Abstract: An apparatus comprises an agglomeration of adsorbing members, each of the adsorbing members comprising a porous outer layer configured to enclose an amount of adsorbent material, the agglomeration being configured such that every cross-section through the agglomeration comprises at least one gap between adjacent adsorbing members.

Abstract: A loudspeaker enclosure has a first aperture in which a driver can be mounted, the driver having a first resonant frequency. A second aperture defines a port extending between the interior and the exterior of the enclosure. The port is tuned to a second resonant frequency. A sound absorbing element comprises at least one exponentially tapered horn having a mouth in communication with the interior of the enclosure. The horn has a cut-off frequency equal to or greater than the resonant frequency of the port, and preferably two to four times greater. The horn can be defined by tapering external walls of the enclosure, or by structures located within the enclosure which define a plurality of individual horns. The described enclosure combines the benefits of ported enclosures with those of enclosures employing tapered sound absorbing elements.

Abstract: The present invention provides a recoilless speaker system capable of reducing adversely affecting vibration and generating an accurate and strong sound, and contributing to the realization of lighter weight, miniaturization and lower cost related to manufacturing, and also capable of being installed in a suspended state and generating sound even under zero gravity as long as air exists. The present invention includes a symmetrical and tubular resonance wall and a pair of or two or more pairs of vibration units symmetrically arranged on both left and right sides of the resonance wall, where the vibration units that form a pair are configured to vibrate synchronously with each other, the resonance wall is made from a flexible material so as to resonate to the vibration, a sound absorbing member is arranged in a tubular form along the inner wall of the resonance wall, and vibration suppressing materials are held at the sound absorbing member and/or the vibration unit.

Abstract: In an anti-vibration device 10 including: an outer cylinder 11, an attachment member 12, a rubber elastic portion 13 which elastically connects the outer cylinder 11 to the attachment member 12, a primary liquid chamber 16 which encloses a liquid therein by using the rubber elastic portion 13 as a part of a partition wall, a secondary liquid chamber 17 which encloses a liquid therein by using a diaphragm 14 as a part of a partition wall, an orifice 19 which allows the primary liquid chamber 16 and the secondary liquid chamber 17 to communicate with each other, a division member 15 which is provided between the primary liquid chamber 16 and the secondary liquid chamber 17, and a movable plate 18 which displaces in accordance with a pressure difference between the primary liquid chamber 16 and the secondary liquid chamber 17, the division member 15 including a first division plate 21 forming a part of the partition wall of the primary liquid chamber 16 and a second division plate 22 forming a part of the partit

Abstract: An acoustic waveguide with at least two portions coupled by vibration damping structure. The vibration damping structure may be a conformable material such as closed cell foam. The vibration damping structure may further include structure for inhibiting motion in a direction transverse to the interface between the vibration damping structure and a portion of the waveguide.

Abstract: A compound loudspeaker comprises an acoustically radiating first diaphragm and an acoustically radiating second diaphragm. The first and second diaphragms are substantially coaxial and at least part of the second diaphragm is situated radially outwards of the first diaphragm. There is a gap situated between the first and second diaphragms, and a seal is provided in the gap, thereby preventing or hindering the passage of air through the gap. By providing the seal, the invention solves the problem of audible turbulent airflow through the gap.

Abstract: A speaker enclosure having a substantially seamless rigid outer skin, a middle sound absorbing layer, and a substantially seamless inner skin results in a lightweight speaker having sound absorbing characteristics. The speaker enclosure is comprised of two basic parts, a box section and a baffle section where each of these sections include a rigid outer skin, the middle sound absorbing layer and a seamless inner skin and are made according to the same method. The outer skin is formed from a layer of sheet molding compound, the middle sound absorbing layer includes pieces of honeycomb material, and the inner skin is formed from a layer of sheet molding compound. The layers of material are placed into a mold and then cured through vacuum bagging and heating thereby producing a strong, lightweight speaker enclosure made of materials which attenuate the transmission and retransmission of errant sound waves in the enclosure thereby reducing distortion of the sound signal produced by the speaker.

Abstract: An acoustic waveguide with at least two portions coupled by vibration damping structure. The vibration damping structure may be a conformable material such as closed cell foam. The vibration damping structure may further include structure for inhibiting motion in a direction transverse to the interface between the vibration damping structure and a portion of the waveguide.

Abstract: An acoustic waveguide with at least two portions coupled by vibration damping structure. The vibration damping structure may be a conformable material such as closed cell foam. The vibration damping structure may further include structure for inhibiting motion in a direction transverse to the interface between the vibration damping structure and a portion of the waveguide.

Abstract: In an anti-vibration device 10 including: an outer cylinder 11, an attachment member 12, a rubber elastic portion 13 which elastically connects the outer cylinder 11 to the attachment member 12, a primary liquid chamber 16 which encloses a liquid therein by using the rubber elastic portion 13 as a part of a partition wall, a secondary liquid chamber 17 which encloses a liquid therein by using a diaphragm 14 as a part of a partition wall, an orifice 19 which allows the primary liquid chamber 16 and the secondary liquid chamber 17 to communicate with each other, a division member 15 which is provided between the primary liquid chamber 16 and the secondary liquid chamber 17, and a movable plate 18 which displaces in accordance with a pressure difference between the primary liquid chamber 16 and the secondary liquid chamber 17, the division member 15 including a first division plate 21 forming a part of the partition wall of the primary liquid chamber 16 and a second division plate 22 forming a part of the partit

Abstract: The present invention relates to a soundproof cover for automobiles, the soundproof cover including: a cover body formed of a metal or a resin; and a sound-absorbing material disposed opposite to a sound source, in which the sound-absorbing material has a soft sound-insulating layer on a surface side thereof facing the cover body, the sound-absorbing material is disposed apart from the cover body, and the sound-absorbing material has a peripheral edge that contacts with an inner wall of an edge of the cover body.

Abstract: A vehicle door structure, comprising: a loudspeaker mounting hole provide in a door inner panel of a vehicle; a first service hole provided in the door inner panel and located in the vicinity of the loudspeaker mounting hole; a second service hole provided in the door inner panel and located at a position more distant than the first service hole from the loudspeaker mounting hole; a loudspeaker mounted in the loudspeaker mounting hole; a plate-shaped member screwed to the door inner panel for closing the first service hole; and a sound absorbing member provided to close the second service hole.

Abstract: An acoustic material is intended to be mounted behind a loudspeaker 8 to decrease the resonant frequency and/or to reduce the back volume. The acoustic material includes a woven or non-woven fabric which supports highly porous particles or fibers such as particles of carbon black. The woven or non-woven is thin and light to avoid damping sound, whilst still being capable of retaining the porous material. The use of a flexible acoustic material allows the material to be more easily included with loudspeakers in portable mobile devices.

Abstract: An apparatus comprises an agglomeration of adsorbing members, each of the adsorbing members comprising a porous outer layer configured to enclose an amount of adsorbent material, the agglomeration being configured such that every cross-section through the agglomeration comprises at least one gap between adjacent adsorbing members.

Abstract: A speaker system that includes a speaker unit, a cabinet, a plurality of protruding materials, and a gas adsorbing material. The cabinet forms a chamber at a backside of the speaker unit. The plurality of protruding materials are formed inside the chamber and connected to the cabinet. The gas adsorbing material is supported, in a space, by the plurality of protruding materials. Accordingly, it is possible to easily increase a contact area between the gas adsorbing material and the space theresurrounding.

Abstract: A sound absorbing structure includes a housing having a front face, and a side face which is provided perpendicularly around at least a part of an edge portion of the front face; a gas adsorption material for physically adsorbing gas in an interior space delimited by the front face and the side face of the housing, which gas adsorption material is placed in the interior space; sealing element for sealing the gas adsorption material from outside thereof; and an acoustic connection section for functioning as an acoustic mass so as to acoustically connect an exterior space and the interior space of the housing, which acoustic connection section is provided in at least one of the front face and the side face.

Abstract: In a noise suppression structure of the present invention, a sound absorption sheet is pinched between a flange of a speaker grille and an interior trim. An opening of a space formed by the flange of the speaker grille and a sound guiding tube is covered with the sound absorption sheet.

Abstract: A speaker enclosure having a substantially seamless rigid outer skin, a middle sound absorbing layer, and a substantially seamless inner skin results in a lightweight speaker having sound absorbing characteristics. The speaker enclosure is comprised of two basic parts, a box section and a baffle section where each of these sections include a rigid outer skin, the middle sound absorbing layer and a seamless inner skin and are made according to the same method. The outer skin is formed from a layer of sheet molding compound, the middle sound absorbing layer includes pieces of honeycomb material, and the inner skin is formed from a layer of sheet molding compound. The layers of material are placed into a mold and then cured through vacuum bagging and heating thereby producing a strong, lightweight speaker enclosure made of materials which attenuate the transmission and retransmission of errant sound waves in the enclosure thereby reducing distortion of the sound signal produced by the speaker.

Abstract: A device for noise transmission of an intake system of an internal combustion engine to the interior of a motor vehicle has a transmission line having an inlet at a first end and an exit provided with a mouth at a second end. A diaphragm is arranged at the second end to close off the mouth and to enable noise transmission. The inlet of the transmission line communicates with the intake system of the internal combustion engine. A protective device is arranged at the second end to protect the diaphragm.

Abstract: A sound enhancement module includes a set of walls that define an enclosed chamber, an aperture in one of the walls to provide a path for audio waves to travel between the enclosed chamber and an external space and an alternative density transmission medium positioned in the enclosed chamber.

Abstract: A speaker attenuation system includes a foam attenuating member attached to a mounting bracket. The mounting bracket is configured for attachment to a baffle board of a speaker cabinet and the foam attenuating member is configured to be positioned in a central beam region of a speaker of the speaker cabinet when the mounting bracket is attached to the baffle board.

Abstract: A sound absorbing structure is constituted of a housing having a hollow portion and an opening and a vibration member composed of a board or diaphragm. The vibration member is a square-shaped material having elasticity composed of a synthetic resin and is bonded to the opening of the housing, thus forming an air layer closed inside the sound absorbing structure by the housing and the vibration member. In the sound absorbing structure, when the lateral/longitudinal dimensions of the air layer and characteristics of the vibration member (e.g. a Young's modulus, thickness, and Poisson's ratio) are set such that the fundamental frequency of a vibration occurring in a bending system falls within 5% and 65% of the resonance frequency of a spring-mass system, a vibration mode having a large amplitude occurs in a frequency band lower than the resonance frequency of the spring-mass system, this improving the sound absorption coefficient.

Abstract: Embodiments include an acoustic source for use in a hemi-anechoic chamber comprising a source assembly and a waveguide assembly for producing sound outside of a measurement hemisphere and channeling the sound into the measurement hemisphere. A waveguide end from which sound emanates is positioned close to the reflecting plane of the chamber and can approximate a point source.

Abstract: A speaker system includes a speaker unit, a cabinet, a plurality of protruding materials, and a gas adsorbing material. The cabinet forms a chamber at a backside of the speaker unit. The plurality of protruding materials are formed inside the chamber and connected to the cabinet. The gas adsorbing material is supported, in a space, by the plurality of protruding materials. Accordingly, it is possible to easily increase a contact area between the gas adsorbing material and the space the resurrounding.

Abstract: A method of mounting a speaker enclosure for a ceiling or wall mounted speaker which includes the selection of a flexible polymer speaker housing forming a hollow chamber having a speaker opening therein and being collapsible to a smaller size. A hole is cut into a building, ceiling or interior wall and a selected speaker housing is collapsed to a size to fit through the speaker opening in one side of a ceiling or wall. The collapsed flexible polymer speaker housing is then expanded on the other side of the ceiling or wall and attached to the ceiling or wall with an adhesive or the like adjacent the opening and a speaker attached to the ceiling or wall opening.

Abstract: A supersonic boom simulator constructed from a directed coherent sound pulse source, a waveguide and a bass trap at the opposite end of the waveguide from the directed coherent sound pulse source.

Abstract: A noise isolation device includes a plurality of panels comprising a sound absorbent material for assembling into an enclosure for a pump mechanism and a plurality of fasteners built into the panels for assembling the panels to form an enclosure for a pump mechanism and for disassembling the panels to remove the enclosure from the pump mechanism.

Abstract: A speaker having a transparent sound panel and an exciter connected to the transparent sound panel for converting electrical energy received by the exciter, into vibrations that are transmitted to the transparent sound panel, resulting in the transparent sound panel transmitting sound. The speaker also contains a stiff panel located between the exciter and the transparent sound panel, where the stiff panel minimizes dampening qualities associated with material utilized to fabricate the transparent sound panel and minimizes bending of the portion of the transparent sound panel that is in contact with the stiff panel. In addition, a dampening pad is located within the exciter for absorbing a portion of excessive mid-high frequency vibrations emanating from the exciter prior to transmission to the transparent sound panel.

Abstract: A sound absorbing structure according to the present invention comprises: a housing having a front face, and a side face which is provided perpendicularly around at least a part of an edge portion of the front face; a gas adsorption material for physically adsorbing gas in an interior space delimited by the front face and the side face of the housing, which gas adsorption material is placed in the interior space; sealing means for sealing the gas adsorption material from outside thereof; and an acoustic connection section for functioning as an acoustic mass so as to acoustically connect an exterior space and the interior space of the housing, which acoustic connection section is provided in at least one of the front face and the side face. The sound absorbing structure according to the present invention realizes both sound absorption in a low-pitched range and a reduction in the size of the structure.

Abstract: A process and kit is provided for retro-installing a speaker enclosure for a wall mounted speaker. The process includes mounting a selected speaker surround member in a building wall between the front and back wall surfaces and between the wall studs and around the opening for a wall mounted speaker and adhesively mounting a selected sheet of vibration dampening material to the back wall surface behind the opening for the wall mounted speaker and attaching a flexible sound absorbent material to the vibration dampening material so that a wall mounted speaker enclosure is installed in an existing building wall.

Abstract: A speaker enclosure having a substantially seamless rigid outer skin, a middle sound absorbing layer, and a substantially seamless inner skin results in a lightweight speaker having sound absorbing characteristics. The speaker enclosure is comprised of two basic parts, a box section and a baffle section where each of these sections include a rigid outer skin, the middle sound absorbing layer and a seamless inner skin and are made according to the same method. The outer skin is formed from a layer of sheet molding compound, the middle sound absorbing layer includes pieces of honeycomb material, and the inner skin is formed from a layer of sheet molding compound. The layers of material are placed into a mold and then cured through vacuum bagging and heating thereby producing a strong, lightweight speaker enclosure made of materials which attenuate the transmission and retransmission of errant sound waves in the enclosure thereby reducing distortion of the sound signal produced by the speaker.

Abstract: The present invention relates to a novel acoustical chamber for enclosed loudspeakers which help direct and control sound waves within the enclosure thereby enhancing sound output. The present invention utilizes a method of progressive damping which utilizes multiple layers of damping material or layers of material with variable density or damping characteristics within an enclosed chamber. The damping material is arranged such that the density of the material in the chamber decreases as the distance from the driver increases. The damping materials may also be configured such that the density of the material in the chamber increases as the transverse distance from the center of the chamber increases, that is, the density of the material along the outer surfaces of the chamber is denser than material which is transversely inward from the outer surfaces.

Abstract: A speaker device for improving mid/high-range frequencies includes a magnetic base, a frame annularly mounted to the magnetic base, a cone mounted to an inner side of the frame, a voice coil mounted to the cone and suspended in a gap of the magnetic base, and a deadening phase plug mounted on a central portion of the magnetic base. The magnetic base includes a T-iron, a magnet, and a pole plate. The deadening phase plug is made of a sound-absorbing material for absorbing and eliminating sound waves generated by the voice coil and the cone.

Abstract: A loudspeaker cabinet with a laminated internal brace which has a first rigid layer coupled to a first exterior panel of the cabinet, a second rigid layer coupled to an a second exterior panel of the cabinet, and a damping layer affixed between the rigid layers where they overlap. Vibration, flexure, and expansion/contraction of the cabinet are damped by shearing forces applied to the damping layer as the rigid layers move in opposite, parallel directions.

Abstract: An acoustic impedance matching enclosure is provided having a driver loaded into a chamber buffering the throat/mouth of a closed loop transmission line. Transmission line consists of a termination member, outer and inner enclosure walls, high-density lining and throat/mouth area. Transmission line eliminates internal random standing waves while providing variable-frequency standing waves that through superposition of the waves compensates for mass-acceleration loss of the high-end of the driver output while damping the resonance of the driver. Alternative application of the acoustic impedance matching enclosure is that of compression loading the driver directly into the closed loop transmission line and using an acoustic low pass filter to translate the output into low frequencies only through a port.

Abstract: A loudspeaker system includes a loudspeaker drive unit (1) and a rear sound absorption system (20) having a multiplicity of tubes connected to the rear of the loudspeaker drive unit. In one example, the rear sound absorption system (20) comprises a collector tube (22) for sound waves emerging from a passage in the magnet assembly of the loudspeaker drive unit, an annular diffuser (24) for sound waves coming from the back of the diaphragm (4), and a disk-shaped diffuser (26) for second waves collected by the collector tube (22). The disk-shaped diffuser (26) is part of a basket-like assembly (28) mounted on the rear of the magnet assembly (6). The annular diffuser (24) is mounted against the wall (2) of the enclosure in which the loudspeaker drive unit (1) is mounted. The annular diffuser (24) includes a base portion (24A) with integral upstanding vanes (24B) arranged in a spiral configuration.

Abstract: A small-sized speaker system having a very excellent bass-range reproduction capability includes a sound radiation component for guiding acoustic waves radiated from the speaker units to a free space by causing a larger degree of air compression and expansion than in the case where acoustic waves are directly radiated to the free space with the speaker units mounted in corresponding enclosures of the same shape as the speaker units. The speaker system has 20% or more lower f0 than in the case where acoustic waves are directly radiated to the free space with the speaker units mounted in corresponding enclosures of the same shape as the speaker units.

Abstract: A sound transmitter includes at least a vibrating membrane mounted on the wall of an enclosure so that one surface of the speaker membrane radiates in the enclosure, the enclosure being provided with a vent forming a conduit between an outlet inside the enclosure and an outlet outside the enclosure. The vent comprises aerodynamic turbulence attenuating elements at least at one of the outlets, the turbulence resulting from an air stream caused by the large amplitude displacements of the membrane. The invention also concerns a sound transmitter wherein air moves in a conduit (33) extending from the membrane to an outlet (35) of the conduit (33) on the outside. The invention further concerns a speaker whereof the members have an aerodynamic shape.

Abstract: A speaker enclosure having a substantially seamless rigid outer skin, a middle sound absorbing layer, and a substantially seamless inner skin results in a lightweight speaker having sound absorbing characteristics. The speaker enclosure is comprised of two basic parts, a box section and a baffle section where each of these sections include a rigid outer skin, the middle sound absorbing layer and a seamless inner skin and are made according to the same method. The outer skin is formed from a layer of sheet molding compound, the middle sound absorbing layer includes pieces of honeycomb material, and the inner skin is formed from a layer of sheet molding compound. The layers of material are placed into a mold and then cured through vacuum bagging and heating thereby producing a strong, lightweight speaker enclosure made of materials which attenuate the transmission and retransmission of errant sound waves in the enclosure thereby reducing distortion of the sound signal produced by the speaker.

Abstract: The system consists of 2 large speakers (1A & 1B), and 2 small full range speakers (2A & 2B) having about half the active cone area as the large speakers, mounted in a dual chamber enclosure (3) with the large speaker (1A) mounted on an internal baffle (4) forming a partition for a large bass reflex chamber (3A), with the large speaker (1B) mounted in common direction thereto immediately in front thereof together with the 2 smaller speakers (2A & 2B) mounted adjacent thereto on a front baffle (7) forming a small tympanic chamber (3B) by and with the large speakers (1A & 1B) and small speaker (2B) electrically connected to operate in common acoustic phase to each other with the other small speaker (2A) connected to operate in opposing phase thereto.

Abstract: An acoustic enclosure such as a loudspeaker (10) uses within the cabinet adsorbent material, and/or containment means (22) for the adsorbent material, which is at least partially hydrophobic. Preferably, the material is activated carbon treated to provide it with hydrophobic properties. Preferably, the adsorbent material is treated with a silicon-containing compound. This improves the acoustic compliance of the acoustic enclosure.

Abstract: A loudspeaker system comprises a loudspeaker drive unit (1) and a rear sound absorption system (20) comprising a multiplicity of tubes connected to the rear of the loudspeaker drive unit. In one example, the rear sound absorption system (20) comprises a collector tube (22) for sound waves emerging from a passage in the magnet assembly of the loudspeaker drive unit, an annular diffuser (24) for sound waves coming from the back of the diaphragm (4), and a disk-shaped diffuser (26) for sound waves collected by the collector tube (22). The disk-shaped diffuser (26) is part of a basket-like assembly (28) mounted on the rear of the magnet assembly (6). The annular diffuser (24) is mounted against the wall (2) of the enclosure in which the loudspeaker drive unit (1) is mounted. The annular diffuser (24) comprises a base portion (24A) with integral upstanding vanes (24B) arranged in a spiral configuration.

Abstract: The invention concerns a sound transmitter comprising at least a vibrating membrane mounted on the wall of an enclosure so that one surface of the speaker membrane radiates in the enclosure, the enclosure being provided with a vent forming a conduit between an outlet inside the enclosure and an outlet outside the enclosure. The invention is characterised in that the vent comprises aerodynamic turbulence attenuating means at least at one of the outlets, said turbulence resulting from an air stream caused by the large amplitude displacements of the membrane. The invention also concerns a sound transmitter wherein air moves in a conduit (33) extending from the membrane to an outlet (35) of the conduit (33) on the outside. The invention further concerns a speaker whereof the members have an aerodynamic shape.

Abstract: The invention pertains to a device for reducing the noise level of, and for cooling, a Component (1) with moving parts, such as a hard disk in a PC system. The device comprises a Container (2) in which Component (1) is arrayed and in which Ventilation Openings (4) are provided on opposing sides, through which an air stream can flow for cooling the component. In accordance with the invention, Component (1) is completely surrounded by Sound-muting Material (3) in Container (2) and Channels (5) are configured in Sound-muting Material (3) for adducing and exhausting the cooling air.

Abstract: Acoustic diffuser comprising a containing element able to contain at least a loudspeaker, wherein the containing element is formed by a monocoque made with granules of solid mineral held together by a cohesion material.

Abstract: A casing for an acoustic equipment formed mainly of a filler and a thermosetting or thermoplastic resin. The filler is comprised of a cellulose-based powdered material, such as wooden powders obtained on crushing a wooden material and an powdered material smaller in size and harder than the cellulose-based powdered material. The powdered material is secured or deposited under a pre-set pressure on the surface of the cellulose-based powdered material.

Abstract: A device (8) which includes an electroacoustic transducer (7) for the acoustic reproduction of sound signals to an ear (14) of a user (2) who assumes a user position at the device. The transducer is optimized for the acoustic reproduction of speech-signal sound waves and is equipped with arrangement means (25) for realizing a distinct directivity for the speech-signal sound waves emitted by the transducer. As a result of its directivity, the transducer directs the speech-signal sound waves which it emits preferentially to the ear of a user who is in the user posture.

Abstract: A passive radiator includes a chassis (11) and a radiator body which is connected to the chassis and which is movable with respect to the chassis along a translation axis (T*). The radiator is capable of displacing comparatively large air volumes. The radiator body includes a central mass element (13a) and at least one mass element (13b) which is arranged concentrically with respect to the central mass element. The radiator further comprises connection units for movably interconnecting each pair of adjacent mass elements and for movably connecting one of the mass elements to an element (11a) of the chassis. Each of the connection units includes two resilient annular connecting rings (5a1, 5a2; 5b1, 5b2), which have two adjacent elements which are parts of said elements secured to them. The connecting rings of at least one of the connection units bound a closed chamber (17a) containing a gaseous medium in order to counteract undesired noises.

Abstract: The present invention relates to loudspeaker cabinets composed of a moldable wood material and a method for making the same. In particular, the present invention relates to loudspeaker cabinets composed of a compression molded cellulose (CMC) material resulting in a cabinet for loudspeakers with improved acoustic and physical properties. In accordance with the present invention, a compression molded cellulose material, and a process for the mixing, extrusion, and compression molding of the compression molded cellulose material has been developed. Cabinet designs with rounded forms are made possible using the compression molded cellulose material and process. The characteristics of the compression molded cellulose material in combination with the unique shape of each cabinet is designed to enhance the fidelity of the sound produced by the loudspeaker mounted in the cabinet.

Abstract: A speaker system suppresses standing waves generated in the system and reproduces clear and dynamic bass sound. The system includes a cabinet formed of acoustic insulation walls, and at least one partition wall situated inside the cabinet to form a space by surrounding the space. The partition wall suppresses the standing waves generated inside the cabinet and is formed of a material having high internal loss. The space has a total capacity more than one tenth of a capacity of the cabinet, wherein a closed end of the partition wall is located between one-half and four-fifths of a distance from one end to the other end, and an opening area of the same partition wall is located at a side opposite to the closed end in a longitudinal direction of the cabinet. The opening area is located between four-fifths and five fifths of a distance from one end to the other end. The material has a density per volume greater than 0.1 g/cm3, a density per area from 0.01 g/cm2 to 0.