[0074] Resonance frequency of vibration system mass F0: 48Hz

[0075] <Example 4>

[0076] Figure 7 The frequency characteristics in Example 4 are shown. The parameters of Example 4 are as follows.

[0077] Internal volume of housing 11: 200cc

[0078] Length of pipeline 12: 30cm

[0079] Inner diameter of pipe 12 (inner diameter): 3 cm

[0080] Effective vibration diameter of the vibration plate 23: 8 cm

[0081] The resonance frequency of the Helmholtz resonator Fd: 118Hz

[0082] Resonance frequency of vibration system mass F0: 70Hz

[0083] <Comparative Example>

[0084] Figure 8 The frequency characteristics in the comparative example are shown. The comparative example is a simulation result showing the frequency characteristics of the sound pressure level near the opening of the duct in a general bass reflex speaker system. The resonance frequency Fd of the Helmholtz resonator is set to around 70 Hz, and the resonance frequency F0 of the vibration system mass is set to a frequency band higher than the resonance frequency Fd.

[0085] like Figure 8 As in the comparative example of , in the conventional bass reflex speaker system, by setting the resonance frequency Fd of the Helmholtz resonator to a frequency band lower than the resonance frequency F0 of the speaker system, the sound pressure can be increased near the resonance frequency Fd. However, the increase in sound pressure is limited to a narrow frequency band near the resonance frequency Fd. In contrast, in Examples 1 to 4, the sound pressure acting on the ear E from the opening 12b of the duct 12 can be increased in a wider frequency band from the resonance frequency F0 of the vibration system mass of the speaker system to the resonance frequency Fd of the Helmholtz resonator, and the wide-band bass can be listened to with emphasis.

[0086] according to Figures 4 to 7 In the embodiment shown, in order to increase the load mass of the air in the duct 12, the resonance frequency F0 of the vibration system mass of the speaker system can be set to a frequency band lower than the resonance frequency Fd of the Helmholtz resonator. Therefore, it is preferred that the length of the duct be more than 8 times the inner diameter (inner diameter) of the duct 12, and more preferably more than 10 times.

[0087] [Explanation of Reference Numerals]

[0088] 1 Seat

[0089] 2 Seat back

[0090] 3 Seat cushions

[0091] 4 Headrest

[0092] 10,110 sound installation

[0093] 11. Housing

[0094] 12 Pipeline

[0095] 12b Opening

[0096] 20 Speaker Units

[0097] 22 Magnetic circuit part

[0098] 23 Vibration Plate

[0099] E ear (listening position)

Claims

1. An audio device comprising: shell; a pipe communicating with the inner space of the housing; as well as a speaker unit that applies sound pressures of opposite phases to the inside of the housing and to the outside of the housing, The audio device is characterized in that At least the housing and the speaker unit are fixed to the seat, The resonance frequency (Fd) of the Helmholtz resonator formed by the housing and the duct is set to a frequency band higher than the resonance frequency (F0) of the mass of the vibration system including the mass of the vibration part of the speaker unit and the load mass of the air in the duct, A listening position is set at a position where a straight-line distance (Ld) from the opening of the duct is closer than a straight-line distance (Ls) from the diaphragm of the speaker unit.

2. The audio device according to claim 1, wherein: The speaker unit and the housing are stored in a seat back or a seat cushion. A sound pressure having a phase opposite to that of the sound pressure applied to the interior of the housing is directed from the speaker unit toward a listener seated on a seat, and the opening of the duct opens near an ear of the seated person.

3. The audio device according to claim 2, wherein: The duct is a flexible hose, at least a portion of which is received in the seat back.

4. The audio device according to any one of claims 1 to 3, wherein: The resonance frequency (F0) of the vibration system mass is less than 100 Hz.

5. The audio device according to claim 4, wherein: The sound pressure obtained from the opening of the duct has a peak in a frequency band lower than 100 Hz and a peak in a frequency band higher than 100 Hz.

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