Technical Field The present invention relates to an apparatus for converting a sound signal into vibration so as to stimulate the human auditory organs through the human bones. More particularly, this invention relates to an apparatus producing high power vibration energy by simply remodeling a conventional loudspeaker employing a voice coil and a permanent magnet.

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. A bone-conducting loudspeaker for auditorily handicapped persons is disclosed in a Korean patent application No. 1994-25746 (filing date is 7 October 1994).

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, the body-sensible loudspeaker is generally sold at a high price because of its complicated structure.

Disclosure of Invention To solve the above disadvantages in conventional body-sensible loudspeakers, it is an object of the present invention to provide a simple body-sensible loudspeaker apparatus producing high power vibration energy by simply remodeling a conventional acoustic loudspeaker.

A sound-to-vibration conversion apparatus of this invention comprises a conical housing having an apex portion; a permanent magnet fixed to an apex portion of the conical housing; a voice coil facing the permanent magnet, the voice coil reciprocating to get close to and away from the permanent magnet according to the interaction between the polarity of the coil produced by an acoustic signal from an audio system and the polarity of the permanent magnet; a conical diaphragm whose apex portion is fixed to the voice coil and a mouth portion is fixed to the conical housing, the diaphragm vibrating against the housing along with the voice coil ; an inertial mass included in the conical diaphragm, so as to increase the inertial force of the voice coil's reciprocal motion, such that the housing including the permanent magnet can vibrate against the voice coil.

It is desirable that the above-organized apparatus further comprises an upper limit stopper and a lower limit stopper for limiting the conical diaphragm's reciprocating distance, the upper limit stopper being located at a mouth portion of the conical housing, the lower limit stopper being located between the voice coil and the permanent magnet.

It is also desirable that the above-organized apparatus further comprises a first

damper interposed between a mouth portion of the diaphragm and a mouth portion of the housing, and a second damper interposed between an apex portion, where the voice coil is attached, of the diaphragm and the neighboring housing portion, the first and second dampers mechanically separating the cone diaphragm, the voice coil, and the housing from each other, so that they can freely vibrate, respectively.

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 drawing, in which: FIG. 1 is a structural diagram showing the present invention, a sound-to-vibration conversion apparatus.

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

With reference to FIG. 1, a sound-to-vibration conversion apparatus according to the present invention is composed of a conical housing 13 having an apex portion; a permanent magnet 15 fixed to an apex portion of the conical housing 13 ; a voice coil 17 facing the permanent magnet 15, the voice coil 17 reciprocating to get close to and away from the permanent magnet 15 according to the interaction between the polarity of the coil 17 produced by an alternate current (acoustic signal from an audio system) and the polarity of the permanent magnet 15; a conical diaphragm 19 whose apex portion is fixed to the voice coil 17 and mouth part is fixed to the conical housing 13, the diaphragm 19 vibrating

against the housing 13 along with the voice coil 17; an inertial mass included in the conical diaphragm 19, so as to increase the inertial force of the voice coil's reciprocal motion, such that the housing 13 including the permanent magnet 15 can vibrate against the voice coil 17.

In the above, the permanent magnet 15, which is fixed to an apex portion of the housing 13, is secured in a squared-U shaped yoke 11. The conical diaphragm 19 may be made of durable paper. Rather, in the present invention, it is possible to make the conical diaphragm 19 out of metal or plastics, because the diaphragm 19 does not directly produce sound in this invention. The inertial mass 21 may be made from lead (Pb), because lead is relatively heavy for its volume.

In addition to the above configuration, a sound-to-vibration conversion apparatus of this invention may comprise an upper limit stopper and a lower limit stopper to limit the conical diaphragm's reciprocating distance. The upper limit stopper is realized by a protrusion 23 located at a mouth portion of the conical housing 13, which stops the voice coil 17 so as not to depart over a certain distance from the permanent magnet 15. The lower limit stopper is realized by a buffer pad 25, which prevents the voice coil 17 from touching the permanent magnet 15.

A first damper 27a is interposed between a mouth portion of the diaphragm 19 and a mouth portion of the housing 13. A second damper 27b is interposed between an apex portion, where the voice coil 17 is attached, of the diaphragm 19 and the neighboring housing portion 13. Because the first and second dampers 27a and 27b mechanically separates the cone diaphragm 19, the voice coil 17, and the housing 13 from each other, they 19,17,23 can freely vibrate, respectively. It is preferable that the damper 27a, 27b should be made of the material, such as metal or epoxies, sturdier than the conventional loudspeaker, to avoid vibration damage from the heavy inertial mass 21.

From the above configuration, it can be noted that the voice coil 17 reciprocates in such directions to get close to or away from the permanent magnet 15, in accordance with the interaction between the polarities formed at the voice coil 17 by the acoustic signal and at the permanent magnet 15. That is to say, when an acoustic signal is applied to the voice coil 17, the polarity and the magnetic force of the voice coil 15 varies according to the applied acoustic signal's amplitude or phase. Thereby, the attractive force and repulsive force between the voice coil 13 and the permanent magnet 15 causes the voice coil 17 to reciprocate, and so the conical diaphragm 19 to vibrate.

Meanwhile, because the voice coil 17 includes an inertial mass 21 to increase the inertial force of the diaphragm's reciprocal or vibratory motion. Therefore, the housing 13 including the permanent magnet 15 will vibrate instead of the voice coil 17. Accordingly, the vibration energy of a sound-to-vibration conversion apparatus of the present invention can be much more augmented. When the housing 13 vibrates, this vibration energy is transferred to a seat, a bed, a chair, etc. (not shown) to which the housing 13 is equipped and finally the vibration energy will be transmitted to stimulate the human tactile organs.

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.

Returning to FIG. 1, an exhaust port 29 may be formed at the permanent magnet 15 and the yoke 11. Similar to a syringe or cylinder-piston, when the voice coil 17 gets close to the permanent magnet 15, the air in the space formed by the voice coil 17 and the permanent magnet 15 is compressed. Thus, the exhaust port 29 is added to exhaust the air compressed by the voice coil 17 and the permanent magnet 15.

According to the present invention, as well as the housing's vibration, the conical diaphragm 19 can vibrate to produce acoustic sound, like the conventional acoustic loudspeaker. However, from the sound wave generated by this invention, only high-tone components can be acoustically regenerated because of the heavy inertial mass 21, and so amplitude reduction in mid-and low-tone bands will arise. Therefore, when adapting the sound-to-vibration conversion apparatus of this invention for vehicle use to get acoustic sound as well as vibration, it is desirable to additionally equip a mid-and low-tone dedicated loudspeaker, i. e., a woofer or subwoofer.

If the sound-to-vibration conversion apparatus according to the present invention is installed in a car door, the door will play a role of resonance chamber, and thus very soft bass tone can be obtain. This apparatus may also be adapted in an electric piano. In these cases, as described above, it is recommended that an amplifier for providing acoustic signal to the apparatus of this invention should include a frequency trap, because the car door or piano body may abnormally resonate in response to a particular frequency.

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 electric 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.