Background Art Conventionally, a bone-conducting loudspeaker has been developed for persons who have difficulty in hearing. This loudspeaker is a kind of acoustic transducer that enables an auditorily handicapped person who does not have the tympanic membrane to hear by stimulating the auditory nerves through the cranial bone instead of the tympanic membrane.

Basically, the bone-conducting loudspeaker produces sound through the medium of liquid or solid matters, such as the human body, while the conventional loudspeaker uses the atmosphere.

FIG. 1 is a structural diagram roughly showing the conventional acoustic loudspeaker.

As shown, a permanent magnet 3 is fixed to a conical frame 1. One pole of the magnet 3 is inserted in a cylindrical electromagnet 7 around which a voice coil 5 is wound and which has a closed face. To the closed face of the electromagnet 7, a conical vibrating diaphragm 9 is attached. This diaphragm 9 vibrates back and forth (in the direction of Y in FIG. 1) along with the electromagnet 7. More specifically speaking, when an acoustic signal V is applied to the voice coil 5, the coil 5 produces magnetic force. The magnetic force interacts

with the magnet 3 to move the electromagnet 7. Thereby the diaphragm 9 vibrates and regenerates acoustic sound by waving the surrounding atmosphere.

Meanwhile, in order to expand the purpose of hearing aid for auditorily handicapped persons, a"body-sensible loudspeaker"has been developed, by which a user can sense the acoustic energy generated from an audio system, through the tactile organs rather than the auditory organs. The body-sensible loudspeaker, which converts the acoustic signal into vibration to stimulate the human body, provides even more vivid sound in comparison with the conventional acoustic loudspeaker. It can be used for vehicle seats, game tools, theatre seats, etc.

However, in the conventional body-sensible loudspeaker, high power output cannot be obtained because it directly uses a structure of the conventional acoustic loudspeaker (see FIG. 1). In the conventional acoustic loudspeaker, vibrating diaphragm is made of soft materials, such as paper or PVC. Thus, it has a disadvantage that: A coil becomes short-lived because of heat generated by the amount of current increasing when the output power is made higher. Moreover, if the fundamental oscillation frequency of the vibrating diaphragm coincides with the frequency of the amplified acoustic signal, the diaphragm may resonate. This will cause the diaphragm to abnormally oscillate, thereby, the frequency over a certain frequency value being blocked.

Disclosure of Invention To solve the above disadvantages in conventional body-sensible loudspeakers, it is an object of the present invention to provide a new-organized loudspeaker for increasing vibration energy by using an electromagnet having an ironcore and an inertial mass.

To achieve the above object, there is provided a sound-to-vibration conversion

apparatus comprising a housing; a magnet means having N-and S-pole, only one of N-and S-pole being fixed to the housing; and an electromagnet movably fixed to the housing so as to face N-or S-pole, not fixed to the housing, of the magnet means, whereby the electromagnet reciprocates in such directions to get close to or away from the magnet means in accordance with the interaction between the polarity formed at the electromagnet by the acoustic signal applied to the electromagnet and either N-or S-pole of the magnet means.

In the above, the electromagnet includes an E-shaped iron core having three protrusions; and a coil wound around a central protrusion.

It is desirable that the electromagnet comprises an inertial mass for increasing inertial force of the electromagnet's reciprocal motion, such that the housing including the magnet means can vibrate against the electromagnet. It is also desirable that the magnet means is a permanent magnet. And it is also desirable that the apparatus according to this invention further comprises an elastic means for giving the electromagnet a resisting power in the opposite directions of the electromagnet's motion, and a spacer for keeping apart the electromagnet from the permanent magnet even when the electromagnet approaches nearest to the magnet means.

Brief Description of Drawings The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which: FIG. 1 is a structural diagram roughly showing the conventional acoustic loudspeaker, and FIG. 2 is a cross-sectional view showing a preferred embodiment for carrying out the

present invention.

Preferred Embodiment for Carrying out the Invention Preferred embodiment will be described herein below with reference to the accompanying drawings.

FIG. 2 is a cross-sectional view showing the preferred embodiment of the present invention. A sound-to-vibration conversion apparatus according to the present invention is roughly composed of a magnet means 11 having N-pole and S-pole and being fixed to a housing 23, and an electromagnet 13 arranged to face N-or S-pole of the magnet means 11 and movably fixed to the housing 23. (Even though FIG. 2 shows that the electromagnet 13 faces N-pole of the magnet means 11, this is not limited to such a situation.) The housing 23 may be a car seat, a bed, a chair, or any other things that this apparatus could be adapted. Even though the magnet means 11 can include either a permanent magnet or an electromagnet, in this description a permanent magnet will be typically referred to for convenience.

As shown in FIG. 2, the electromagnets 13 includes an E-shaped iron core having three protrusions 13a, b, c; and a coil 15 wound around a central protrusion 13a. To the coil 15, alternate current (acoustic signal from an audio system) is applied.

From the above configuration, it can be noted that the electromagnet 13 reciprocates in such directions to get close to or away from the magnet means 11, in accordance with the interaction between the polarities formed at the electromagnet 13 by the acoustic signal applied to a coil 15 and at the magnet means 11. That is to say, when an acoustic signal is applied to the coil 15, the polarity and the magnetic force of the electromagnet 13 varies according to the applied acoustic signal's amplitude or phase. Thereby, the attractive force

and repulsive force between the electromagnet 13 and the permanent magnet 11 causes the electromagnet 13 to reciprocate. Here, the reciprocating distance of the electromagnet 13 traces a waveform of the applied acoustic signals.

From the foregoing, a sound-to-vibration conversion apparatus of the present invention utilizes magnetic force to convert sound into vibration, like the conventional acoustic loudspeaker. Therefore, it is necessary to adapt a magnet and a coil to this invention also. However, unlike the conventional body-sensible loudspeaker, this invention employs an iron-cored electromagnet 13 that a coil is wound around an iron core. Because the iron-cored electromagnet 13 is relatively heavy, it acts as an inertial mass against the fixed magnet 11, so that the interaction between the fixed magnet 11 and the electromagnet 13 can produce much more vivid vibration. Additionally, because an iron-cored electromagnet 13 provides higher efficiency than a non-iron-cored electromagnet, the loss of magnetic force becomes lesser in this invention.

Meanwhile, the electromagnet 13 includes an inertial mass 17 to increase the inertial force of the electromagnet's reciprocal motion. Therefore, even though the electromagnet 13 is movably fixed to the housing 23, because the electromagnet 13 including the inertial mass 17 is heavier than the housing 23, the housing 23 including the permanent magnet 11 will vibrate instead of the electromagnet 13. Accordingly, the vibration energy of a sound- to-vibration conversion apparatus of the present invention can be much more augmented.

When the housing 23 vibrates, this vibration energy is transferred to a seat, a bed, a chair, etc. (not shown) to which the housing 23 is attached, and finally the vibration energy will be transmitted to stimulate the human tactile organs.

Returning to FIG. 2, the reference numerals"19a"and"19b"denote elastic members for giving the electromagnet the resisting force in the opposite directions of the

electromagnet's motion. And the reference numeral"21"denotes a spacer for keeping apart the electromagnet 13 from the permanent magnet 11 and for shock-absorbing when the housing 23 including the permanent magnet 11 collides with the electromagnet 13.

As described above, when the housing 23 vibrates or collides with the electromagnet 13, a user can sense the strong vibration from this apparatus. This invention provides a user with a strong and vivid explosive sound and explosive vibration when used in a computer game station or a theater seat.

In the mean time, it is desirable to include a frequency trap in an amplifier for providing acoustic signal to the apparatus of this invention, because the electromagnet may abnormally oscillate in response to a particular frequency. A frequency trap for this aim is well known to an ordinary person who is skilled in the art to which this invention pertains.

Unexplained element"25"denotes a frame for supporting the electromagnet 13, the elastic members 19a, b, and the inertial mass 17, which is separated from the housing 23 on which the permanent magnet 11 is fixed and that is attached to a seat or a chair, etc.

From the foregoing, the sound-to-vibration conversion apparatus according to the present invention has an advantage of providing high power vibration energy with lower heat consumption. loss. Moreover, its simple structure makes it possible to improve the productivity with chief cost. This apparatus can be used for seats of vehicles to satisfy the audio or car maniacs'desire. If it is used for a computer, a game machine, a theater chair, a floor, a ceiling, a wall, etc., a user can enjoy vivid and intense sound as if he were in the spot. If it is used for a mattress or bed, it is helpful to antenatal training of pregnant women, curing insomnia, and promoting a dramatic married life.

If the sound-to-vibration conversion apparatus of the present invention is adapted to keyboards of an electronic piano, since fingers can feel the vibration through the keyboards,

even auditorily handicapped persons can play the piano as they are feeling the tones. This invention may be applied to an acoustic resonator apparatus. That is, this invention can reduce vehicle or toilet noise, and, if it attached to a conference room or window, eavesdrop can be prevented. Besides, this invention is applicable to communication means using the medium of liquid or solid, and to a massage treatment machine.

While the invention has been shown and described with reference to a certain embodiment to carry out this invention, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.