Abstract: An acoustic transducer may comprise a sound source, a throat connected to the sound source, and a horn connected to the throat. The horn may be arranged on a wall, wherein the throat is designed such that a path of the sound from the sound source to an interface between the throat and the horn is shorter in a region close to the wall than at a region that is remote from the wall.

Abstract: A loudspeaker including an acoustic waveguide includes an enclosure, an acoustic transmission line formed within the enclosure, and a plurality of acoustic transducers contained within the enclosure and disposed along a length of the acoustic transmission line. Each acoustic transducer is configured to emit acoustic energy directly into the acoustic transmission line at two separated locations along the length of the acoustic transmission line.

Abstract: A cover for a hand-held device, which has a device body and a speaker, includes a cover body configured for covering a portion the device body and for covering the speaker and a channel for positioning adjacent the device body. The channel is configured to form a sound duct when mounted adjacent the back side of the device body and to be in communication with the speaker when the cover is mounted to the hand-held device for redirecting at least a portion of the sound waves emitted from the speaker to a location remote from the speaker.

Abstract: Techniques described herein generally relate to generating an audio signal with a speaker. In some examples, a speaker device is described that includes a membrane and a shutter. The membrane can be configured to oscillate along a first directional path and at a first frequency effective to generate an ultrasonic acoustic signal. The shutter can be positioned about the membrane and configured to modulate the ultrasonic acoustic signal such that an audio signal can be generated.

Abstract: Apparatus and methods are disclosed for acoustic optimization. An example playback device includes a first transducer to at least one of output sound waves and receive sound waves, a second transducer to at least one of output sound waves and receive sound waves, and an acoustic grille positioned in relation to the first transducer, where the acoustic grille is to reflect sound waves received at a first angle of incidence.

Abstract: The disclosure relates to several embodiments of a concealed speaker system, The concealed speaker system further has a speaker assembly mounted to the base frame and an active member which may be formed of PVC, expanded PVC, hardened fibrous materials, foam core, or equivalents that has an outer surface which in some embodiments is substantially coplanar with the surrounding wall section, and in other embodiments extends slightly outward therefrom. The base frame, speaker assembly, and the active member cooperate to form an acoustic chamber that is positioned behind the inner surface of the active member. Acoustic energy is transferred from the speaker assembly to the active member where the sound is produced therefrom to the room.

Abstract: An acoustic horn. In one implementation, the horn includes at least four wall sections, defining a passageway. The cross-sectional area of the mouth is at least ten times the cross sectional area of the throat. The wall sections are dimensioned so that at least one wall section has a dimension at the throat at least ten times a dimension at the throat of a second wall section. In another implementation the cross-section at the mouth is elongated and is be bounded by a continuous curve defining a geometric figure having a major axis at least ten times a minor axis.

Abstract: An acoustic speaker device (10) according to the present invention comprises at least two types of gas adsorption materials in a cabinet (12) thereof. A porous carbon material package member (14A), which is one of the gas adsorption materials, can adsorb or eliminate air in the cabinet (12) by a porous carbon material (41) during the operation of a speaker unit (13) so as to buffer compression or expansion of air in the cabinet (12). A sheet-like moisture adsorbing material (14B), which is the other of the gas adsorbing materials, is formed by dispersing copper ion-exchanged ZSM-5 zeolite (43) in a thermoplastic resin composition (44), and is stuck on at least a section of an inner wall of the cabinet (12). This configuration allows moisture in the cabinet (12) to be rapidly adsorbed.

Abstract: Provided are a sound generation system and a sound recording system, which are placed in a room to adjust sound. A columnar body is disposed around a sound source to adjust how much sound of a low-tone range, as well as of a middle- and high-tone range, is absorbed and diffused. Moreover, a columnar body is disposed around a recording device to adjust how much sound of a low-tone range, as well as of a middle- and high-tone range, is absorbed and diffused. The columnar bodies may be made of a combination of different diameters and/or lengths. The arrangement distances may be random. With the columnar body disposed at the most appropriate location, it is possible to adjust sound in a wide band.

Abstract: Systems and methods (1000) for reducing a form factor of an Electronic Device (“ED”). The methods involve disposing a first user interface component (702) in a housing (710) of ED (700) such that its center axis (718) is at an angle (720) relative to a plane (722) that is perpendicular to a horizontal center axis (712) of ED. A second user interface component (704) is disposed in the housing such that its center axis (724) is parallel to the horizontal center axis of ED, and such that a top portion (734) thereof is overlapped by a bottom portion (732) of the first user interface component. A third user interface component (706) is disposed in the housing such that its center axis (726) is parallel to the horizontal center axis of ED, and such that a top portion (730) thereof overlaps a bottom portion (728) of the second user interface component.

Abstract: A loudspeaker includes a horn including a first end panel, a second end panel, a first side panel, and a second side panel. Edges of at least the first and second side panels define a diffraction slot opening. The first and second side panels are each fabricated from a sheet of flexible material held in a stressed, curved shape by at least a rigid support member. The panels are designed by an automated process based on a number of electro-acoustic transducers to be used in a loudspeaker, horizontal and vertical coverage angles for the loudspeaker, and a wall length for a horn of the loudspeaker.

Abstract: A circuit for operating loudspeakers includes a first, second, third and fourth loudspeaker circuit, having one input each for injecting a signal and one output each for connecting a loudspeaker input. The loudspeaker circuits are designed to amplify the injected signal and to provide the amplified signal at the outputs thereof. The loudspeaker circuits can, for example, be used for a 2.1 sound system. The three channels for a 2.1 sound system can be implemented by an amplifier circuit with four loudspeaker circuits, one loudspeaker circuit each being required for the two stereo channels left and right. A subwoofer channel can be driven differentially by two loudspeaker circuits. The stereo channels are, by contrast, only still connected to one loudspeaker circuit each, and so the stereo channels require at least one further common ground cable.

Abstract: An acoustical phase plug for use in loudspeakers produces a planar rectangular wavefront, or a wavefront with a desired amount of curvature, from the output aperture of the phase plug device when presented with a planar circular wavefront at the input aperture. The phase plug utilizes a waveguide that equalizes the travel paths from the input aperture to the output aperture. The waveguide essentially eliminates surface discontinuities thereby resulting in the reduction of diffraction of the wavefront travelling through the phase plug device.

Abstract: A technology which improves frequency characteristics by an acoustic method so that, when a sound-isolating earphone is attached to a human ear, the sound is heard with natural frequency characteristics is provided. In a sound path from a diaphragm of an electro-acoustic transducer inside a sound-isolating earphone to the eardrum passing through a cylindrical sound leading pipe via the external auditory canal, two independent paths for sound waves are provided in the sound leading pipe, and transfer of the sound with a specific frequency is suppressed by adjusting a difference in length of the paths, whereby the frequency characteristics of the sound passing through this sound path are improved.

Abstract: A liquid treatment system has a housing defining an interior space. The housing has an inlet port for receiving liquid into the interior space of the housing and an outlet port for allowing liquid to exit the interior space of the housing. The outlet port is spaced from the inlet port so that liquid flows through the interior space of the housing from the inlet port to the outlet port. An ultrasonic waveguide assembly is disposed within the interior space of the housing and includes an ultrasonic horn disposed at least in part intermediate the inlet port and the outlet port of the housing. The ultrasonic horn is operable at an ultrasonic frequency to ultrasonically energize liquid flowing within the housing. An ultraviolet light source emits ultraviolet light into the interior space of the housing to treat liquid flowing therein.

Abstract: An acoustic transducer comprising: a mechanical acoustic filter configured to be electrically controllable to change the acoustic properties of the transducer.

Abstract: Method, user terminal and computer program product for controlling audio signals at the user device during a communication session between the user device and a remote node, in which a primary audio signal is received at audio input means of the user device for transmission to the remote node in the communication session. It is determined whether the user device is operating in (i) a first mode in which secondary audio signals output from the user device are likely to disturb the primary audio signal received at the audio input means, or (ii) a second mode in which secondary audio signals output from the user device are not likely to disturb the primary audio signal received at the audio input means.

Abstract: The invention concerns a loudspeaker system having a plurality of segmented line array speakers and a plurality of acoustic waveshapers. In addition there is provided an overlap region between two adjacent waveshapers.

Abstract: A loudspeaker box (300) has a loudspeaker housing (1) and a sound source (3a) with a non-rotationally symmetrical radiation characteristic. The sound path of the sound source (3a) contains an acoustic element (4) which dilates or constricts the radiation of sound in at least one radiation plane. The loudspeaker box (300) comprises a mechanism which can be used to position the sound source (3a) and the acoustic element (4) in different rotational positions relative to one another.

Abstract: A ultra-slim includes bass, alto membranes and acoustical element, where a surrounding embossed pattern is configured on a location adjacent to the rim of the bass membrane to form a dangling edge, and a frame stopping portion formed by a step is disposed on the center thereof. Whereby, a groove formed by a step is disposed on the center of alto membrane, and the acoustical element is formed by stacking a plurality of ceramic material layers together, thereby mounting the acoustical element on the alto membrane, and then lodging the alto membrane in the inner edge of the frame stopping element of the bass membrane to construct a thinned speaker in which sound is guided out through the bass and alto membranes after audio signals are received, capable of the application thereof to thinned products such as iPad, iPhone, cellular phones or notebook computers.

Abstract: In a speaker, a space surrounded by a frame on one side of a diaphragm is separated by a damper into a first internal space and a second internal space. The first internal space and the second internal space are caused to face one part and another part of an opening provided in the frame. A duct protrudes from the frame, and the opening is an open end of the duct on the base end side thereof. The speaker is installed, for example, outside a vehicle cabin with the duct inserted into an opening in a vehicle cabin wall, and the first and second internal spaces are caused to communicate with a space in the vehicle cabin through the duct. Therefore, reproduced sound in the bass range having a high sound pressure can be discharged through the duct to the space in the vehicle cabin.

Abstract: The present invention comprises a loudspeaker system that includes a loudspeaker and a detachable mount. In one or more embodiments, the loudspeaker and mount include electrical connectors that are engaged when the loudspeaker is attached to the mount. In one or more embodiments, the loudspeaker and mount comprise mating mounting structures that support the loudspeaker on the mount when the mounting structure of the loudspeaker is engaged with the mounting structure of the mount. In one or more embodiments, multiple configurations of the mount are provided that allow the loudspeaker to be mounted with a variety of orientations with respect to the mounting surface. In one or more embodiments, the loudspeaker comprises a tweeter with a rotatable wave guide that allows the dispersion angle of the tweeter to be adjusted to accommodate the variety of orientations at which the loudspeaker may be mounted.

Abstract: A directional waveguide array apparatus can transmit and/or receive airborne or fluid-borne audio with the appropriate selection of transducers. The present invention advances directional waveguide arrays by allowing construction of a directional audio device with desired frequency bandwidths, array patterns, and gain by appropriate geometric configurations of the array of waveguide channel ports, as well as dimensioning and configuration of waveguide channel and chamber parameters. Embodiments of the present invention enable increased immunity to environmental noises, temperature, and humidity; low cost of construction; high reliability; simplicity of operation; very low power consumption; real-time steering of directivity (interference) pattern; wide range of audio powers that can be transmitted or received; and interchangeable transducer types.

Abstract: A loudspeaker apparatus has at least one sound generator wherein an at least partially sound-conducting channel is arranged in a sound radiation direction of the sound generator and is suitable for directing sound emerging from the sound generator along the course of the sound-conducting channel such that the sound emerges from the loudspeaker apparatus at a second end of the sound-conducting channel, which end is in the form of a sound outlet opening, at a radiation angle which defined by the sound outlet opening.

Abstract: A horn assembly for high frequency acoustic speakers. In an array of speakers, a spacing between adjacent speakers needs to be less than the wavelength of sound being emitted in order to combine effectively. For high frequency sound, a relatively small wavelength imposes a limitation on such a spacing. Such limitations are sometimes physically difficult to implement. A horn assembly increases the exit dimensions of the small speaker to larger desired dimensions by utilizing one or more plugs that divide a larger horn cavity into smaller horn cavities and creating similar pathlengths thereto. The similar pathlengths and the smaller horn cavities having desired dimensions allow the exiting sound to combine effectively. The overall dimensions of the exit portion of the horn assembly can be selected to match the dimensions of larger bass speakers, thus allowing improved arraying of the high frequency speakers with respect to other larger speakers.

Abstract: Systems, apparatus, devices, and methods for converting electrical signals into sound using an acoustic transducer. The inventive acoustic transducer utilizes the motion of an airfoil shaped element to generate a sound wave, with the airfoil element being driven in response to an electrical signal input to a suitable driving element. In some embodiments, the airfoil element or elements act to mechanically couple the motion of an armature attached to the driver to the surrounding air, producing sound waves in a more efficient manner than typical acoustic transducer devices. Embodiments of the invention may be used in the design of loudspeakers, earpieces, headphones, and other devices for which a high efficiency transducer is desired.

Abstract: An electrical to audible signal measurement apparatus comprises an absolute value converter, a voltage to frequency converter, a polarity detector, and a waveform changer. The absolute value converter is capable of converting a bipolar input signal into a unipolar signal. The voltage to frequency converter is connected to the absolute value converter and is capable of generating a frequency signal proportional to the unipolar signal. The polarity detector is capable of identifying a polarity of the bipolar input signal to form an identified polarity. The waveform changer is connected to the voltage to frequency converter and polarity detector and is capable of generating a number of different waveforms in an audio frequency range in response to receiving the frequency signal from the voltage to frequency converter and in response to the identified polarity.

Abstract: A resonance device for a speaker is provided. The device includes a speaker unit and a resonance unit. The speaker unit outputs a sound corresponding to a signal. The resonance unit is fixed to the speaker unit to provide a space for allowing a sound to resonate. The resonance unit is flexible, and the space for allowing a sound to resonate is variable.

Abstract: A flat panel loudspeaker with such an emission characteristic is obtained which, in the event of the flat panel loudspeaker being set up inversely, provides an improved listening result in that a loudspeaker is provided within the housing, and a sound conduction is configured such that sound from the loudspeaker is conducted outward via an acoustic aperture within the housing for undirected emission.

Abstract: A speaker box and a speaker device that can be manufactured at low cost and that provide a sound-absorbing effect. A speaker box of a speaker device includes a baffle, four intermediate plates, and a rear plate. The baffle plate has a speaker mount hole at the center. Each intermediate plate has a hole. The intermediate plates are stacked such that they are alternately reversed or rotated so that the holes in the adjacent intermediate plates communicate with each other while the holes are shifted from with each other. A hollow space with a sound-absorbing effect is formed by the holes in the speaker box.

Abstract: A method for making a thermoacoustic module is disclosed. An insulating substrate and a sound wave generator are provided. A conductive paste is screen printed on the insulating substrate to form a first patterned conductive paste layer. The sound wave generator is placed on the first patterned conductive paste layer and at least partially suspended above the insulating substrate by the patterned conductive paste layer.

Abstract: An omnidirectional speaker having a high frequency driver, which generates sound over a high frequency range and which has a first diameter, and a high frequency waveguide having a second diameter larger than the first diameter. A first midrange driver and a second midrange driver have a third diameter and a fourth diameter, respectively. Each midrange driver generates sound over a middle frequency range and the first midrange driver faces the second midrange driver. First and second midrange waveguides have a fifth diameter and a sixth diameter, respectively, and correspond to the first and second midrange drivers, respectively. The fifth diameter is larger than the third diameter and the sixth diameter is larger than the fourth diameter. Both of the midrange frequency waveguides are positioned between the first midrange driver and the second midrange driver so as to block a direct path from the first midrange driver to the second midrange driver.

Abstract: The present invention allows for the further enhancement of a low pitch range with a simple structure without increasing the size. The present invention is provided with: a pipe (102) open one end side and the other end side; a speaker unit (104) that is coaxial with the pipe (102), arranged at the one end side of the pipe (102), and driven on the basis of an audio signal; and an edge-cum-diaphragm (102B) that is coaxial with the pipe (102), installed at the other end side of the pipe (102), and vibrates in response to a sound wave that passes through the pipe (102). While the pipe (102) functions as a resonance tube by being excited to vibration with the sound wave that is radiated from the speaker unit (104) and passes through the pipe (102), the edge-cum-diaphragm (102B) functions as a passive radiator by vibrating in response to the sound wave that passes through the pipe (102).

Abstract: Methods and apparatus are provided for waveguide structures and speaker assemblies. In one embodiment, a waveguide may include an input aperture configured to receive a sound signal from a sound source, and a plurality of isolated sound paths having substantially equal path lengths. Each isolated sound path may be formed within a housing of the waveguide and formed with a curved path to reduce the depth of the waveguide. The waveguide may include a plurality of plugs, wherein each plug divides an output of one of the isolated sound paths into a plurality of output sound paths and defines a plurality of output apertures of the waveguide. Each output sound path is characterized by a reduced width relative to the output of the isolated sound path, the plurality of output apertures configured to output a combined sound signal based, at least in part, on the plurality of sound signals.

Abstract: A loudspeaker having a vented enclosure with at least one tuning port includes a fan inside the vented enclosure, which is positioned to produce airflow for cooling the magnetic assembly of the loudspeaker's transducer. Airflow within said vented enclosure is produced such that air within the enclosure is exchanged with outside air through the at least one tuning port. Typically, the vented enclosure will have two tuning ports wherein outside air drawn into the enclosure through one of the tuning ports is circulated out through the other tuning port. Preferably, the outside air drawn in through one tuning port is circulated directly around the transducer magnetic assembly for greatest heat dissipation.

Abstract: Provided is a technique for improving frequency characteristics by an acoustics-related method so that a sound is heard with natural frequency characteristics when a sound-isolating earphone is fitted in a human ear. A sound-isolating earphone is provided with two or more electroacoustic transducers, wherein independently generated sound waves are passed through isolated sound leading pipes and are mixed just before an entrance of an external auditory canal, and a sound wave of which is twice the difference between path lengths of the two sound leading pipes is attenuated. This serves to provide an easy-to-hear improved sound quality by suppressing the sound wave at around 6 kHz that is transmitted with characteristically high intensity in a sound-isolating earphone.

Abstract: According to one embodiment, an acoustic semiconductor device includes an element unit, and a first terminal. The element unit includes an acoustic resonance unit. The acoustic resonance unit includes a semiconductor crystal. An acoustic standing wave is excitable in the acoustic resonance unit and is configured to be synchronously coupled with electric charge density within at least one portion of the semiconductor crystal via deformation-potential coupling effect. The first terminal is electrically connected to the element unit. At least one selected from outputting and inputting an electrical signal is implementable via the first terminal. The electrical signal is coupled with the electric charge density. The outputting the electrical signal is from the acoustic resonance unit, and the inputting the electrical signal is into the acoustic resonance unit.

Abstract: The present technology provides a sophisticated level of control of the spatial pattern of an acoustic field which can overcome or substantially alleviate problems associated with transmitting an acoustic signal within the near-end acoustic environment. The spatial pattern is produced by utilizing an array of audio transducers which generate a plurality of acoustic waves forming an acoustic interference pattern, such that the resultant acoustic energy is constrained (e.g. limited to an acoustic energy level at or below a predetermined threshold level) in one or more regions of the spatial pattern. In doing so, listeners in these region(s) may not receive sufficient acoustic energy to hear the associated acoustic signal, while listeners in other regions can. Similarly, these techniques can suppress echo paths within those region(s).

Abstract: A loudspeaker assembly, including an acoustic waveguide; an acoustic driver mounted in the waveguide so that a first surface radiates sound waves into the waveguide so that the sound waves are radiated from the waveguide; and an acoustic volume acoustically coupled to the acoustic waveguide for increasing the amplitude of the sound waves radiated from the acoustic waveguide.

Abstract: An approach for enabling audio content to be directed to a select user from any location within a premises is described. A directional sound module determines a signal strength of a mobile device associated with a user relative to a wireless access point located within a premises and correlates the signal strength to a reference location within the premises based on predetermined wireless fingerprint information. The directional sound module then determines a direction to transmit an ultrasound signal for conveying audible sound to the user.

Abstract: An audio driver including a diaphragm with a first side and a second side. The diaphragm is coupled to a transducer element on the second side and is arranged to radiate sound. The transducer element converts an electrical input signal into movement of the diaphragm. The diaphragm is arranged such that a part of the diaphragm at least partly forms a cavity at the second side of an air conduit is coupled to the cavity. The air conduit has a first opening into the cavity and a second opening outside of the cavity. The air conduit and cavity form a resonator which has a resonance frequency that is less than half a free air acoustic resonance frequency of the audio driver.

Abstract: Disclosed are portable devices having function for providing information and contents related to various kinds of acoustic sources, apparatuses for providing acoustic source information, and methods for providing acoustic source information. The portable device includes characteristic code extractor and controller. The characteristic code extractor receives acoustic source to divide the acoustic source into audio signal with audio frequency band and signal with supersonic frequency band, and extracts characteristic code of the audio signal with the audio frequency band from the signal with the supersonic frequency band. The controller transmits the characteristic code to acoustic information server, and outputs the acoustic source information corresponding to the characteristic code that is provided from the acoustic information server.

Abstract: A loudspeaker system according to the present invention includes a cabinet, a loudspeaker unit attached to an opening formed in the cabinet, a gas adsorber provided in the cabinet and operable to physically adsorb gas in the cabinet to equivalently increase a volume of an inside of the cabinet, and a dehumidifier attached to an opening formed in the cabinet and operable to discharge damp air in the cabinet to the outside when a DC voltage is applied thereto.

Abstract: A flat panel piezoelectric loudspeaker includes a piezoelectric element, a first electrode and a second electrode. The piezoelectric element includes a first surface and a second surface opposite to the first surface. The first electrode is electrically connected to the piezoelectric element and disposed on the first surface. The second electrode is electrically connected to the piezoelectric element and disposed on the second surface. At least one of the first electrode and the second electrode includes a carbon nanotube structure. The carbon nanotube structure includes a plurality of carbon nanotubes approximately aligned along a same direction.

Abstract: A directional waveguide array apparatus can transmit and/or receive airborne or fluid-borne audio with the appropriate selection of transducers. The present invention advances directional waveguide arrays by allowing construction of a directional audio device with desired frequency bandwidths, array patterns, and gain by appropriate geometric configurations of the array of waveguide channel ports, as well as dimensioning and configuration of waveguide channel and chamber parameters. Embodiments of the present invention enable increased immunity to environmental noises, temperature, and humidity; low cost of construction; high reliability; simplicity of operation; very low power consumption; real-time steering of directivity (interference) pattern; wide range of audio powers that can be transmitted or received; and interchangeable transducer types.

Abstract: A receiver or loudspeaker having a plurality of sound generators each having a housing and a sound output. An oblong channel is formed by a channel-forming element and parts of the housings. The sound outputs are positioned on one side of a middle of the channel and a outlet of the channel is positioned on the other side of the middle of the channel so that the channel has a length adapted to acoustically alter the sound. The use of the housings for forming the channels provides a more compact structure.

Abstract: An apparatus includes a housing. A waveguide is located within the housing. The waveguide includes a first subsection that bends around a first axis and has a first cross-sectional area with an aspect ratio that is substantially different from unity. A second subsection bends around a second axis that is non-parallel to the first axis and includes a second cross-sectional area with an aspect ratio that is substantially different from unity. A third subsection acoustically couples the first subsection to the second subsection. The third subsection includes a third cross-sectional area with an aspect ratio that varies between the first aspect ratio and the second aspect ratio.

Abstract: There is provided a dock without a power source for a portable digital device with at least one integrated speaker driver. The dock may include a platform for placement of the portable digital device; a protrusion located at the platform for connection of the portable digital device with the dock with the protrusion including a slot for egress of air from at least one hole in a casing of the portable digital device to the dock; and at least one primary chamber to receive air from the portable digital device with the at least one primary chamber having a vented port for the egress of air. Advantageously, sound from the at least one integrated speaker driver is amplified when the portable digital device is connected to the dock. The connection of the portable digital device with the dock may be securable.

Abstract: A docking station for sound amplification and sound quality enhancement is provided. The docking station includes a support structure for holding a mobile terminal having an internal speaker to sustain the posture of the mobile terminal, and a body for supporting the support structure, and for physically contacting the speaker to increase the volume of sound output from the speaker. The body includes a collecting hole for contacting the speaker to collect sound waves, and a guide hole that extends from the collecting hole through the body to the outside along an extension direction, is divided into two branches within the body to guide the collected sound waves along different paths, and has a horn shape whose cross section increases along the extension direction. Hence, the docking station can increase the volume of audible sound and sound quality without separate supply of power.

Abstract: A mobile communication device is provided. The mobile communication device includes a terminal body, and a speaker module located in the terminal body. The speaker module includes an enclosure located in the terminal body, the enclosure defining a chamber therein, and a speaker having a front surface and a rear surface, the speaker being located in the enclosure such that the front surface of the speaker is exposed from the enclosure and the rear surface thereof is positioned within the chamber, to allow a sound generated from the rear surface to resonate within the chamber. A mutual interference between the sound generated from the front side of the sound emission part and the sound emitted from the rear side thereof can be reduced to thereby improve the performance of the middle and low sound.