JPH07170591A - Headphone - Google Patents

Abstract

PURPOSE:To reproduce sound rich in bass very easily different from the case of conventional headphones even if a conventional acoustic transducer is used. CONSTITUTION:The device consists of an acoustic transducer 7 and a box 20 where the transducer 7 is attached. The box 20 has a duct part 18 which emits the sound from the back side of the transducer 7. The duct 18 has a variable means which adjusts the inductance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a headphone having improved frequency characteristics in a low tone range, and is particularly suitable for application to a small diameter inner ear type headphone.

[0002]

[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 low frequency range where the frequency was f ₀ or less. This f ₀
Is almost

[Equation 1] In order to lower f ₀ , the compliance C _md (cm / dyne) of the vibration system should be increased or the equivalent mass M _d (g
r) needs to be heavy. But compliance C
There is a limit to _{raising md} , and the equivalent mass M of the vibration system
_{If d} is made heavy, the sensitivity is lowered and the acoustic characteristics in the high range are deteriorated. Therefore, there is a limit to making the equivalent mass M _d heavy.

As is well known, since the bass resonance frequency f ₀ tends to be larger in a headphone having a smaller diameter, it is difficult to hear a reproduced sound in a bass range in a headphone having a small diameter (that is, an earphone). There was a flaw.

For example, in the conventional earphone shown in FIG. 2, a magnetic circuit is formed by a cylindrical magnet 1, and a cylindrical yoke 2 and a plate 3 sandwiching the magnet 1 from both sides, and a magnetic circuit is formed in the magnetic gap 4. The vibration 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. The sound absorbing material 10 is filled in the central through hole 9 of the driver unit 7, the braking layer 12 is provided on the back surface of the through hole 11, and the through hole 13 is provided in the housing 8 to control the frequency characteristic. There is.

Therefore, the above-mentioned configuration is shown in FIG. 3 as 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, and _Ra is the acoustic resistance of the sound absorbing material 10 and the damping layer 12, which are parallel to each other. R configuring the circuit
_b and C _b are the acoustic resistance due to the through hole 13 of the housing 8, and
It is 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 of the coupler 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 can be almost neglected, these R _b and C which form a parallel circuit.
_b effect of less acoustic circuit in FIG 3 is substantially M _d,
It becomes a series resonant circuit of C _md , R _d and R _a . Therefore, as described above, the bass resonance frequency f ₀ is approximately

[Equation 2] 1 and does not lower, and as shown in FIG. 1, when R _a is small, a peak appears 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, f ₀
The characteristics are deteriorated from the higher frequency, and the bass is not sufficiently reproduced.

[0008]

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 rear surface of an acoustic transducer without changing the structure of a conventionally used driver unit (that is, an acoustic transducer). It is to improve the response in the low frequency range by changing the acoustic equivalent circuit on the side, in other words, to provide a headphone capable of obtaining a low frequency response of a large diameter class with a small diameter.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to inner ear type headphones (that is, earphones) will be described below with reference to the drawings.

As shown in FIG. 4, the earphone according to the embodiment of the present invention uses the same acoustic transducer (that is, driver unit) 7 shown in FIG. The same parts are designated by the same reference numerals and the description thereof is omitted. In this embodiment, the rear through hole 11 and the central through hole 9 of the driver unit 7 are provided with a cloth such as nylon mesh having a resistance component substantially equal to zero, or a braking layer (that is, a sound absorbing material) such as urethane. Good.

The casing 20 is formed into a conical shape squeezed rearward except for the portion related to the lead wire 21, and has a duct-shaped tubular portion 22 at the rear end thereof which is directed upward and downward, respectively. , 23 are formed. The upper tubular portion 22 has an opening 24, and a flexible joint 25 is fitted in the lower tubular portion 23. The lead wire 21 is connected to the housing 20 via the joint 25. Has been introduced within.

A plurality of through holes 26 are formed on the side surface of the housing 20.
A braking plate 27 made of urethane or the like is provided on the inner side surface of the through hole 26. And housing 2
At the front part of 0, 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, in order from the inside, a vibration-proof protective plate 28 made of punching metal having a mesh with a relatively large hole diameter, and a dust-proof protective plate 2 made of a base cloth on the outside thereof.
9 and a protective plate 30 for an ear hole made of a punching metal having a mesh with a small hole diameter.

In the present invention, the length of the duct portion provided in the housing 20 is variable in order to emit the sound emitted from the rear surface of the driver unit 7, which is an acoustic transducer, to the outside. For this reason, the above-described earphone includes an outer cylinder 19 that forms the duct portion 18 of the housing 20 together with the duct-shaped cylindrical portion 22, and the outer cylinder 19 is a tubular shape that is formed integrally with the housing 20. It is adapted to slide vertically with respect to the portion 22.

FIG. 5 shows an acoustic equivalent circuit of the earphone according to the 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 FIG.
_Ra is the acoustic resistance due to the through hole 11 of the driver unit 7 and the through hole 9 in the center, and is approximately _Ra ≈ 0. Further, C _b is compliance due to a back cavity based on the case 20 having a conical shape, R _b is acoustic resistance due to the braking plate 27, and L _d and R ′ _d are inductances (equivalent mass) due to the tubular portions 22 and 23. And acoustic resistance, _R'd is very small. Therefore, the braking on the back is L _d , C _b and R _b.
Parallel resonant circuit of M _d , C _md and R _d
Will be added to the series resonance circuit of. Therefore, as shown in FIG. 6, the bass resonance frequency of the entire acoustic equivalent circuit of the earphone is the bass resonance frequency f of the driver unit 7 itself due to the inductance (equivalent mass) L _d.
It is lowered to f ′ ₀ which is lower than ₀ . Similarly, as shown in FIG. 6, when the resistance component R _b that enters in parallel with L _d is made smaller, f ′ ₀ rises, while when R _b is made larger, the middle range falls. Therefore, it is necessary to select R _b appropriately for L _d . With respect to the high frequency range, increasing R _b improves the level of the high frequency range that is necessary for headphone reproduction in terms of hearing.

As can be seen from the above results, in FIG. 4, when the outer cylinder 19 is moved up and down with respect to the tubular portion 22 as necessary to change the length l (ell) of the duct portion 18, A preferable acoustic control can be performed.

FIG. 7 shows a sound pressure-frequency characteristic A in the conventional earphone shown in FIG. 2, and the same driver unit is used, and a duct portion 18 of φ3 × 20 mm as shown in FIG. 4 is provided. 6 shows a comparison with sound pressure-frequency characteristic B in the earphone according to the present invention. This Figure 7
As is clearer, f ₀ is 220Hz to 150Hz
You can see that it has fallen to. It can also be seen that the level in the high range around 4 kHz, which is necessary for headphone reproduction, rises. 2 and 4, the driver unit has a diameter of 16 mm. Further, in the earphone according to the present invention, it is possible to control the sound pressure-frequency characteristic by changing the length of the duct portion 18. For example, the length l (el) of the duct portion 18 is shown in FIG. If it is made longer than the state shown, the sound pressure-frequency characteristic can be changed within the range from B to C in FIG. 7.

[0017]

Since the present invention has the above-mentioned structure,
The inductance component due to the duct portion provided in the housing for emitting the sound emitted from the rear surface of the acoustic transducer to the outside is added to the acoustic equivalent circuit of the acoustic transducer, and for this reason, the acoustic equivalent circuit of the headphones according to the present invention is added. The bass resonance frequency as a whole is lowered to a value lower than the bass resonance frequency of the acoustic transducer itself due to the inductance component. Therefore, according to the present invention, the response in the bass range is improved,
Therefore, even with headphones using acoustic transducers of the same size, unlike the conventional headphones, it is possible to obtain reproduced sound with a rich bass range. Speaking of the low frequency range, it is extremely advantageous that a response of a large diameter class can be obtained even with a small diameter.

Further, according to the present invention, since the duct portion provided in the housing for emitting the sound emitted from the rear surface of the acoustic transducer to the outside is provided with the variable means for adjusting the inductance, the variable means is provided. Therefore, if the inductance of the duct portion is changed as necessary, preferable acoustic control can be performed.

[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 circuit diagram of the conventional earphone shown in FIG.

4A is a central cross-sectional view of an earphone according to an 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 an 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) 18 Duct Section 19 Outer Cylinder 20 Housing 22 Cylindrical Section 26 Through Hole 27 Braking Plate

Claims (1)

[Claims] 1. An acoustic transducer and a housing to which the acoustic transducer is attached, the housing having a duct portion for radiating a sound emitted from a rear surface of the acoustic transducer to the outside. Headphones characterized in that a variable means for adjusting the inductance is provided in the section.