JPS646636Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a headphone with improved frequency characteristics in the bass range, and is particularly suitable for application to a small-diameter inner-ear type headphone.

Background technology and its problems The low frequency reproduction limit of conventional open-air headphones is mainly due to the vibration system compliance C _nd
(reciprocal of stiffness S) and equivalent mass of the vibration system M _d
As shown in Figure 1, the response in the low frequency range below ₀ was reduced. This ₀ is approximately given by ₀ 1/2π√ _{d nd} (c/s), and to lower ₀ , the compliance of the vibration system C _nd
(cm/dyne) or the equivalent mass M _d (gr) needs to be increased. However, compliance
There is a limit to how high C _nd can be made, and increasing the equivalent mass M _d of the vibration system will lead to a decrease in sensitivity and deterioration of acoustic characteristics in the high frequency range.
There is a limit to how heavy M _d can be made.

Moreover, as is well known, this low frequency resonance frequency _{is 0.}
Since headphones tend to be louder with smaller diameters, earphones with smaller diameters have the disadvantage of making it difficult to hear reproduced sounds in the bass range.

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 that sandwich the magnet 1 from both sides, and the earphone is inserted into a magnetic gap 4. A driver unit 7 as an acoustic transducer is constructed by incorporating a diaphragm 6 coupled to a voice coil 5 into the front surface, and the outer peripheral portion of the driver unit 7 is attached to a housing 8. The through hole 9 in the center of the driver unit 7 is filled with a sound absorbing material 10, the damping layer 12 is provided on the back side of the through hole 11, and the housing 8 is provided with several through holes 13 to provide frequency characteristics. is controlled.

Therefore, if the above configuration is expressed as an acoustic equivalent circuit,
It will look like Figure 3. Here, M _d , C _nd and R _d
are the equivalent mass, compliance, and acoustic resistance of the vibration system, respectively, V _s is the signal source, R _a is the acoustic resistance due to the sound absorbing material 10 and damping layer 12, and R _b and C _b constitute a parallel circuit. are the acoustic resistance due to the through hole 13 of the housing 8 and the compliance due to the rear space (ie, back cavity) of the housing, respectively.

In addition, in this Figure 3, the symbol G is enclosed.
M _cup , C _cup and R _cup are the equivalent mass, compliance and acoustic resistance formed by the ear canal when the earphone is inserted into the ear canal, respectively.

However, due to the through hole 13 in the housing 8, the acoustic resistance
Since R _b is negligibly small compared to R _a , and C _d is also almost negligible, these R _b
The effects of C and C _b are small, and the acoustic equivalent circuit in FIG. 3 is approximately a series resonant circuit of M _d , C _nd , R _d and R _a . Therefore, as mentioned above, the bass resonance frequency _{is 0.}
is given by ₀ 1/2π√ _{d nd} and does not become low. Also, as shown in Figure 1, when R _a is small, a peak appears in the characteristic near ₀ , and only the sounds around that area are emphasized and resonate. It becomes a sound. On the other hand, when R _a is large, the characteristics begin to deteriorate from frequencies higher than ₀ , and bass reproduction becomes insufficient.

Purpose of the invention The present invention was devised in view of the above-mentioned circumstances, and its purpose is to improve the rear side of the acoustic transducer without making any particular changes to the structure of the conventionally used driver unit (i.e., acoustic transducer). The object of the present invention is to improve the response in the low frequency range by changing the acoustic equivalent circuit. In other words, the object is to provide a headphone that can obtain a low frequency response comparable to that of a large diameter headphone with a small diameter.

Summary of the invention In order to achieve the above object, the present invention consists of an acoustic transducer and a casing to which the acoustic transducer is installed, and is capable of emitting sound emitted from the rear surface of the acoustic transducer to the outside. In order to add an inductance component to the acoustic equivalent circuit, a duct portion whose length is selected to be larger than the inner diameter is provided in the housing.

By configuring as described above, the bass resonance frequency ₀ of the entire acoustic equivalent circuit is lowered, so the response in the bass range is improved. Unlike this, it is possible to obtain playback sound with a rich bass range.

Embodiment Hereinafter, an embodiment in which the present invention is applied to an inner-ear headphone (ie, an earphone) will be described based on the drawings.

As shown in FIGS. 4A and 4B, the earphone of the present invention uses the same acoustic transducer (i.e. driver unit) 7 as shown in FIG. are given the same reference numerals and their explanations will be omitted. In this embodiment, the through hole 11 on the back side of the driver 7 and the central through hole 9 are provided with a damping material (i.e., sound absorbing material) such as cloth with a resistance component of almost zero, such as natron mesh, or urethane. Good too.

The casing 20 is formed into a conical shape constricted at the rear except for the portion related to the lead wire 21, and an upper duct 22 and a lower duct 23 facing upward and downward, respectively, are formed at the rear end. It is formed. The upper duct 22 has an opening 24, and the lower duct 23 has a flexible joint 2.
5 is fitted into the housing 20, and a lead wire 21 is introduced into the housing 20 via this joint 25. In addition,
The lengths of these ducts 22, 23 are each selected to be sufficiently larger than their inner diameters (ie, the diameter of opening 24).

A plurality of through holes 26 are formed on the side surface of the casing 20, and a brake plate 27 made of urethane or the like is provided on the inside surface of these through holes 26. The driver unit 7 is located at the front of the housing 20.
A variety of gently curved disk-shaped protection plates are installed to cover the front surface of the That is, these protection plates consist of, in order from the inside, the protection plate 28, which is made of punched metal with a mesh having a relatively large hole diameter and mechanically protects the driver unit 7 from external pressure, etc., and the base fabric on the outside of the protection plate 28. It is composed of a dust-proof protection plate 29 and an ear hole protection plate 30 made of punched metal with a mesh having a small hole diameter.

FIG. 5 shows the acoustic equivalent circuit of the earphone according to the present invention constructed as described above. Here, M _d , C _nd and R _d respectively relate to the vibration system of the driver unit 7, as in the case of FIG. 3 above. Also, R _a is the through hole 11 of the driver 7.
And due to the acoustic resistance due to the central through hole 9, approximately R _a ≒
It is 0. Further, C _b is the compliance due to the back cavity due to the conical shape of the housing 20, R _b is the acoustic resistance due to the brake plate 27, and L _d
and R' _d are the inductance (equivalent mass) and acoustic resistance due to the ducts 22 and 23, and R' _d is very small. Therefore, in the case of the earphone according to the present invention, the equivalent mass L _d of the ducts 22 and 23 is added to the equivalent mass M _d of the vibration system. Therefore, the braking on the back side of the earphone is a parallel resonant circuit of L _d , C _{b ,} and R _b , which is applied to the series resonant circuit of M _d , C _nd , and R _d .

As mentioned above, the bass resonance frequency of the entire acoustic equivalent circuit of this earphone is determined by the inductance (equivalent mass) L _d from the bass resonance frequency ₀ of the driver unit 7 itself, as shown in Fig. 6. is also lowered to a low ′ ₀ , so the range,
In particular, it can widen the bass range. Further, as shown in FIG. 6, when the resistance R _b connected in parallel with L _d is reduced, '_0' increases, while when R _b is increased, the midrange falls. Therefore, by appropriately selecting R _b with respect to L _d , it is possible to widen the range and flatten the range from bass to treble, enhance the treble range while widening the range, or obtain desired frequency characteristics. You can try to get it.

Regarding high frequencies, increasing _Rb increases the level of high frequencies necessary for headphone reproduction in terms of hearing.

Note that, for example, acoustic control can also be performed by making the length l 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 using the same driver unit as this, the duct 22 shown in Figs. 4A and 4B has a diameter of 3 mm x 20 mm. This figure shows a comparison with the sound pressure-frequency characteristic B of the earphone according to the present invention, which is provided with a duct. As is clear from this figure, ₀ is decreasing from 220Hz to 150Hz. It can also be seen that the level of high frequencies around 4KHz, which is necessary for headphone playback, increases. The unit in both FIGS. 2 and 4 has a diameter of φ16.

The second embodiment shown in FIG. 8 is a second embodiment in which the shape of the duct 31 is inverted U-shaped and the opening 32 is directed downward in consideration of dust prevention, and the length of the duct 31 is made longer as desired. It shows
In other respects, this embodiment is exactly the same as that described in the first embodiment. Even if the shape of the duct 31 is made into an inverted U-shape, it is clear that this duct 31 exhibits the function and effect as the inductance (equivalent mass) L _d , so overall, this second embodiment The earphone in Embodiment 1 can also exhibit the same effects as the earphone in the first embodiment.

Effects of the invention As explained above, the headphone of the invention has the following effects:
It consists of an acoustic transducer and a casing to which the acoustic transducer is attached, and is larger than the inner diameter in order to be able to emit the sound emitted from the rear surface of the acoustic transducer to the outside and to add an inductance component to the acoustic equivalent circuit. A duct portion having a selected length is provided in the above-mentioned housing.

Therefore, since the inductance due to the duct section is added to the acoustic equivalent circuit of the acoustic transducer,
The bass resonance frequency of the entire acoustic equivalent circuit of the headphone according to the present invention is lowered by the inductance to a value lower than the bass resonance frequency of the acoustic transducer itself. Therefore, according to the present invention, the response in the bass range is improved, and therefore, even if the headphone uses the same size acoustic transducer, it can reproduce sound with a rich bass range, unlike conventional headphones. can be obtained. And speaking of the bass range, even with a small diameter, you can get the response of a large diameter, which is extremely advantageous.

[Brief explanation of drawings]

Figure 1 is a sound pressure characteristic diagram of conventional headphones;
Figures 4 and 3 show a central longitudinal sectional view of a conventional headphone and its acoustic equivalent circuit diagram, and Figures 4 to 6 show an embodiment of the earphone according to the present invention.
The figure is a central vertical sectional view, Figure 4B is an external perspective view, and Figure 5
The figure is an acoustic equivalent circuit diagram, Figure 6 is a bass characteristic diagram, and Figure 7 is a diagram of bass characteristics.
The figure is a comparison diagram of the sound pressure-frequency characteristics of the conventional type and the one according to the present invention, and FIG. 8 is an external perspective view showing a second embodiment according to the present invention. In addition, in the symbols used in the drawings, 1...Magnet, 2...Yoke, 3...Plate, 4...Magnetic gap, 5...Voice coil, 6...Diaphragm, 7...Driver unit (acoustic transducer) ),
20... Housing, 22, 23, 31... Duct, 2
6... through hole, 27... brake plate.

Claims (1)

[Scope of utility model registration request] Consisting of an acoustic transducer and a housing to which this acoustic transducer is attached, the housing is larger than the inner diameter in order to be able to emit the sound emitted from the rear surface of the acoustic transducer to the outside and to add an inductance component to the acoustic equivalent circuit. A headphone characterized in that a duct portion having a selected length is provided in the casing.