Sound output device comprises a dual speaker including a dynamic speaker and a piezoelectric speaker

Provided is a sound output apparatus including: a housing having a housing space therein; a first sound output unit provided inside the housing; and a second sound output unit provided in the housing and spaced a predetermined distance from the first sound output unit.

BACKGROUND

The present disclosure relates to a sound output apparatus, and more particularly, to a sound output apparatus capable of enhancing output characteristics in audible frequency bands including low-frequency bands and high-frequency bands.

In general, a piezoelectric device refers to a device having a characteristic capable of mutually changing electrical energy to/from mechanical energy. That is, an electric voltage is generated when a pressure is applied on the piezoelectric device (the piezoelectric effect), and an increase or decrease in volume or length due to an internal pressure change occurs when the electric voltage is applied thereto (the inverse piezoelectric effect). The piezoelectric device is configured with a piezoelectric layer and an electrode provided thereon, and a pressure thereof changes according to the electrical voltage applied to the piezoelectric layer through the electrode.

Various components such as a piezoelectric speaker, a vibration apparatus, or the like may be manufactured using the piezoelectric device. Among these, the piezoelectric speaker is a component which acoustically converts mechanical movements of the piezoelectric device into a sound in desired frequency bands using a vibration plate. It is advantageous that the piezoelectric speaker is thinner and lighter, and smaller in power consumption than an existing dynamic speaker, and thus the piezoelectric speaker can be used in electronic apparatuses such as smart phones which are required to be small, thin, and light-weighted. However, the piezoelectric speaker is disadvantageous in that the piezoelectric speaker delivers strong high-pitched sound and weak low-pitched sound, which causes a user to be unable to listen to music for a long time.

Meanwhile, dynamic speakers are widely used for music playback. The dynamic speakers use the principle that when an audio signal current is applied to a voice coil placed within the magnetic field of a magnet, a mechanical force acts on the voice coil according to the intensity of the current, and thus a movement is caused. However, the dynamic speakers are suitable for implementing low-frequency sound, but are relatively poor for implementing high-frequency sound, and thus the dynamic speakers have limitations in providing high sound quality.

RELATED ART DOCUMENTS

SUMMARY

The present disclosure provides a sound output apparatus capable of having both the advantages of a piezoelectric speaker and the advantages of a dynamic speaker.

The present disclosure also provides a sound output apparatus capable of improving both low-frequency sound characteristics and high-frequency sound characteristics.

In accordance with an exemplary embodiment, a sound output apparatus may include: a housing having a housing space therein; a first sound output unit provided inside the housing; and a second sound output unit provided inside the housing spaced apart by a predetermined distance from the first sound output.

The sound output apparatus may include at least one emission hole formed in a predetermined region of the housing.

The first sound output unit includes a dynamic speaker, and the second sound output unit includes a piezoelectric speaker.

A separation space may be provided between the first and second sound output units, and the emission hole is formed such that at least a portion of the emission hole corresponds to the separation space.

The housing may include a first member, and a second member provided to surround the first member, and the emission hole may be formed in a predetermined region of the second member.

The first member may be provided in a plate shape having a predetermined thickness, and may separate the first and second sound output units from each other.

A stepped portion may be formed on at least one region of one surface of the first member.

The second sound output unit may be provided to contact the stepped portion of the first member, and the first sound output unit may be provided spaced from the other surface opposite to the one surface.

The sound output apparatus may further include at least one protrusion protruding from the inner portion of the second member.

The first member may be provided on an upper portion of the protrusion, and the first sound output unit may be in contact with a lower portion of the protrusion.

The emission hole may be formed to correspond to a space between the first member and the first sound output unit.

The emission hole may be formed to have an area of about 5% to about 90% of the to surface area of the first sound output unit.

The sound output apparatus may further include a coating layer formed on at least a portion of at least one of the first and second sound output units, or the housing.

The first and second sound output units may be driven at the same time by a signal having the same level.

The first and second output units may be driven in a voltage range of about 0.1V to about 5.0V.

The second sound output unit may include a vibration device having an opening, and a piezoelectric device provided on at least one surface over the opening of the vibration device.

A sound output from the second sound output unit may be output through the first sound output unit, and a sound emitted through the emission hole may be mixed outside the housing with the sound output from the first sound output unit.

In accordance with another exemplary embodiment, a sound output apparatus may include: a housing having a housing space therein; a first sound output unit provided inside the housing; a second sound output unit provided inside the housing spaced a predetermined space from the first sound output unit; and a separation member provided between the first and second sound output units inside the housing and to separate the first and second sound output units from each other.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1is an exploded view illustrating a sound output apparatus in accordance with an exemplary embodiment of the present disclosure;FIG. 2is a combined perspective view of the sound output apparatus; andFIG. 3is a combined cross-sectional view of the sound output apparatus.

Referring toFIGS. 1, 2, and 3, the sound output apparatus in accordance with an exemplary embodiment of the present disclosure may include a first sound output unit100, a second sound output unit200provided on the first sound output unit100, and a housing300for housing the first and second sound output units100and200. That is, the first and second sound output units100and200may be provided inside the housing300such that the first and second sound output units100and200are spaced apart by a predetermined distance from each other. The first sound output unit100may include a dynamic speaker which includes a voice coil140and a vibration plate150, and outputs sound by vibrating the vibration plate150using vibration caused by current change in the voice coil140. Also, the second sound output unit200may include a piezoelectric speaker which includes a piezoelectric device210and a vibration device220and acoustically converts a mechanical movement of the piezoelectric device210into a sound by the vibration device220.

1. First Sound Output Unit

The first sound output unit100may be provided in a substantially circular shape having a predetermined thickness. The first sound output unit100may include: a yoke110and a frame115which define a housing space therein; a magnet120provided in the housing space inside the yoke110; a plate130provided on the magnet120; a voice coil140spaced from the inner portion of the frame115and disposed between the yoke110and the magnet120; and a vibration plate150which is provided above the plate130, an edge of which is fixed to the frame115, and to which the voice coil140is fixed.

The yoke110is provided in a substantially cylindrical shape having a predetermined height, and the frame115is provided to an upper section of the yoke110and has a substantially cylindrical shape having a predetermined height. The height of the frame115may be greater than that of the yoke110, and the width of the frame115may be greater than that of the yoke110. The height of the frame115may be equal to or lower than the height of the yoke110. An upper edge of the frame115is in contact with at least a portion of the housing300, and may be housed in the housing300. Also, the magnet120and the plate130are housed inside the yoke110, the voice coil140is housed inside the frame115, and the vibration plate150may be provided on the frame115so as to cover the same. The yoke110and the frame115induce a magnetic field generated by the magnet120towards the plate130and apply the magnetic force by the magnet120to the voice coil140to the maximum.

The magnet120is fixed to a bottom surface of the yoke110. That is, the undersurface of the magnet120is in contact with and fixed to the bottom surface of the yoke110. The magnet120may be provided in a shape corresponding to the internal shape of the yoke110. For example, the internal shape of the yoke110has a substantially cylindrical bucket shape, and the magnet120has a substantially cylindrical shape. The height of the magnet120may be the lower than or equal to the height of the yoke110. Also, the diameter of the magnet120may be smaller than the inner diameter of the yoke110. Thus, the magnet120may be provided inside the yoke110such that the magnet120is spaced apart by a predetermined distance from the inner sidewall of the yoke110.

The plate130is provided on the top surface of the magnet120. The plate130may be provided in a shape similar to the planar shape of the magnet120. That is, the plate130may be provided in a circular plate shape having a predetermined thickness. The plate130has a smaller diameter than the inner diameter of the yoke110, and may have a diameter equal to or larger than the diameter of the magnet120. Thus, an outer portion of the magnet120may be spaced part by a predetermined distance from the inner side surface of the yoke110. Also, the total height of the magnet120and the plate130provided on the magnet120may be the same as the height of the yoke110. That is, top portions of the plate130and the yoke may be coplanar with each other. The plate130allows lines of magnetic force generated by the magnet120to be focused towards the voice coil140.

The voice coil140is attached to the undersurface of the vibration plate150, and may be spaced from the frame115and provided between the yoke110and the magnet120. For example, the voice coil140is provided between the yoke110and the magnet120so as to surround the plate130and a portion of the magnet120with a predetermined height, and has an upper portion attached to the undersurface of the vibration plate150. The voice coil140forms a magnetic field which consistently changes by an electrical signal that is input while consistently changing, and therefore the voice coil140vibrates by an interaction due to interference between the magnetic field and another magnetic field formed by the magnet120.

An edge of the vibration plate150is fixed to an inner portion of the frame115such that the vibration plate150is provided to cover an upper portion of the frame115. In the vibration plate150, at least a portion thereof may be convexly provided. For example, the vibration plate150may be provided in such a shape that the vibration plate150has the highest portion corresponding to a central portion of the plate115, and a peripheral portion gradually lowered from the center portion to the outside. Also, the voice coil140may be fixed to the undersurface the lowest portion of the vibration plate150.

The first sound output unit100constitutes a closed circuit in which the magnetic filed generated from the magnet120moves to the yoke110positioned at a lower side through the plate130provided on the magnet120, and moves back to the magnet120. The magnetic field moving into a space between the plate130and the yoke110thereunder pushes or pulls the voice coil140according to a magnetic polarity of the voice coil140when the voice coil140is magnetized by a current applied thereto. That is, the voice coil140is pushed out by a mutual repulsion and moved forward when the voice coil140has the same magnetic polarity as the plate130and the yoke110thereunder, and the voice coil140is attracted and pulled back when the voice coil140has a different magnetic polarity from the plate130and the yoke110thereunder. In this way, when the voice coil140moves, the vibration plate150to which the voice coil140is fixed reciprocates and vibrates air, and generates a sound.

2. Second Sound Output Unit

The second sound output unit200may include a piezoelectric device210and a vibration device220. The piezoelectric device210may be provided, for example, in a circular plate shape having a predetermined thickness. Alternatively, the piezoelectric device210may also be provided in various shapes such as a square, a rectangular, an oval, a polygonal shape or the like as well as a circular shape. The piezoelectric device210may include a substrate and a piezoelectric layer on which the substrate is formed on at least one surface thereof. For example, the piezoelectric device210may be formed as a bimorph type device in which the piezoelectric layers are formed on both sides of the substrate, or formed as a unimorph type device in which the piezoelectric layer is formed on one surface of the substrate. At least one piezoelectric layer may be laminated, and a plurality of piezoelectric layers may be preferably laminated. Also, electrodes may be respectively formed over and below the piezoelectric layer. That is, a plurality of piezoelectric layers and a plurality of electrodes may be alternately laminated to form the piezoelectric device210. The piezoelectric layer may be formed using for example, PZT (Pb, Zr, Ti), NKN (Na, K, Nb), BNT (Bi, Na, Ti), or a polymer-based piezoelectric material. Also, the piezoelectric layers may be laminated such that the piezoelectric layers are polarized in different or same orientation. That is, when a plurality of piezoelectric layers is formed on the same surface of a substrate, the piezoelectric layers may have polarizations that are alternated in a different or same orientation. Meanwhile, the substrate may use a material having a characteristic that vibration may occur while maintaining a laminated structure of the piezoelectric layers, for example, may be formed of metal, plastics and the like. However, the piezoelectric device210may not use the piezoelectric layer or the substrate, for example, the piezoelectric device210may be formed in such a configuration that an unpolarized piezoelectric layer is provided in the central portion thereof, and a plurality of piezoelectric layers polarized in different orientations are laminated over and below the unpolarized piezoelectric layer. Meanwhile, an electrode pattern (not illustrated) to which a driving signal is applied may be formed on one surface of the piezoelectric device210. At least two electrode patterns may be formed spaced apart from each other, and connected with connection terminals (not illustrated), thereby receiving a sound signal from electronic apparatuses, such as auxiliary mobile apparatuses.

The vibration device220is provided in a substantially circular shape, and may be bigger than the piezoelectric device210. Also, the vibration device220may have an opening formed in center portion thereof, and the piezoelectric device210may be provided over the opening. The piezoelectric device210may be bonded to the top surface of the vibration device220by adhesives. The vibration device220may use a polymer- or pulp-based material. For example, the vibration device220may use a resin film such as an ethylene propylene rubber-based material, a styrene butadiene rubber-based material, and the like having a high loss factor, in which Young's modulus is in a range from about 1 MPa to 10 GPa. Also, a lower edge of the vibration device220may contact an inner surface of the housing300. That is, the vibration device220and the piezoelectric device210bonded to the center portion of the vibration device220may be provided inside the housing300. The second sound output unit200is driven by a predetermined signal, and may output a sound having excellent high-frequency sound characteristics.

Meanwhile, a coating layer (not illustrated) may be further formed on at least a portion of the second sound output unit200. The coating layer may be formed using waterproof materials such as parylene. The parylene may be formed on the upper and side surfaces of the piezoelectric device210and the upper and side surfaces of the vibration device220exposed by the piezoelectric device210, in a state in which the piezoelectric device210is bonded onto the vibration device220. That is, the parylene may be formed on the upper and side surfaces of the piezoelectric device210and the vibration device220. Also, the parylene may be formed on the upper and side surfaces of the piezoelectric device210and the top, side, and bottom surfaces of the vibration device220, in a state in which the piezoelectric device210is bonded onto the vibration device220. That is, the parylene may be formed on the top, side, and bottom surfaces of the piezoelectric device210and the vibration device220. When the piezoelectric device210is provided over the opening formed in the center portion of the of the vibration device220, the parylene is formed on the top and side surfaces, and the bottom surface exposed by the opening, and may also be formed on the top, side, and bottom surfaces of the vibration device220. As such, since the parylene is formed on at least one surface of each of the piezoelectric device210and the vibration device220, moisture penetration into the second sound output unit200and a oxidation phenomenon may be prevented. Furthermore, a horizontal vibration caused by use of the vibration device220made of a thin material such as polymer may be mitigated, a response speed is enhanced by an increase in hardness of the vibration device220, and thus an in-depth acoustic characteristic is mitigated, and a high-frequency band sound may be stabilized. Since a resonant frequency may be adjusted in accordance with the coating thickness of the parylene, a sound pressure improvement point may is possibly adjusted. While the parylene may also be coated on the piezoelectric device210only, the parylene may be coated on the top, side, and bottom surfaces of the piezoelectric device210, and may also be coated on an FPCB which is connected to the piezoelectric device210for supplying power to the piezoelectric device210. As the parylene is coated on the piezoelectric device210, the moisture penetration into the piezoelectric device and the oxidation may be prevented. Also, the resonant frequency may be adjusted by adjusting a forming thickness. Meanwhile, when the parylene is formed on the FPCB, a noise generated by the FPCB and solder, and a device connecting part may also be mitigated. The parylene may be coated in different thicknesses in accordance with materials and characteristics of the piezoelectric device210or the vibration device220. The parylene may be formed thinner than the piezoelectric device210or the vibration device220, and may be, for example, formed in a thickness of about 0.1 μm to about 10 μm. For example, the parylene may be coated on at least one surface of the second sound output unit200by vaporizing parylene through a primary heating in a vaporizer to be turned into a dimmer state, then pyrolyzing the resultant into a monomer state through a secondary heating, and converting the resultant into a polymer state from the monomer state by cooling the parylene. Meanwhile, a waterproof layer such as the parylene or the like may also be coated on at least a portion of the first sound output unit100and the housing200as well as at least on a portion of the second sound output unit200.

The housing300is provided in a substantially cylindrical shape in which at least a portion of a side surface thereof is removed. That is, the housing300is provided in a tubular shape vertically opened, and may be provided in the shape in which at least a portion of the side surface is removed. For example, the housing300may also be provided as a vertical penetration type one, and also has a shape in which a predetermined inner region is closed and the upper and bottom portions thereof are opened therefrom. The vertical penetration type housing300may include a first member310having a substantially ring shape having a predetermined thickness, and at least one second member320provided in upward and downward direction from a predetermined region of the first member310. That is, the second member320may be provided to surround the ring-shaped first member310. Alternatively, when the first member310is provided in a circular plate shape, the housing300may be implemented in a shape in which the upper and lower portions thereof are opened from the first member310. Also, the second member320may be provided outside the first member310such that the second member320is spaced apart by a predetermined distance from the first member310. For example, the second member320having a predetermined width may be provided in four and the four second members320are spaced apart by a predetermined distance from each other. The distance between the second members320may be the same as or smaller than the width of the second member320. For example, the distance between the second members320may be about 10% to about 100% of the width of the second member320. In this exemplary embodiment, the second member320is illustrated to have the same thickness as the distance between the second members320. That is, the second member320having a predetermined width may be provided in plurality by being spaced apart by the same distance as the width thereof. Meanwhile, a protrusion321may be provided inside the second member320. That is, the protrusion321may be provided to inwardly protrude from an inner wall of the second member320. Also, the first member310may be seated on the protrusion321. The first and second members310and320may be manufactured separately and thereafter the first member310is seated on the protrusion321of the second member320. Alternatively, the first and second members310and320may be manufactured integrally. Also, the first and second members310and320may be manufactured without providing the protrusion321such that an outer portion of the first member310is attached to be in contact with an inner portion of the second member320, or manufactured integrally. In the housing300, the second sound output unit200, i.e., the vibration device220of the piezoelectric speaker, may contact the top surface of the first member310, and the first sound output unit100, i.e., a dynamic speaker, may contact a lower portion of the protrusion321of the second member320. That is, the first and second sound output units100and200may be provided spaced apart by a predetermined distance from each other with the first member310and the protrusion321disposed therebetween. When the first member310is in contact with the inner wall of the second member320without the protrusion321provided to the inner portion of the second member320, the vibration device220may be in contact with the top surface of the ring-shaped first member310, the first sound output unit100may be in contact with the bottom surface of the first member310. That is, the first and second sound output units100and200may be opposed to each other by being spaced apart by the thickness of the first member210from each other. Also, the first and second sound output units100and200are spaced apart by a predetermined distance from each other, and at least a portion of a region between the second members320may function as an emission hole330. That is, the first sound output unit100and the first member310are spaced apart by a predetermined distance from each other, and the emission hole330may be provided to correspond to the space therebetween. The emission hole330may be formed in a size of about 5% to about 90% of the top surface area of the first sound output unit100. That is, the emission hole330may be provided by at least one or more, and the whole area of the emission holes330may be formed in a size of about 5% to about 90% of the top surface area of the first sound output unit100, i.e. the area of the vibration plate150. The size of the emission holes330may be preferably formed in a size of about 10% to 60%, and more preferably in a size of about 15% to 30% of the top surface area of the first sound output unit100. A sound from the first sound output unit100is emitted through the emission hole330. Thus, the sound from the second sound output unit200is directly emitted to the outside, and the sound from the first sound output unit100is emitted through the emission hole330of the housing300, and thus the two sounds are mixed outside the housing300thereby further improving a sound quality. Meanwhile, the sound output apparatus may be manufactured for a speaker for vehicle speakers, in-house speakers, or the like, or as amplifiers and earphones. When the sound output apparatus is manufactured as the earphone such as a kernel-type earphone, the housing300may be manufactured in a substantial size that may be inserted in an ear. The earphone may be inserted in an ear from the second output unit200. Thus, the sound from the second sound output unit200is firstly output and the sound from the first sound output unit100is later output, so that the two sounds are then mixed inside the ear. Alternatively, the first sound output unit100may be firstly inserted in the ear, and the two sounds will also be then mixed inside the ear. Also, according to exemplary embodiments of the present disclosure, the sound output apparatus may be manufactured by inserting the first and second sound output units100and200in the housing so as to be spaced from each other, or may also be manufactured by combining a portion of the housing300in which the first sound output unit100is inserted, with another portion of the housing300in which the second sound output unit200is inserted. For example, the sound output apparatus may be manufactured such that the thickness of the first member310is divided in half, the first sound output unit100is then inserted inside a first housing with a portion of the second member320formed such that the emission hole330is formed to surround a first-thickness lower portion of the first member310, the second sound output unit200is then inserted inside a second housing with a portion of the second member320formed to surround a second-thickness upper portion of the first member310, and thereafter the first and second housings are combined. Meanwhile, the sound output apparatus in accordance with the present disclosure can be driven in a low voltage range of about 0.1V to 5.0V, preferably of about 0.1V to about 2.0V, and more preferably of about 0.1V to about 0.5V. Particularly, when the same is applied to the earphones, the sound output apparatus can be driven in a low voltage range of about 0.1V to about 0.2V, and preferably of about 0.1V to about 0.18V. That is, in the piezoelectric device210of the second sound output unit200, a plurality of piezoelectric layers is laminated, and internal electrodes are formed between the respective piezoelectric layers. Here, since the piezoelectric layer is formed in a thickness ranging from about 5 μm to about 20 μm, the second sound output unit200can be driven in a low voltage range. While a driving voltage of a typical piezoelectric speaker is 5V or more, the second sound output unit200according to the present disclosure can be driven in a low voltage range of about 0.1V to about 0.5V without using an amplifier for piezoelectric speaker, and can thus be driven in a low voltage range in combination with the dynamic speaker. Also, in the sound output apparatus according to the present disclosure, the first and second sound output units100and200may be driven at the same time by the same signal applied thereto. That is, a signal supplied from a signal source is directly applied to the first sound output unit100, and applied to the second sound output unit200after passing through a high band path filter, and thus low- and high-frequency band signals may be applied to the first and second sound output units100and200respectively. However, in the present disclosure, a signal having the same level may be applied to the first and second sound output units100and200at the same time.

FIG. 4is an exploded perspective view illustrating a sound output apparatus in accordance with another exemplary embodiment of the present disclosure,FIG. 5is a combined perspective view illustrating a sound output apparatus in accordance with another exemplary embodiment and yet another exemplary embodiment of the present disclosure,FIG. 6is an exploded perspective view illustrating the sound output apparatus in accordance with yet another exemplary embodiment, andFIG. 7is a combined cross-sectional view illustrating the sound output apparatus in accordance with yet another exemplary embodiment of the present disclosure.

Referring toFIGS. 4 to 7, the sound output apparatus in accordance with another exemplary embodiment and yet another exemplary embodiment of the present disclosure may include: a first sound output unit100including a voice coil140and a vibration plate150; a second sound output unit200provided on the first sound output unit100and including a piezoelectric device210and a vibration device220; and a housing300for housing the first and second sound output units100and200. In accordance with another exemplary embodiment and yet another exemplary embodiment of the present disclosure, the second sound output unit200, i.e. a piezoelectric speaker, may be implemented such that the piezoelectric device210is provided under the vibration device220. Also, an emission hole330is formed in a predetermined region of a second member320of the housing300. As illustrated inFIG. 4, a first member310may be provided in a ring shape, and as illustrated inFIGS. 6 and 7, a first member310amay be provided in a plate shape. Also, in the plate-shaped first member310a, a height difference may be formed in a predetermined region. For example, a stepped portion may be formed along an upper edge of the first member310a, and thus the height difference may be formed. That is, the first member310amay be formed in a plate shape in which a first region having a predetermined width is formed relatively higher on an edge thereof, and a second region is formed relatively lower than the first region at inner portion of the edge. The first region may be formed in a ring shape along the edge, or may be provided in at least two sub-regions spaced apart from each other. Also, the second region of the first member310amay be provided larger than the piezoelectric device210. That is, the piezoelectric device210may be provided smaller than the vibration device220and smaller than the second region such that the piezoelectric device210is not in contact with the first region. The vibration device220of the second sound output unit200is in contact with the stepped portion of the plate-shaped first member310a, i.e., the first region, and a resonant space is provided between the second region of the first member310aand the vibration device220, so that the piezoelectric device210may be disposed therein. Also, since the first member310ais provided in a plate shape, the first member310aseparates the first and second sound output units100and200from each other. That is, the plate-shaped first member310amay serve as a separation member for separating the first and second sound output units100and200. As the first and second sound output units100and200are separated by the separation member, i.e. the plate-shaped first member310a, sounds output from the first and second sound output units100and200are output without being mixed together inside the housing300. Meanwhile, at least one second member320in which an emission hole330is formed may be provided such that the second member320surrounds the ring-shaped first member310or the plate-shaped first member310a. For example, the second member320is provided singly, and a predetermined region of the second member320is cut away in a vertical direction. A signal line for supplying a signal to the second sound output unit200may be provided to the cut-away region. The width of the second member320in the cut-away region, i.e., the distance between both ends of the second member320may be about 1% to about 5% of the width of the second member320. Also, at least one emission hole330is formed in upper portion of the second member320. The emission holes330are provided in, for example four, and the four emission holes330may be spaced apart by a predetermined distance from each other at a predetermined height on a lower portion of the first members310and310a, and may be formed to the height of the second region of the first sound output unit100. That is, at least a portion of the second region of the first sound output unit100may be exposed by the emission holes330. Also, the width of the emission hole330may be for example, about 20% to about 80%, and preferably about 50% of the width of the second member320. The area of the emission hole330may be about 5% to about 90% of the top space area of the first sound output unit100, i.e., the area of the vibration plate150. The size of the emission hole330is preferably about 10% to about 60%, and more preferably about 15% to 30% of the top surface area of the first sound output unit100. Meanwhile, when the first member310is formed in a plate shape, the first and second sound output units100and200may be spatially separated, and the sounds respectively output from the first and second sound output units100and200may be prevented from being mixed inside the housing300.

As described above, in the sound output apparatus in accordance with exemplary embodiments of the present disclosure, the first and second sound output units100and200may be provided inside the housing300, and output characteristics of both low-frequency and high-frequency sounds may be improved. That is, the first sound output unit100having excellent bass characteristics, that is the dynamic speaker, and the second sound output unit200having excellent treble characteristics, that is the piezoelectric speaker are provided inside the housing300, and thus acoustic characteristics in the audible frequency bands may be enhanced. Also, a predetermined separation space is provided between the first and second sound output units100and200inside the housing300, and the emission hole330is formed in at least a region of the housing300, and thus the sound output to the separation space from the first sound output unit100may be emitted to the outside. That is, since a sound is firstly output from the second sound output unit200and a sound is then output from the first sound output unit100through the emission hole330, the two sounds are mixed outside the housing300. Sound quality may therefore be enhanced because the two sounds are mixed outside the housing300when compared to the case in which the two sounds are mixed inside the housing300.

FIG. 8is a graph showing characteristics of a dynamic speaker, a piezoelectric speaker, and a sound output apparatus in accordance with the present disclosure. A refers to characteristics graph of the dynamic speaker, B refers to characteristics graph of the piezoelectric speaker, and C refers to characteristics graph of the sound output apparatus in accordance with an exemplary embodiment of the present disclosure in which the dynamic speaker and the piezoelectric speaker are combined inside a housing. As illustrated inFIG. 8, the dynamic speaker (A) has excellent characteristics up to about 7 kHz of audio frequency range, that is, excellent the low-frequency sound characteristics, but exhibits a phenomenon in which an attenuation of about 20 dB to 30 dB occurs at audio frequency range higher than 7 kHz when compared with the piezoelectric speaker (B). Thus, the dynamic speaker is proven to be poor in high-frequency sound characteristics. Also, the piezoelectric speaker (B) has excellent characteristics in a mid- and high-frequency band higher than 8 kHz, but exhibits a phenomenon in which the attenuation of about 30 dB or higher occurs at audio frequency range of 3 kHz or lower, which demonstrates that the piezoelectric speaker is poor in low-frequency sound characteristics. However, the sound output apparatus (C) in accordance with an exemplary embodiment of the present disclosure may be figured out that overall acoustic characteristics in the audible frequency band up to 20 kHz are excellent. That is, the sound output apparatus in accordance with the present disclosure may be proven to have similar acoustic characteristics to the dynamic speaker in an audio frequency band up to 1.5 kHz, and better acoustic characteristics than the piezoelectric speaker in the audio frequency band higher than 1.5 kHz. In an audio output apparatus in accordance with exemplary embodiments of the present disclosure, a dynamic speaker and a piezoelectric speaker are spaced a predetermined distance from each other inside a housing. Thus, acoustic characteristics in audible frequency band can be enhanced by disposing, inside a single housing, the dynamic speaker having excellent low-frequency sound characteristics and the piezoelectric speaker having excellent high-frequency sound characteristics. Also, sound quality can be further enhanced by separating the dynamic speaker and the piezoelectric speaker from each other using a separation member provided inside the housing such that the sounds separately output from the dynamic speaker and the piezoelectric speaker are not mixed inside the housing but mixed outside of the housing. Meanwhile, the sound output apparatus in accordance with exemplary embodiments of the present disclosure may be implemented as speakers, earphones, or the like.

Meanwhile, the technical idea of the present invention has been specifically described with respect to the exemplary embodiments, but it should be noted that the foregoing embodiments are provided only for illustration while not limiting the present invention. Further, it will be readily understood by those skilled in the art that various modifications and changes can be made thereto without departing from the spirit and scope of the present invention.