JP5849296B1 - Sealed earphone with communication part - Google Patents

Abstract

When using an earphone, the external noise is reduced to make it easier to hear the sound from the earphone, and the sound characteristics that are uncomfortable to other people are reduced while achieving a balanced frequency characteristic over a wide band. To do. An ear tip is attached to the sound conduit or a sound conduit adapted to the shape of the ear hole is used to increase the sealing degree, and the internal space and the external space of the housing for housing the electroacoustic transducer are in acoustic communication. The inner space of the housing is divided into three parts, a front space, an inner space, and a back space, by the electroacoustic transducer and the intermediate housing, between the front space and the inner space, and between the inner space and the back space. Are communicated with each other by a communication portion forming a relatively small tubular space. [Selection] Figure 2

Description

The present invention relates to a sealed earphone that is used by inserting a sound emitting portion into an ear canal entrance. In particular, the present invention relates to a sealed earphone characterized by high sound insulation performance.

Sealed earphones have a sound generating part whose back is sealed, and the ear pad that is the part that is inserted into the ear canal is formed of elastic soft plastic or rubber, etc. As an earplug structure. Since the sealed earphone can be attached by inserting the ear pad into the ear canal, it can be reliably attached to the entrance of the outer ear to be sound-insulated. In addition, since the ear pad can be easily elastically deformed according to the shape of the ear canal by a material having flexibility, a good wearing feeling can be obtained.

In addition, recently, it is called custom IEM (IN EAR MONITOR) and an ear shape (impression) is collected, and the external shape of the sound conduit is created based on the shape of the user's ear hole. Earphones with a good degree and wearing feeling can also be obtained.

Sealed earphones that are inserted into the ear canal entrance have good sealing performance and high sound insulation performance, making it difficult to hear external noise, providing high sound pressure sensitivity and allowing you to hear faint sounds even in noisy locations. It is. Moreover, since it can be used by inserting it into the ear canal entrance, there is an advantage that it is easy to reduce the size and weight.

When a general inner-ear type earphone is hermetically sealed so as not to leak sound, the equivalent circuit is as shown in FIG. 5 (a), and the frequency characteristic is as shown by a one-dot chain line in the graph of FIG. It is flat and the treble range decreases sharply, resulting in only low and medium sounds without treble. Therefore, in order to solve this problem, the technique disclosed in Patent Document 1 uses a ring-shaped slit formed between a bypass ring equipped with an electroacoustic transducer and a unit case (of an electroacoustic transducer) for acoustics. A passage is created and the front and back surfaces of the diaphragm are acoustically coupled. (Patent Document 1)

An equivalent circuit of the inner-ear type earphone thus configured is as shown in FIG. FIG. 5B shows diaphragm equivalent mass m1 / diaphragm equivalent stiffness S1 / diaphragm equivalent acoustic resistance r1 and voice coil driving force V, outer ear hole equivalent stiffness Sc depending on the volume of the ear hole, and backspace equivalent stiffness on the back of the earphone. It shows that the series resonance circuit composed of S0 is bypassed by an acoustic path composed of the first communication path equivalent mass mp and the first communication path equivalent acoustic resistance rp.

The frequency characteristic in this case is as shown by a broken line in FIG. Although it becomes relatively flat as a whole and the treble part has sufficiently high characteristics, the problem remains that the attenuation of the bass part of 200 Hz or less is large.

There is a proposal of a sealed earphone that solves this problem. For example, in order to prevent the occurrence of sound como in the sound emitting space, the rear surface that communicates with the sound emitting space in the housing that is sealed when the headphone is attached to the ear hole by a slit provided on the outer peripheral edge of the driver unit There was something that communicated with external space through space. (Patent Document 2)

As a result, it is said that the occurrence of sound comorbidity is prevented, and not only the improvement in the low frequency range but also the improvement of the frequency characteristics in the entire region including the high frequency range is achieved. However, there is an opening that communicates with the external space, so it can not be said that the sound insulation performance is high. There was a problem of hearing sound and causing trouble.

Japanese Patent Publication No. 1-101895 Patent Publication 2005-191663

In a sealed inner-ear type earphone, there is a problem of providing a frequency characteristic that balances low, medium and high sounds, and at the same time minimizing sound leakage.

The present invention has been made in view of the above problems,
In using ear pads inserted into the ear canal entrance,
The interior of the housing that houses the electroacoustic transducer is separated into three independent spaces, a front space, an inner space, and a backspace, by the wall of the electroacoustic transducer and the intermediate housing.
The sealed earphone is characterized in that the front space and the inner space communicate with each other only by the first and the inner space and the back space by the second relatively small tubular space.

In the sealed earphone of the present invention, an equivalent circuit is as shown in FIG. That is, there is a tubular space that communicates the front space and the inner space in parallel with the electroacoustic transducer. In other words, this is a bypass circuit composed of a first communication path equivalent acoustic resistance rp and a first communication path equivalent mass mp in parallel with the equivalent circuit of the electroacoustic transducer. There is a tubular space that connects the inner space and the back space. This is a series impedance composed of the second communication path equivalent acoustic resistance r2 and the second communication path equivalent mass m2 in series with the equivalent circuit of the electroacoustic transducer.

The frequency characteristics of the sealed earphone can be adjusted by appropriately changing these circuit elements. Since the number of circuit elements is increased, the frequency characteristics can be easily adjusted.

Also, a bypass circuit in parallel with the stiffness of the external space indicates leakage from the gap between the bushing and the wire. Since the acoustic resistance rl of the passage forming the bypass circuit is large, actual sound leakage is small.

Since it is connected from the inner space to the back space having a larger volume, the characteristics of the bass range are mainly improved.

The ear pad contacts the inner surface of the inner ear without any gap, and the sound emitted from the tip of the ear pad does not go out to the outside space. Also, since the housing that houses the electroacoustic transducer has no opening to the external space, basically no sound goes out to the external space. As a result, a sealed earphone with less sound leakage can be realized.

Outline drawing of sealed earphone Side cross-sectional view of sealed earphone Rear view of sealed earphone Side cross-sectional view for explaining the method of mounting the communication portion and the acoustic resistance material Acoustic equivalent circuit of sealed earphone Sound leakage characteristics Sound pressure-frequency characteristics of sealed earphones

Examples of the sealed earphone according to the present invention will be described below.

FIG. 1 is an outline sketch of a sealed earphone 1 according to the present invention. FIG. 2 is a side sectional view of the sealed earphone 1 at the center position in the depth direction when viewed from the side. The main part of the sealed earphone 1 includes an electroacoustic transducer 11, a front housing 13, an intermediate housing 17, a rear housing 14, and an ear pad 15, and three of them are closely fitted. (The front housing 13, the intermediate housing 17, and the rear housing 14 are collectively referred to as a housing.) FIG. 3 is a cross-sectional view perpendicular to the paper plane indicated by AA ′ in FIG. 2 with the intermediate housing 17 and the rear housing 14 removed. It is the rear view which looked at the left direction of the figure from the position.

An electroacoustic transducer 11 is housed inside the front housing 13. As can be seen in FIG. 3, the electroacoustic transducer 11 is fitted into the partition wall 134 formed inside the front housing 13 without a gap. Therefore, the front housing 13 and the intermediate housing 17 are in acoustic communication only by the tubular space of the communication portion described later, and there is no other acoustic passage. A sound guide tube 131 is formed in front of the front housing 13 (left direction in the figure), and an ear pad 15 made of a flexible and stretchable material is fitted into the distal end portion thereof. As shown in FIG. 2, the rear part (right side in the figure) of the front housing 13 and the front part of the intermediate housing 17 and the rear part of the intermediate housing 17 are fitted, and the inner and outer surfaces of the three housings are smoothly connected. The connecting part is sealed.

The ear pad 15 has a circular cross section when viewed from the front direction (left side in the figure), and can be used by any user. However, it may be a custom IEM that takes the shape of a specific user's individual ear hole and has a sound conduit inserted into the ear hole with an external shape corresponding thereto. The sealed earphone 1 is used by inserting the ear pad 15 into the outer ear hole. At this time, the periphery of the ear pad 15 is in close contact with the skin of the outer ear hole without any gap, and the space on the front surface of the electroacoustic transducer 11 and the outer ear hole are The interior space together forms an outer ear canal space. At this time, the sound generated through the sound guide tube 131 from the front surface (left side in the drawing) of the electroacoustic transducer 11 of the sealed earphone 1 does not leak into the external space.

A spiral tube 130 is accommodated at a position between the sound guide tube 131 and the electroacoustic transducer 11 in the front housing 13. The spiral tube 132, which is another invention of the inventor, divides the sound wave path into two, and the difference between the lengths of the two paths is determined by the wavelength of the frequency that generates the closed spatial resonance of the ear canal. It is a member for equalizing half the length. It is not directly related to the present invention.

As shown in FIGS. 2 and 3, there is a communication portion 12 between a part of the partition wall 134 and the bulged portion of the upper portion of the front housing 13. A space Ra is defined. There is a hole 121 near the center of the communication portion 12. That is, the hole 121 is a tubular space that communicates the front space F and the inner space Ra.

The hole 121 is filled with an acoustic resistance material 124 as shown in FIG. The material of the acoustic resistance material is foamed plastic, nonwoven fabric or the like. In some cases, the hole 121 is not filled with the acoustic resistance material 124.

FIG. 4 is a cross-sectional view illustrating a method of mounting the communication portion and the acoustic resistance material. FIG. 4A shows a method in which a hole 121 is formed in the communication portion 12 and an acoustic resistance material 124 is filled in the hole 121 as shown in FIG. There is an advantage that the resistance value can be adjusted by the length dimension of the acoustic resistance material 124 and the pressure at the time of filling. FIG. 4B shows a method of attaching the acoustic resistance material 124 so as to cover the opening portion of the hole 121 of the communication portion 12. FIG. 4C shows a method in which a thin pipe 122 is embedded in the communication portion 12 and the acoustic resistance material 124 is filled inside the pipe 122. There is an advantage that the equivalent mass can be adjusted by selecting the length of the pipe 122. FIG. 4D shows a method in which a thin pipe 122 is embedded in the communication portion 12 and an acoustic resistance material 124 is attached so as to cover the end of the pipe 122. FIG. 4 (e) shows a case in which the hole 121 is opened in the communication portion 12, and the acoustic resistance material is not filled or attached. Among these, an appropriate method can be used.

The intermediate housing 17 forms a partition wall 171 having a lid shape that covers the entire back surface of the electroacoustic transducer 11. A fine hole 172 is opened at one place of the partition wall 171 of the intermediate housing 17. The fine hole 172 is a tubular space that communicates the inner space Ra and the back space Rb. An acoustic resistance material 173 is attached to the opening on the right side of the fine hole 172. There may be a case where the acoustic resistance material is not pasted or filled in the fine holes 172. In addition to the fine holes 172, there is a passage for passing a wire for sending an electric signal to the electroacoustic transducer 11, and the wire and the passage are sealed with an appropriate adhesive or filler.

The rear housing 14 has a lid shape that covers the entire back surface of the intermediate housing 17, and forms a back space Rb between the rear housing 14 and the intermediate housing 17. The back space Rb accommodates a knot for retaining a wire (not shown) for sending an electric signal to the electroacoustic transducer 11.

A bushing 16 is fitted below the rear end portion of the rear housing 14. The bushing 16 is formed with a wire passage 161 for passing a wire for sending an electric signal to the electroacoustic transducer 11. In FIG. 2, the illustration of the wire is omitted. There is a slight gap between the wire passage 161 and the wire due to a difference in dimensions due to normal molding and assembly.

Part of the frame material of the electroacoustic transducer 11 forms a duct 112. One of the ducts 112 (the left side in the figure) is a bottom, and other than the hole 113 described below is closed. A thin hole 113 is formed in a part of the bottom, and penetrates to the space on the back side of the vibration plate 111.

In addition, a hole 114, a hole 115, a hole 116, and a hole 117 are formed in the center of each of the frame material, yoke, magnet, and pole piece of the electroacoustic transducer 11, respectively. The positions of the respective holes are overlapped and penetrate to the space at the center of the back side of the vibration plate 111.

In the sealed earphone 1 having such a structure, a sound wave generated on the front side (right side in the drawing) of the vibration plate 111 of the electroacoustic transducer 11 passes through two paths formed by the spiral tube 132 and passes through the acoustic path 133. Via to reach the ear canal. At this time, the front space F on the front side of the vibration plate 111 and the inner space Ra on the back side are acoustically connected by the hole 123. Further, the inner space Ra and the back space Rb are acoustically connected by the fine holes 172. In the back space Rb, there is no positive opening that allows the sound wave to go out to the outside space, except for the gap between the bushing 16 and the wire (not shown).

FIG. 6 shows the result of evaluating the sound leakage characteristics of the sealed earphone 1 described above. This is measured by inserting the ear pad 15 into a dummy outer ear hole, placing the microphone in a position opposite to the sound generation direction of the sealed earphone 1 (the side having the ear pad), and operating the sealed earphone 1.

A graph shown by a broken line in FIG. 6 is a case where the micro hole 172 of the intermediate housing 17 is closed, and a graph shown by a solid line is a case where the micro hole 172 of the intermediate housing 17 is opened. The broken line graph shows that the sound leakage is extremely small because the rear portion of the electroacoustic transducer 11 is covered by the partition wall 171 and the rear housing 14 of the intermediate housing 17. In the solid line graph, the sound comes out from the inner space Ra to the back space Rb, and further leaks out from the gap of the bushing 16 to the external space. The sound is almost inaudible.

An acoustic equivalent circuit of the sealed earphone of the present invention is shown in FIG. Here, the electroacoustic transducer equivalent circuit 20 includes a diaphragm equivalent stiffness S1, a diaphragm equivalent acoustic resistance r1, a diaphragm equivalent mass m1, and a voice coil driving force V connected in series. The outer ear equivalent stiffness Sc forming the equivalent circuit 30 and the inner space equivalent stiffness S2 forming the equivalent circuit 40 of the inner space Ra are represented by a closed circuit connected in series. A first communication path equivalent circuit 60 comprising a first communication path equivalent acoustic resistance rp and a first communication path equivalent mass mp is connected in parallel to the electroacoustic transducer equivalent circuit 20 to form a bypass circuit. .

Further, a second communication path equivalent circuit 70 composed of the second communication path equivalent acoustic resistance r2 and the first communication path equivalent mass m2 connects the equivalent circuit 40 in the inner space and the equivalent circuit 50 in the back space. . Here, the backspace equivalent circuit 50 includes a backspace equivalent stiffness S0. Further, in parallel with the equivalent circuit 50 of the back space, there is a leakage passage equivalent circuit 80 including a leakage passage equivalent acoustic resistance rl and a leakage passage equivalent mass ml, and the leakage passage connecting the back space Rb and the external space. Represents.

In this equivalent circuit, the outer ear hole space composed of the outer ear hole and the front space F on the front surface side of the vibration plate 111 of the electroacoustic transducer 11 and the inner space Ra on the rear surface include the first communication path equivalent mass mp and the first space. Are further bypassed by the communication portion represented by the communication path equivalent acoustic resistance rp, and further represented by the second communication path equivalent mass m2 and the second communication path equivalent acoustic resistance r2 via the inner space Ra. The communication portion connecting the inner space Ra and the back space Rb reaches the back space Rb, and further, the sound passes through the leak passage equivalent mass ml indicating the gap between the bushing 16 and the wire and the leak passage equivalent acoustic resistance rl, and the sound is transmitted to the external space. Indicates that it is leaking.

Since the inner diameter and length of the hole 121 of the communication part 12 and the acoustic resistance material 124 can be designed freely, the first communication path equivalent mass mp and the first communication path equivalent acoustic resistance rp are adjusted to desired values. Is easy. Similarly, it is easy to adjust the second communication path equivalent mass m2 and the second communication path equivalent acoustic resistance r2 to the desired values for the fine holes 172 of the intermediate housing 17 as well. The frequency characteristics of the sealed earphone 1 can be adjusted by adjusting these values.

FIG. 7 shows the measured frequency characteristics of the sealed earphone. The solid line graph shows the result of measurement of the sealed earphone 1 of the present invention, and the broken line shows the result of measurement with the fine hole 172 of the intermediate housing 17 closed for comparison.
In the broken line graph, the attenuation is 1 kHz or less, particularly 500 Hz or less, and the bass is weak. On the other hand, in the solid line graph, 500 Hz or less is relatively high, realizing a sound with a low frequency, and realizing a characteristic in which the entire frequency range is balanced.

DESCRIPTION OF SYMBOLS 1 Sealed earphone 11 Electroacoustic transducer 111 Vibration plate 112 Duct 113 Hole 114 Hole 115 Hole 116 Hole 117 Hole 12 Communication part 121 Hole 122 Pipe 124 Acoustic resistance material 13 Front housing 131 Sound guide pipe 132 Spiral pipe 133 Acoustic path 134 Partition Wall 14 Rear housing 15 Ear pad 16 Bushing 161 Wire passage 17 Intermediate housing 171 Bulkhead 172 Micro hole 173 Acoustic resistance material 20 Electroacoustic transducer equivalent circuit 30 Equivalent circuit of outer ear space 40 Equivalent circuit of inner space 50 Back space equivalent circuit 60 1 communication path equivalent circuit 70 2nd communication path equivalent circuit 80 Leakage path equivalent circuit F Front space Ra Inner space Rb Back space S1 Diaphragm equivalent stiffness r1 Diaphragm equivalent acoustic resistance m1 Equivalent mass of diaphragm V Boy Scoil driving force Sc Outer ear equivalent stiffness S2 Inner space equivalent stiffness S0 Backspace equivalent stiffness rp First communication path equivalent acoustic resistance mp First communication path equivalent mass r2 Second communication path equivalent acoustic resistance m2 Second communication path Equivalent mass rl Leakage passage equivalent acoustic resistance ml Leakage passage equivalent mass

Claims (2)

In a sealed earphone used by inserting an earpad into the ear canal entrance,
The interior of the housing that houses the electroacoustic transducer is separated into three independent spaces, a front space, an inner space, and a backspace, by the wall of the electroacoustic transducer and the intermediate housing.
The front space and the inner space communicate with each other only by the first and the inner space and the back space by the second tubular space , respectively .
Sealed earphones, wherein Rukoto first and to adjust the inner diameter and length of the tubular space of the second to have a desired frequency characteristic. The sealed earphone according to claim 1,
First tubular space, at least one of the tubular space of the second, Ri inside or over the inlet are filled with acoustic resistance member attached to acoustic resistance member tare,
Sealed earphones, wherein Rukoto to have a desired frequency characteristic by adjusting the equivalent mass and equivalent acoustic resistance of the acoustic resistance member.

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