JPH07170589A - Inner ear head phone - Google Patents

Abstract

PURPOSE:To easily reproduce sound sufficiently in low frequency sound range even when the conventional acoustic transducer is used. CONSTITUTION:The device consists of an acoustic transducer 7 and a box 20 where the transducer 7 is installed. Duct parts 22 and 23 which are selected to the length longer than the inner diameter so as to give the inductance component to the acoustic equivalent circuit are projected outside from the box 20 so as to emit the sound from the back side of the transducer 7 on the box 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner ear type headphone having improved frequency characteristics in the low frequency range.

[Background Art and Problems] The bass reproduction limit of conventional open-air headphones is mainly determined by the compliance C _md (reciprocal of stayness 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 was low in the bass range where the frequency was f ₀ or lower. This f
₀ is almost

[Equation 1] And to reduce f ₀ , increase the compliance C _md (cm / dyne) of the vibration system or equivalent mass M
_d (gr) needs to be heavy. However, there is a limit to increase the compliance C _md , and if the equivalent mass M _d of the vibration system is increased, the sensitivity is lowered and the acoustic characteristics in the high frequency range are deteriorated. Therefore, the equivalent mass M _d is increased. Also has its own limits.

As is well known, since the bass resonance frequency f ₀ tends to be larger in a smaller-diameter headphone, an inner ear type headphone (that is, an earphone) which originally has a smaller diameter reproduces a bass 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 and a cylindrical yoke 2 and a plate 3 which sandwich the magnet 1 from both sides, and a magnetic circuit is formed in the magnetic gap 4. The vibrating plate 6 coupled to the inserted voice coil 5 is incorporated in the front surface to form a driver unit 7 as an acoustic transducer, and the outer peripheral portion of the driver unit 7 is attached to the housing 8. Then, the through hole 9 in the center of the driver unit 7 is filled with the sound absorbing material 10, the damping layer 12 is provided on the back surface of the through hole 11, and some through holes 13 are provided in the housing 8 to obtain the frequency characteristic. Are controlling.

Therefore, the acoustic equivalent circuit of the above configuration is as shown in FIG. Here, M _d , C _md, and R _d are the equivalent mass of the vibration system, the compliance, and the acoustic resistance, respectively, V _s is the signal source, and _Ra is the acoustic resistance of the sound absorbing material 10 and the damping layer 12, which are parallel to each other. R _b and C _b forming 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 reference symbol G are equivalent mass, compliance and acoustic resistance formed by the ear hole when the earphone is inserted into the ear hole.

However, since the acoustic resistance R _b due to the through hole 13 of the housing 8 is so small as to be negligible as compared with R _a, and C _b is almost negligible, these R _b and C forming a parallel circuit are connected.
The effect of _b is small, and the acoustic equivalent circuit in FIG.
It becomes a series resonance circuit of _d , C _md , R _d and R _a . Therefore, as described above, the bass resonance frequency f ₀ is almost

[Equation 2] Given that R _a is not low, and as shown in FIG.
When is small, a peak is generated in the characteristic near f ₀ , and only the sound in the vicinity is emphasized and becomes a resonating sound. On the other hand, when R _a is large, the characteristics deteriorate from a frequency higher than f ₀ , and the reproduction of bass is not sufficient.

[0007]

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 driver unit (that is, an acoustic transducer) which has been conventionally used without changing the structure thereof. It is to improve the response in the low range by changing the acoustic equivalent circuit on the back side, in other words, to provide inner ear type headphones that can obtain the low range response of a large diameter class with a small diameter. is there.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of an inner ear type headphone (that is, an earphone) according to the present invention will be described below with reference to the drawings.

As shown in FIG. 4, since the earphone according to the first embodiment of the present invention uses the same sound converter (ie, driver unit) 7 shown in FIG. 2, The same parts as those described above are designated by the same reference numerals and the description thereof will be omitted. In the first embodiment, the rear through hole 11 and the central through hole 9 of the driver 7 include a cloth such as nylon mesh having a resistance component substantially equal to zero, a braking material such as urethane (that is, a sound absorbing material). )
Etc. may be provided.

The housing 20 is formed into a conical shape that is constricted rearward except for the portion related to the lead wire 21, and the rear end portion thereof has an upper duct 22 and a lower duct which are directed upward and downward, respectively. The duct 23 is formed. The upper duct 22 has an opening 24, a flexible joint 25 is fitted in the lower duct 23, and the lead wire 21 is introduced into the housing 20 via the joint 25. The lengths of the ducts 22 and 23 are set sufficiently larger than their inner diameters (that is, the diameters of the openings 24).

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 side surfaces of these through holes 26. Further, on the front portion of the housing 20, various gently curved disc-shaped protective plates that cover the front surface of the driver unit 7 are attached. That is, these protective plates are
A protective plate 28 made of punching metal having a mesh with a relatively large hole diameter and mechanically protecting the driver unit 7 from external pressure, etc., a dustproof protective plate 29 made of a base cloth on the outside thereof, and a mesh having a small hole diameter. The ear protection plate 30 is made of punching metal.

FIG. 5 shows an acoustic equivalent circuit of the earphone according to the first embodiment of the present invention constructed as described above. Here, M _d , C _md and R _d respectively relate to the vibration system of the driver unit 7 as in the case of FIG. R _a is the acoustic resistance due to the through hole 11 of the driver unit 7 and the through hole 9 in the center, and R _a =
It is 0. Further, C _b is the compliance due to the back cavity for forming the housing 20 in a conical shape, R _b is the acoustic resistance due to the braking plate 27, and L _d and R ′ _d are the duct 2
2,23 in by inductance (equivalent mass) and acoustic resistance, R _'d is variable become smaller. Therefore, in the case of this earphone, the equivalent mass L _d of the ducts 22 and 23 is added to the equivalent mass M _d of the vibration system, and the acoustic resistance R ′ _{d of the} ducts 22 and 23 is also added. For this reason, braking on the back side of the earphone is performed by a parallel resonant circuit of L _d / R ′ _d , C _b and R _b , and this parallel resonant circuit is the above M _d , C.
It will be added to the series resonant circuit of _md and R _d .

As described above, the bass resonance frequency of the entire acoustic equivalent circuit of this earphone is represented by the inductance (equivalent mass) L _{d as} shown in FIG.
The bass resonance frequency f ₀ of the driver unit 7 itself is lowered to f ′ _0, which makes it possible to widen the tone range, particularly the bass range. Further, as shown in FIG. 6, when the resistance component R _b entering in parallel with L _d is reduced, f ′ ₀ rises,
On the other hand, when R _b is increased, the mid range falls. Therefore L _d
On the other hand, by appropriately selecting R _b , widening the range and flattening from the low range to the high range, enhancing the high range with the range expanded, or obtaining a desired frequency characteristic. You can With respect to the high frequency range, increasing R _b improves the level of the high frequency range which is necessary for hearing when reproducing the earphone.

Furthermore, in this earphone, since the ducts 22 and 23 are projected from the housing 20 to the outside, in the case of the earphone, the size of the housing 20 is small and its shape is restricted. The length and thickness of the ducts 22 and 23 can be selected without being restricted by the size and shape of the housing 20. On the other hand, the ducts 22 and 23
If the length is long and thick, the inductance L _d is substantially unchanged as compared with the short and thin one, but the acoustic resistance R ′ _d.
Becomes smaller. Therefore, by setting the length and thickness of the ducts 22 and 23 as desired, the frequency characteristics can be made more desirable.

Note that, for example, the acoustic control can be performed by making the length l of the duct 22 and / or the braking 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 used in the duct 22 shown in FIG.
6 shows a comparison with sound pressure-frequency characteristics B in an earphone according to the present invention provided with a duct of × 20 mm.
As apparent from FIG. 7, f ₀ is 220 Hz to 1
It can be seen that the frequency has dropped to 50 Hz. It can also be seen that the level in the high range around 4 kHz, which is necessary for reproducing headphones, increases. 2 and 4, the driver unit 7 has a diameter of 16 mm.

In the second embodiment of the present invention shown in FIG. 8, the duct 31 is shaped like an inverted U so that the opening 32 faces downward to prevent dust and the length of the duct 31 is lengthened as desired. 2 shows an earphone according to the embodiment of the present invention, and is otherwise the same as that described in the first embodiment. And, even if the shape of the duct 31 is inverted U, it is clear that the duct 31 exerts the function and effect as the inductance (equivalent mass) L _d . Therefore, as a whole, the second embodiment The earphone in FIG. 9 can also exert the same effect as the earphone in the first embodiment.

[0018]

As described above, according to the present invention,
Since the duct part can add an inductance component to the acoustic equivalent circuit of the inner ear type headphones,
The bass resonance frequency of the acoustic equivalent circuit as a whole is lowered to a value lower than the bass resonance frequency of the acoustic transducer itself by the inductance component. In addition, the response in the low frequency range can be effectively improved by simply providing the duct part in the housing by integrally molding, etc., but the manufacturing process is extremely simple despite the fact that the response in the low frequency range can be effectively improved. Therefore, even with inner-ear headphones that use a conventional acoustic transducer, unlike the conventional ones, it is possible to obtain a reproduced sound with a rich bass range. Even with the caliber, a large caliber response is obtained, which is extremely advantageous. Also, since the duct part protrudes from the housing to the outside, in the case of inner ear type headphones, the size of the housing is small and its shape is limited, but it is almost restricted by the size and shape of this housing. It is possible to arbitrarily set the length and thickness of the duct portion without being cut. Therefore, the inductance component and the acoustic resistance component due to the duct portion can be selected to desired values, respectively, and a desired sound pressure-frequency characteristic can be obtained by appropriately selecting these values.

[Brief description of 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.

3 is an acoustic equivalent circuit diagram of the conventional earphone shown in FIG.

4A is a central longitudinal sectional view of the earphone according to the 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.

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.

[Explanation of symbols]

 1 Magnet 2 Yoke 3 Plate 4 Magnetic Gap 5 Voice Coil 6 Vibration Plate 7 Driver Unit (Acoustic Transducer) 20 Housing 22 Duct 23 Duct 26 Through Hole 27 Braking Plate 31 Duct

Claims (1)

[Claims] 1. A duct section comprising an acoustic transducer and a housing to which the acoustic transducer is attached, the duct section having a length larger than an inner diameter in order to impart an inductance component to an acoustic equivalent circuit of the acoustic transducer. An inner ear type headphone, characterized in that it is provided in the housing by projecting to the outside so that sound emitted from the rear surface of the acoustic transducer can be emitted to the outside.