Headphone

This is a continuation of application Ser. No. 08/122,309 filed Sep. <b>17, 1993, abandoned.</b>

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a headphone and more particularly to a headphone provided with a housing containing a drive unit and adapted to reproduce sound by means of the drive unit.

2. Description of the Related Art

The headphone is used for personally enjoying reproduced sound of music and the like. Such headphones are generally divided into two types: open-air type and closed type.

The headphone of the open-air type has a permeable ear pad and has the housing containing the drive unit and provided with a through hole formed therein. Therefore, when a listener wears the headphone to listen to a reproduced sound, the sound produced within the housing easily leaks out and also sound from the outside can be heard by the listener. While the headphone of the open-air type has acoustic transmissibility between inside and outside the housing and, hence, it allows the sound to be heard as a natural sound, the sound is greatly attenuated in the low-pitched sound range below f0 (the lowest resonance frequency) and tends to lack the low-pitched sound component.

On the other hand, the closed type headphone has the housing containing the drive unit closed and has the ear pad keeping sound from leaking out. Although a rich sound characteristic in the low-pitched sound range can be obtained from the closed type, it is difficult to obtain a natural sound from this type.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a headphone capable of obtaining both the merit of the open-air type headphone introducing the external sound therein thereby providing a refreshing sound and the merit of the closed type headphone having a rich sound characteristic extended over the low-pitched sound range.

A headphone according to the present invention is structured such that a window hole is formed in the housing containing a drive unit and the window hole is covered with a diaphragm, so that the external sound is transmissible through the window hole, and hence a listener putting on this headphone can hear the external sound while the reproduced sound in the low-pitched sound range below f0 is not attenuated. Thus, the listener can perceive a refreshing and natural sound.

Further, since the window hole is adapted to be shut when necessary, the headphone can be used also as that of closed type by shutting the window hole.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an overall structure of an embodiment of the invention;

FIG. 2 is a side view of an overall structure of the embodiment of the invention;

FIG. 3 is a side view, with the principal portion enlarged, of the embodiment of the invention;

FIG. 4 is a sectional view taken along section line IV—IV of FIG. 3;

FIG. 5 is a sectional view of the embodiment of the invention when it is put on the head;

FIG. 6 shows characteristic curves of external sound to the embodiment of the invention;

FIG. 7 shows characteristic curves of reproduced sound in the embodiment of the invention; and

FIG. 8 is a sectional view, corresponding to FIG. 4, with the principal portion of another embodiment of the invention enlarged.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 to FIG. 5 show a stereo headphone according to an embodiment of the invention. The headphone has a pair of housings <b>10</b> for the left and right ears as shown in FIG. <b>1</b>. As shown in FIG. <b>1</b> and FIG. 2, each housing <b>10</b> has a form as obtained by longitudinally dividing an egg in two. The housing <b>10</b> is supported by a hanger <b>11</b> for rotation about its support shaft. The hanger <b>11</b> is provided with a slide arm <b>12</b> in the shape of the inverted letter U.

The slide arm <b>12</b> is slidably coupled to a supporting member <b>13</b>. The supporting members <b>13</b> on both left and right sides are coupled by a head band <b>14</b>. The head band <b>14</b> is provided with a resilient force biasing the same inwardly as indicated by arrows Y and Y′ and, hence, when the headphone is put on the head, each of the housings <b>10</b> is resiliently pushed against each ear. From the housings <b>10</b>, cords <b>15</b> are led out and the other ends of the cords <b>15</b> are adapted to be connected to an apparatus such as a radio receiver or a tape recorder. Through the cords <b>15</b>, a sound signal from the radio receiver or tape recorder is supplied to a coil for the drive unit within the housing <b>10</b>.

An example of structure of a housing <b>10</b> for the right ear will be described below with reference to FIG. 3, FIG. 4, and FIG. <b>5</b>.

While the housing <b>10</b> for the right ear is shown in FIG. 3, FIG. 4, and FIG. 5, that for the left ear, not shown, is provided symmetrical to that for the right ear.

FIG. 4 shows a state of a headphone with its window hole <b>28</b> shut by a lid member <b>32</b>, while FIG. 5 shows the same put on the head <b>60</b> of a listener, with the lid member <b>32</b> removed from the window hole <b>28</b>.

The housing <b>10</b> is formed of a cover <b>29</b>, made of a synthetic resin in the shape of a dome, and a baffle plate <b>19</b> fixed on the inside of the cover <b>29</b>, and a drive unit <b>20</b> is adapted to be supported on the baffle plate <b>19</b>.

Inner space of the housing <b>10</b> is divided by the baffle plate <b>19</b> and the drive unit <b>20</b> in two chambers, a front chamber <b>10</b>a and a rear chamber <b>10</b>b.

The drive unit <b>20</b> is formed of a magnetic circuit <b>20</b>a connected with the end of the cord <b>15</b> to be supplied with the audio signal therethrough and a diaphragm <b>20</b>b in the shape of a dome to be driven by the signal passed through the magnetic circuit <b>20</b>a.

In the side wall portion of the baffle plate <b>19</b>, there is formed a through hole <b>21</b> and an acoustic resistance material <b>22</b> such as felt is attached to the through whole <b>21</b> so as to cover it.

An ear pad <b>23</b> in the shape of an oval ring is attached to the circumference of a sound emitting opening <b>25</b> of the front chamber <b>10</b>a of the housing <b>10</b> as shown in FIG. <b>3</b>. More specifically, the ear pad <b>23</b> formed of a cushion material <b>23</b>a such as urethane and a protecting cover <b>23</b>b of synthetic leather with no permeability enclosing the cushion material <b>23</b>a is attached to a flange portion provided on the circumference of the sound emitting opening <b>25</b> integrally formed with the baffle plate <b>19</b>.

When the headphone is put on the head <b>60</b> of a listener as shown in FIG. 5, the ear pad <b>23</b> is tightly pressed on the head <b>60</b> by the resilience of the head band <b>14</b> and the flexibility of the ear pad <b>23</b> ensures that no sound leaks out therethrough.

There is formed the window hole <b>28</b> of a circular form in the housing cover <b>29</b> in a position virtually confronted with the rear side of the drive unit <b>20</b>. At the peripheral portion of the window hole <b>28</b>, there is formed a screwed groove portion <b>29</b>a, and at its bottom end, there are formed, integrally with the housing cover <b>29</b>, a flange portion <b>29</b>b and a cylindrical portion <b>29</b>c projecting inward and perpendicularly to the flange portion <b>29</b>b. At the cylindrical portion <b>29</b>c, there is provided a second diaphragm <b>30</b> fixed by a fixing ring <b>31</b> to cover the window hole <b>28</b>.

The second diaphragm <b>30</b> is smaller in diameter than the diaphragm <b>20</b>b and is not provided with a drive unit.

Reference numeral <b>27</b> denotes a net attached to the baffle plate <b>19</b> in confronting relationship with the diaphragm <b>20</b>b for mechanically protecting the diaphragm <b>20</b>b. Reference numeral <b>34</b> denotes a net attached to the flange portion <b>29</b>b for protecting the diaphragm <b>30</b>.

The window hole <b>28</b> is adapted to be opened and shut by a lid member <b>32</b>. More specifically, the lid member <b>32</b> is integrally provided with a cylindrical lip <b>33</b> on its periphery and the cylindrical lip <b>33</b> is provided with a screwed portion <b>33</b>a on its outer wall, and the screwed portion <b>33</b>a is adapted to be threaded with the screw grooves <b>29</b>a. Accordingly, it is possible both to shut the window hole <b>28</b> with the lid member <b>32</b> as shown in FIG. <b>4</b> and to remove the lid member <b>32</b> from the window hole <b>28</b> as shown in FIG. <b>5</b>.

The transmission characteristics (frequency-sound pressure characteristics) of medium- and high-pitched external sound when the lid member <b>32</b> is removed from the window hole <b>28</b>, and when the window hole <b>28</b> is shut by the lid member <b>32</b>, of the headphone of the present embodiment are obtained as shown in FIG. <b>6</b>. More specifically, the characteristic of the sound transmitted to the ear from outside the housing <b>10</b> when the lid member <b>32</b> was removed from the window hole <b>28</b> (in the state shown in FIG. 5) was obtained as shown by the curve A, and the characteristic when the window hole <b>28</b> was shut by the lid member <b>32</b> (in the state shown in FIG. 4) was obtained as shown by the curve B. Namely, it is known that, when the lid member <b>32</b> is removed from the window hole <b>28</b>, the external sound in the range higher than 800 Hz is heard better than when the window hole <b>28</b> is shut with the lid member <b>32</b>. In this case, the resonance frequency of the diaphragm was around 1300 Hz. Further, the frequency characteristics (frequency-sound pressure characteristics) of the reproduced sound by the headphone were obtained as shown in FIG. 7, i.e., the frequency characteristic when the lid member <b>32</b> was removed from the window hole <b>28</b> was obtained as indicated by the characteristic curve C and that when the window hole <b>28</b> was shut by the lid member <b>32</b> was obtained as indicated by the characteristic curve D. In this case, the characteristics are virtually the same though there is some difference between them in the range from 300 Hz to 1.8 KHz. For reference, a reproducing characteristic by the headphone was measured in the state of the headphone having the lid member <b>32</b> removed from the window hole <b>28</b> and, further, having the diaphragm <b>30</b> removed from the cylindrical portion <b>29</b>c, and a characteristic as indicated by the curve E was obtained. According to this curve, while the sound pressure was lowered in the range lower than 60 Hz, damping around f0, the lowest resonance frequency (about 180 Hz), was not sufficient and the sound was greatly increased around there, and thus, the balance in the entire range was bad.

The characteristic curves in FIG. <b>6</b> and FIG. 7 were obtained by performing measurement with an artificial human head used and a sound concentrating microphone disposed in the position corresponding to the tympanic membrane of the ear.

From the above, it is known that, by using the headphone of the present embodiment and listening to the reproduced sound by this headphone with its lid member <b>32</b> removed from the window hole <b>28</b>, a totally well-balanced sound, not attenuated in the low-pitched sound range, can be perceived and external sounds can also be heard. Therefore, the user can hear reproduced sound of music and the like while playing sports outdoors or taking a walk. Since, at this time, he can hear somebody calling him or the sound of the car horn, he can use the headphone with safety.

The headphone of the present embodiment can also be used as a general closed type headphone by using it with the window hole <b>28</b> closed by shutting it with the lid member <b>32</b>. In this case, attenuation of the sound in the low-pitched sound range does not become so great and totally well-balanced sound can be heard, while the external sound is scarcely heard. Therefore, the listener can personally enjoy a reproduced sound at home not disturbed by the external sound.

When the headphone is used in a train or bus, a sound leaking out of the headphone is annoying to other passengers. At such an occasion, if the present headphone is used as a closed-type headphone, the sound from the headphone hardly leaks out and, hence, other passengers are not annoyed by a leaking sound. Thus, the present headphone can be easily changed to the closed-type headphone according to the need.

FIG. 8 is a diagram, corresponding to FIG. 4, showing a second embodiment of the invention. In FIG. 8, a second diaphragm <b>30</b> is provided at the portion of the baffle plate <b>19</b>, where the through hole <b>21</b> and acoustic resistance member <b>22</b> were provided in FIG. 4, and a window hole <b>28</b>, together with a removable lid member <b>32</b>, is formed at the portion of the housing <b>29</b> confronted with the rear side of the second diaphragm <b>30</b>. Also from this second embodiment, characteristics similar to those obtained from the first embodiment could be obtained.