JP2940418B2 - Inner ear headphones - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner earphone having improved frequency characteristics in a low frequency range. 2. Description of the Related Art The low-frequency reproduction limit of conventional open-air headphones is mainly determined by the compliance C _md (reciprocal of stiffness S) of the vibration system and the equivalent mass M _{d of the} vibration system, and is shown in FIG. As described above, the response in the low-frequency range where the frequency is equal to or less than f ₀ is reduced. This f
₀ is approximately: In order to lower f ₀ , the compliance C _md (cm / dyne) of the vibration system must be increased or the equivalent mass M
_d (gr) needs to be heavier. However, there is a limit to increase the compliance C _md, also when heavier equivalent mass M _d of the vibration system, so leading to deterioration of the acoustic characteristics in reducing or treble sensitivity, the heavier the equivalent mass M _d Have their own limits. Also, as is well known, the low-tone range resonance frequency f ₀ tends to increase as the diameter of the headphone becomes smaller, so that the inner ear-type headphones (ie, earphones) having a small diameter originally reproduce the low-tone range. There was a drawback that the sound was difficult to hear. For example, in the conventional earphone shown in FIG. 2, a magnetic circuit is formed from a cylindrical magnet 1, a cylindrical yoke 2 and a plate 3 sandwiching the magnet 1 from both sides, and a magnetic circuit is formed in a magnetic gap 4 thereof. A diaphragm 6 coupled to the inserted voice coil 5 is assembled on the front surface to form a driver unit 7 as an acoustic converter, and an outer peripheral portion of the driver unit 7 is attached to a housing 8. The through hole 9 at the center of the driver unit 7 is filled with a sound absorbing material 10, the braking layer 12 is provided on the back of the through hole 11, and several through holes 13 are provided in the housing 8, so that Is controlled. [0004] Therefore, the above configuration is shown in Fig. 3 by an acoustic equivalent circuit. Here, M _d , C _md and R _d are the equivalent mass, compliance and acoustic resistance of the vibration system, V _s is the signal source, _Ra is the acoustic resistance by the sound absorbing material 10 and the damping layer 12, R _b and C _b constituting the circuit are the acoustic resistance due to the through hole 13 of the housing 8 and the compliance due to the rear space (that is, the back cavity) of the housing 8. In FIG. 3, M _cup , C _cup, and R _cup surrounded by a symbol G are equivalent mass, compliance, and acoustic resistance formed by the ear holes when the earphone is inserted into the ear holes, respectively. [0006] However, the acoustic resistance R _b according to the through hole 13 of the housing 8 is negligibly small compared to the R _a, and since C _b can almost negligible, these R _b and C constituting the parallel circuit
_b has little effect, and the acoustic equivalent circuit in FIG.
_d, the series resonant circuit of C _md, R _d and R _a. Therefore, as described above, the bass resonance frequency f ₀ is approximately given by: Not lower given, and as shown in FIG. 1, R _a
Is small, the characteristic has a peak near f ₀ , and only the sound in the vicinity is emphasized to produce a sound that resounds. On the other hand, you come to decrease characteristic from a frequency higher than R _a is as large as f _0, bass reproduction is not sufficient. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a conventional driver unit (that is, an acoustic transducer) without changing its structure. By changing the acoustic equivalent circuit on the back side of the converter, the response in the low range is improved, in other words, providing an earbud type headphone that can obtain a large-diameter class low range response with a small diameter. Is to do. A first embodiment of an inner earphone (ie, earphone) according to the present invention will be described below with reference to the drawings. As shown in FIG. 4, the earphone according to the first embodiment of the present invention has the same sound as that shown in FIG.
Since a converter (that is, a driver unit) 7 is used, the same parts as those described above are denoted by the same reference numerals and description thereof will be omitted. In the first embodiment, the through-hole 11 on the back surface of the driver unit 7 and the through-hole 9 at the center of the driver unit 7 are provided with a damping material (that is, a sound absorbing material such as a cloth such as nylon mesh or urethane having a resistance component almost equal to zero). Material) may be provided. The housing 20 is formed in a shape constricted rearward in a conical shape except for a portion related to the lead wire 21, and has an upper duct 22 and a lower duct directed upward and downward, respectively, at its rear end. 23 are formed. That is, the upper and lower ducts 22 and 23 project from the housing 20 to the outside and in directions different from each other. The upper duct 22 has an opening 24, and the lower duct 23 has a flexible joint 25.
Is inserted, and the lead wire 21 is
Are introduced into the housing 20. In addition, the externally protruding lengths of these ducts 22 and 23 are set to be sufficiently larger than their inner diameters (that is, the diameters of the openings 24). Further, as is apparent from FIG. 4, the duct 23 forms a lower duct portion in cooperation with the joint 25,
The duct 22 alone forms an upper duct portion. Also, as is apparent from FIG.
Section is longer than the upper duct section,
The upper and lower duct portions have different lengths from each other. A plurality of through holes 26 are formed on the side surface of the housing 20, and a braking plate 27 made of urethane or the like is provided on the inner surface of each of the through holes 26. Therefore, FIG.
In the conventional earphone shown in FIG.
The acoustic resistance Rb due to the through holes 13 of FIG.
Negligibly small compared to the acoustic resistance Ra of the layer 12
However, in the earphone according to the present invention shown in FIG.
The acoustic resistance Rb in the through hole 26 of the body 20 is
6 is provided with a braking plate 27 on the inner surface thereof.
Than the acoustic resistance Rb in the conventional earphone shown in FIG.
Of course it gets bigger. In addition, at the front of the housing 20, various types of gently curved disk-shaped protection plates that cover the front surface of the driver unit 7 are attached. That is, these protection plates are made of a punched metal having a mesh with a relatively large hole diameter sequentially from the inside, and mechanically protect the driver unit 7 from external pressure or the like.
8, a protection plate 29 for dust prevention made of a base cloth on the outside thereof and a protection plate 30 for ear holes made of perforated metal having a small hole diameter mesh. Further, the housing 20 is
As is apparent from FIG.
The space is divided into a front space and a rear space, and
It is configured to be able to be attached to the ear hole from the front side of
You. Therefore, the housing 20 was attached to the ear hole from the front side.
In the state, the housing 20 closes the ear hole and the acoustic transducer 7 is closed.
Sound emitted from the front of the
Sound from the rear surface of the acoustic transducer 7
And the upper duct part 22 and the lower duct parts 23 and 25
It is released to the outside of the ear hole through each,
The sound emitted from the rear surface of the transducer 7 is transmitted to the rear space and the braking material 2.
7 through the through-holes 26 provided outside the ear holes.
Can be released. FIG. 5 shows an acoustic equivalent circuit of the earphone according to the first embodiment of the present invention configured as described above. Here, M _d , C _md and R _d relate to the vibration system of the driver unit 7 as in the case of FIG. _Ra is the acoustic resistance due to the through hole 11 and the central through hole 9 of the driver unit 7, and is approximately _Ra =
0. The C _b compliance by the back cavity for forming the housing 20 in a conical shape, the R _b acoustic resistance by the braking plate 27, L _d and R _'d is the upper duct
R ′ _d is considerably small due to the inductance (equivalent mass) and acoustic resistance due to the gate section 22 and the lower duct sections 23 and 25 . Therefore, in this earphone, the upper equivalent weight M _d of the vibration system duct 22 and the lower duct section 23,
Is added equivalent mass L _d of 25, also the upper duct section 22
And also acoustic resistance R _'d of the lower duct section 23 and 25 have been added. For this reason, the braking on the back side of the earphone is L
_d / R _'d, performed by the parallel resonant circuit of the C _b and R _b, so that the parallel resonant circuit is applied to the series resonant circuit of the M _d, C _md and R _d. [0013] Since is as described above, bass resonance frequency of the entire acoustic equivalent circuit of the earphone, as shown in FIG. 6, the inductance (equivalent mass) L _d min,
The frequency is lowered to f ' ₀ lower than the bass resonance frequency f ₀ of the driver unit 7 itself, and thus the sound range, particularly the bass range, can be expanded. Further, as shown in FIG. 6, reducing the resistance component R _b entering parallel to L _d f _'0 is increased,
On the other hand, when _Rb is increased, the midrange falls. Therefore L _d
In order to broaden the range and flatten from the low range to the high range, to enhance the high range with the range expanded, or to obtain a desired frequency characteristic by appropriately selecting _Rb Can be. As for the high frequency range, when _Rb is increased, the level of the high frequency range necessary for the audibility in the reproduction of the earphone is improved. Furthermore, in this earphone, since the ducts 22 and 23 project outside from the housing 20, the size of the housing 20 is small and the shape thereof is limited in the case of the earphone. The length and thickness of the ducts 22 and 23 can be selected almost without being restricted by the size and shape of the housing 20. On the other hand, ducts 22 and 23
If a long a thick ones, short inductance L _d as compared to a slender and does not change substantially, but the acoustic resistance R _'d
Becomes smaller. Therefore, by arbitrarily setting the length and thickness of the ducts 22 and 23, the above-mentioned frequency characteristics can be made more desirable. It is to be noted that acoustic control can be performed by making the length 1 (ell) of the duct 22 and / or the brake plate 27 in FIG. 4 variable. FIG. 7 shows the sound pressure-frequency characteristic A of the conventional earphone shown in FIG. 2 and the same driver unit 7 as that of the conventional earphone.
FIG. 9 shows a comparison with a sound pressure-frequency characteristic B in an earphone according to the present invention provided with a duct of 20 mm.
As is apparent from FIG. 7, f ₀ is 1 from 220 Hz.
It can be seen that the frequency has dropped to 50 Hz. Also around 2kHz
It can also be seen that the level of the side drops to some extent, and the level in the high range around 4 kHz, which is necessary for reproducing the headphones, rises. In addition, as shown in FIG.
Parts (ie, upper duct part 22 and lower duct part 2)
3, 25), these two ducts
Resonance with its equivalent mass and acoustic resistance almost identical to each other
Unless the frequencies are almost identical to each other,
And the level around 2kHz
Is further reduced. 2 and 4, the driver unit 7 has a diameter of φ16. FIG. 8 shows a second embodiment of the present invention in which dust is taken into consideration by making the shape of the duct 31 inverted U-shaped and the opening 32 is directed downward, and the length of the duct 31 is made as long as desired. 14 shows an earphone according to the third embodiment, and is otherwise the same as that described in the first embodiment. Then, even if the shape of the duct 31 in an inverted U-shape, because the duct 31 it is clear that exerts effects as the inductance (equivalent mass) L _d, as a whole, this second embodiment The earphone according to the embodiment can exhibit the same operation and effect as the earphone according to the first embodiment. [0018] [Effect of the Invention] According to the present invention configured as described above, a plurality of duct portion is the sound through the side space after out of the plane housing after the acoustic transducer is introduced, the duct It protrudes to the outside larger than the inside diameter of the part . Therefore, these multiple
Since the inductance component can be given to the acoustic equivalent circuit of the inner ear headphones by the duct portion of the above, the bass resonance frequency of the acoustic equivalent circuit of the whole headphone is lower than the bass resonance frequency of the acoustic transducer itself due to the inductance component. Reduced to value. Also , simply providing a plurality of ducts in the housing by integral molding etc. can effectively improve the response in the low frequency range, so the manufacturing process is extremely large although the response in the low frequency range can be effectively improved. It is simple and therefore, even in the case of the inner-ear type headphones using the conventional acoustic transducer, it is possible to obtain a rich reproduced sound in a low frequency range unlike the conventional one, and as a result, the low frequency range is described. If
Even with a small diameter, a response of a large diameter can be obtained, which is extremely advantageous. Also each other of and a plurality of duct portion to the outside from the housing
In different directions.
One of these ducts is an acoustic transducer
Sound from the back of the bowl through the back space
And these ducts are connected to the headphone
To add an inductance component to the acoustic equivalent circuit of the
Protruding outside the inner diameter of the duct part
You. Therefore, in the case of inner ear type headphone shape a small size of the housing is subject to limitation, this field
The case where multiple ducts are provided inside the housing.
In addition, it is possible to arbitrarily set the length and thickness of the plurality of duct portions without being substantially restricted by the size and shape of the housing. For this purpose, the size of the housing itself is increased.
Since the inductance component and the acoustic resistance component of the plurality of duct portions can be selected to desired values without any problem, a desired sound pressure-frequency characteristic can be obtained by appropriately selecting these values.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sound pressure characteristic diagram of a conventional open air type headphone. FIG. 2 is a central longitudinal sectional view of a conventional earphone. FIG. 3 is an acoustic equivalent circuit diagram of the conventional earphone shown in FIG. 2; 4A is a central longitudinal sectional view of an earphone according to a first embodiment of the present invention, and FIG. 4B is an external perspective view of the earphone shown in FIG. 4A. 5 is an acoustic equivalent circuit diagram of the earphone shown in FIG. 6 is a sound pressure characteristic diagram of the earphone shown in FIG. 7 is a sound pressure-frequency characteristic comparison diagram between the conventional earphone shown in FIG. 2 and the earphone shown in FIG. 4 according to the first embodiment of the present invention. FIG. 8 is an external perspective view of an earphone according to a second embodiment of the present invention. [Description of Signs] 1 magnet 2 yoke 3 plate 4 magnetic gap 5 voice coil 6 diaphragm 7 driver unit (acoustic transducer) 20 housing 22 duct 23 duct 26 through hole 27 braking plate 31 duct

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-76994 (JP, A) JP-A-58-6492 (JP, U) JP-A-53-15326 (JP, U) JP-A-53- 35524 (JP, U) (58) Field surveyed (Int.Cl. ⁶ , DB name) H04R 1 / 10,1 / 02

Claims (1)

(57) [Claims] 1. An acoustic transducer and a housing to which the acoustic transducer is attached
Body andWith The housing is provided by the acoustic transducerThe above housingInterior space
Is divided into a front space and a rear space,the above
HousingIt is configured so that it can be attached to the ear hole from the front side of From the housing to the outside and in different directions
Protrude respectivelyMultipleDuct sectionHowever, these multiple duct sections
Is connected to the space on the rear side of the housing.
LikeIn the above housingProvided, Rear of the above acoustic transducerFromSoundAre the above multiple ducts
From one of the duct sectionsThrough the above rear side space
When configured so that it can be released outside the ear hole,
ToThe plurality of ducts are Inductors in the acoustic equivalent circuit
Add a sense componentfor,Than the inner diameter of the above duct
bigOutsideProtruding intoCharacterized by the inner
Earphones.2. The multiple ducts above must be different in length
The inner ear according to claim 1, which is provided on the housing.
Type headphones.