Abstract: Earmuffs with a joint are provided to create a biased pressure distribution about a perimeter of the cup. The earmuffs may include a pivot joint. The pressure distribution creates a wedging pressure (e.g., on a top edge) on the cups that hold the earmuffs on the user's head, for example, when the user rotates the headband behind the head. The bias pressure is also used to adjust the seal formed between the pad and the user's head. Adjustments to the moment created by separating the joints from the cup's apex enable a user to selectively adjust the seal according to the user's preference. A cam is added to the headband to change the hoop stress distributed at the joints and further adjust the compressive forces generated to hold the earmuffs against the user's head.

Abstract: The disclosure provide a device for protecting the hearing of animals. The device is a sound protection cap constructed of formable material, e.g., a soft acoustical material, and adjustable straps to comfortably fit over the ears and on the head of an animal, such as a dog. The sound protection cap can come in different sizes to insure a good fit regardless the ear type or head shape of the animal. The multiple adjustments and formable material allows the sound protection cap to conform around the ears/head of the animal and stay in place. The sound protection cap can be positioned on an animal to provide hearing protection throughout exposure to loud sounds. In one example, the sound protection cap includes: (1) an adjustable attachment system (AAS) and (2) an external ear cover (EEC) coupled to the AAS, wherein the EEC includes a sound reduction layer of a moldable material.

Abstract: A method and system for a headset with internal gimbal, where the headset comprises a headband, a headband, and ear cups coupled to the headband, wherein each ear cup may be coupled to the headband utilizing an internal gimbal. The internal gimbal may comprise a tip that is wider than its base. The tip may be rounded. The headband may comprise headband endcaps at each end of the headband. A headband slide may be coupled to each headband endcap. The headband ear cups may be coupled to the headband via the headband slides. Each headband slide may be coupled to a headband endcap via a headband pivot. The headband pivot may provide rotational motion of the ear cups with respect to the headband. The force on ears of a user of the headset may be spread evenly by the internal gimbals.

Abstract: The present disclosure relates to a system 10 comprising an ear cushion 20 for a headset 100, a fluid supply 30 and a fluid guide device 40 connected to the ear cushion 20. The present disclosure further relates to an ear cushion 20 for a headset 100, a fluid guide device 40 for a headset 100. Moreover, the present disclosure relates to a headset 100 as well as to a headgear 200 comprising such a system 10.

Abstract: A personal acoustic system and flexible mount for the same are disclosed. The flexible mount is comprised of an elastomeric material. The personal acoustic system further includes a band comprising a first mount and an earpiece comprising a second mount. An acoustic element is housed within the earpiece. The elastomeric mount is positioned intermediate the first mount and the second mount to flexibly connect the band to the earpiece.

Abstract: A hearing protection assembly for wearing a face mask with ear muffs includes a pair of ear muffs that can be worn over a user's ears thereby facilitating the ear muffs to protect the user from being exposed to excessive sound levels. Each of the ear muffs has a groove integrated therein to accommodate a respective one of a pair of ear loops of a face mask when the ear muffs and the face mask are both worn. A plurality of straps is each coupled to a respective one of the ear muffs. Each of the straps is extendable across the groove in the respective ear muff to retain the respective ear loop of the face mask in the groove in the respective ear muff.

Abstract: An electronic device such as a pair of headphones may be configured to be worn on a head of a user. The headphones may have a headband and earcups that are coupled to the headband. The headband may have a frame and a headband frame cover that is removably attached to the frame. The cover may have protrusions, may be inflated using a pump, may include a battery and other components, and may include sensors. An earcup movement synchronization mechanism may be used to synchronize movement of a left earcup with a right earcup. A torsion spring with a stop mechanisms or other bend limiter may be configured to prevent overbending of the headband.

Abstract: A headband or head cover including an elastic glitter or plain ribbon, a top portion of which forms the outside of the headband, where the elastic glitter or plain ribbon has a substantially 360-degree glitter pattern. The headband further includes a stretch velvet ribbon, a bottom portion of which forms the inside of the headband. The elastic glitter or plain ribbon is attached to the stretch velvet ribbon using a stretch and stitch method. The bottom of the stretch velvet ribbon includes a velvet-like material that forms a gripping portion. The outside of the headband includes a 360-degree view with no break. The inside of the headband includes 360-degree gripping portion with no break.

Abstract: A method and system for a headset with internal gimbal, where the headset comprises a headband, a headband, and ear cups coupled to the headband, wherein each ear cup may be coupled to the headband utilizing an internal gimbal. The internal gimbal may comprise a tip that is wider than its base. The tip may be rounded. The headband may comprise headband endcaps at each end of the headband. A headband slide may be coupled to each headband endcap. The headband ear cups may be coupled to the headband via the headband slides. Each headband slide may be coupled to a headband endcap via a headband pivot. The headband pivot may provide rotational motion of the ear cups with respect to the headband. The force on ears of a user of the headset may be spread evenly by the internal gimbals.

Abstract: Implementations of a ballistic helmet having an integrated electronic circuit are provided. An example ballistic helmet includes: a first armor plate attached by a hinge to a first side of the ballistic helmet, the first amor plate is configured and positioned to provide ballistic protection; a second armor plate attached by a hinge to a second side of the ballistic helmet, the second armor plate is configured and positioned to provide ballistic protection; and an integrated electronic circuit configured to operate and power electronic devices conductively coupled thereto.

Abstract: Improved monaural headsets are provided. In some embodiments, a monaural headset includes: a first earphone with a speaker to provide output audio to a user; a second earphone without a speaker to provide output audio to the user; and a headband, connected to the first earphone and the second earphone; wherein the second earphone includes at least one vent opening, which vent opening during use provides an acoustic path between an environment of the user, wearing the headset, and the user's ear.

Abstract: A headset includes an earpiece coupled to a headband with a membrane coupling. The earpiece includes an outer housing and an audio driver positioned within and coupled to the outer housing. The membrane coupling includes a membrane insert composed of a resilient material. The membrane insert is coupled to the outer housing. A connection pin may extend through a central opening of the membrane insert and into an end of the headband in order to directly couple the end of the headband to the membrane insert in order to couple the outer housing to the end of the headband. The coupling of the end of the headband to the outer housing with the membrane insert in between defines the membrane coupling. The membrane coupling is designed to allow relative movement in six degrees of freedom comprising three orthogonal degrees of translation freedom and three orthogonal degrees of rotational freedom.

Abstract: Presented herein are systems, methods, and devices that provide for stimulation of nerves and/or targets such as mechanoreceptors, tissue regions, mechanoresponsive proteins, and vascular targets through generation and delivery of mechanical vibrational waves. In certain embodiments, the approaches described herein utilize a stimulation device (e.g., a wearable device) for generation and delivery of the mechanical vibrational waves. As described herein, the delivered vibrational waves can be tailored based on particular targets (e.g., nerves, mechanoreceptors, vascular targets, tissue regions) to stimulate and/or to elicited particular desired responses in a subject.

Abstract: This disclosure includes several different features suitable for use in circumaural and supra-aural headphones designs. Designs that reduce the size of headphones and allow for small form-factor storage configurations are discussed. User convenience features that include synchronizing earpiece stem positions and automatically detecting the orientation of the headphones on a user's head are also discussed. Various power-saving features, design features, sensor configurations and user comfort features are also discussed.

Abstract: A facial protection equipment for an easy operation of rotating opening and closing, includes: a facial protection unit of which one side is supported at one side of a face of an operator and which shields and protects at least the one side of the face of the operator; a fixing unit that is worn on a head of the operator; and a connection member of which one end portion is coupled to one side of the fixing unit to be rotatable in an up-down direction and another end portion is coupled to the facial protection unit, where the connection member has a pivot bracket of which one end portion is coupled to the one side of the fixing unit to be rotatable in the up-down direction.

Abstract: An earmuff hearing-protection device (1) including a non-porous, sound-attenuating body (50) disposed within an interior space (31) defined by a shell (30) of an earmuff of the device, the non-porous, sound-attenuating body including sound-attenuating members (100) arranged and spaced to define a set of high aspect ratio air gaps (e.g. 300) between major side surfaces of neighboring members.

Abstract: This disclosure includes several different features suitable for use in circumaural and supra-aural headphones designs. Designs that reduce the size of headphones and allow for small form-factor storage configurations are discussed. User convenience features that include synchronizing earpiece stem positions and automatically detecting the orientation of the headphones on a user's head are also discussed. Various power-saving features, design features, sensor configurations and user comfort features are also discussed.

Abstract: A replaceable earmuff system with an arch-shaped member (headband) and first and second earmuff assemblies that are removably attached to the arch-shaped member. Each earmuff assembly has inner and outer earmuff housings and a spring. The inner earmuff housing is circular in shape with a flat base plate and a lip that extends around the perimeter of a first side of the inner earmuff housing. A circular protrusion, which has two opposing L-shaped slots, is situated in the center of the inner earmuff housing on a second side of the inner earmuff housing. The outer earmuff housing is saucer-shaped with a concave inner side and a convex outer side. A circular collar with two opposing keys that fit within the L-shaped slots is situated in the center of the concave inner side of the outer earmuff housing. The spring fits within the circular protrusion and the circular collar.

Abstract: A method and system is disclosed for a headset with force isolation, where the headset comprises a headband having two upper headband sections coupled by a center block and two ear cups, where each ear cup is coupled to one of the two upper headband sections. The two upper headband sections may include side support strips between which a movable strip may be placed, thereby increasing the rigidness of the headband when fully extended between the side support strips. The rigidness of the headband may decrease when the movable strips are retracted from between the side support strips and into the center block utilizing a slider knob. The side support strips may be plastic and the movable strip may be metal. The center block may be more rigid than the side support strips. The center block may be plastic. The headband may include headband endcaps at lower ends of the headband.

Abstract: A method and system for a headset with internal gimbal, where the headset comprises a headband, a headband, and ear cups coupled to the headband, wherein each ear cup may be coupled to the headband utilizing an internal gimbal. The internal gimbal may comprise a tip that is wider than its base. The tip may be rounded. The headband may comprise headband endcaps at each end of the headband. A headband slide may be coupled to each headband endcap. The headband ear cups may be coupled to the headband via the headband slides. Each headband slide may be coupled to a headband endcap via a headband pivot. The headband pivot may provide rotational motion of the ear cups with respect to the headband. The force on ears of a user of the headset may be spread evenly by the internal gimbals.

Abstract: A headphone includes: a headband; a sound emitter having a sound-emitting unit therein; and a connector connecting the sound emitter to the headband. The connector includes: a support for supporting the sound emitter so that the sound emitter is rotatable in a predetermined rotation range including a reference position; a restoring portion for applying a restoring force on the sound emitter for urging the sound emitter to return to the reference position; and a switcher for switching a state in which the restoring force acts on the sound emitter and a state in which the restoring force does not act on the sound emitter.

Abstract: The present invention is directed to earmuffs, and is intended to allow for hot packs to be used, thereby improving the effect of protecting ear regions from cold and a cold wave in the winter season. In order to achieve this, the present invention provides earmuffs (10) including a pair of ear covers (11) and a band (12) configured to connect the ear covers (11), wherein reception slots (13) through which hot packs (20) configured to generate heat are inserted and stored are formed in the ear covers (11), respectively.

Abstract: An air delivery system for providing a supply of air from a source of air at positive pressure to an interfacing structure located at the entrance to the airways of a patient includes a manifold adapted to connect with the supply of positive air pressure and at least one tube connected to the manifold and adapted to deliver the supply of air to the interfacing structure. Each tube is structured to allow movement between an open phase in which the tube allows the passage of air and a collapsed phase in which the tube is collapsed. Each tube is structured such that weight of a typical patient's head against bedding apparel is sufficient to collapse the tube from the open phase to the collapsed phase.

Abstract: An ear shield includes a lateral portion and a medial portion that are configured to respectively go over the lateral and medial sides of the auricle of a wearer's ear. The lateral and medial portions are joined together by a joining portion that acts as a cantilevered spring member, allowing the distal ends of the lateral and medial portions to move with respect to each other, but which biases the lateral and medial portions to a neutral position suitable for retaining the ear shield on a person's ear. There are articulating tabs further formed at the joining portion which extend to the rear, opposite the lateral and medial portions, that allow a user to move the lateral and medial portions relative to each other.

Abstract: An open audio device that includes an acoustic radiator that emits front-side acoustic radiation from its front side and emits rear-side acoustic radiation from its rear side, a front acoustic cavity that receives front-side acoustic radiation, a front transmission line that is acoustically coupled to the front acoustic cavity and comprises a first front sound-emitting opening, and a rear acoustic cavity that receives rear-side acoustic radiation and comprises at least a first rear sound-emitting opening.

Abstract: A protective cover device for an animal's head includes a first portion for securement around the animal's neck, behind the occiput and at or near the smallest diameter of the neck, and a second portion for covering the animal's ears that is fastened forward of said first portion and at or near the throat or jaw of the animal. The device may be a flexible/generally-flexible panel with supplemental shaping, stiffening, and/or adjustment systems to cup/fit the ears, to prevent the ears from sliding out of the device, and/or to prevent foreign objects such as cheat-grass or fox-tail, ticks, or insects from reaching the ears. Stiffeners may be added along or beside the central axis, around the front edge, and/or near the animal's ears, to shape and hold the second portion in a configuration protective of the animal ears and not easily rolled-up or pushed off by a paw/foot.

Abstract: A headphone device having an earcup that is configured to form a portion of an acoustic assembly of a headphone device. The earcup includes a seamless three-dimensional cover. The cover is formed from a continuous fabric of interlocking yarn. The cover can include portions having different performance characteristics, such as acoustic properties and/or comfort properties, that can be provided using different knit patterns and/or different fabric materials.

Abstract: A mask assembly adapted for use with a positive airway pressure device, includes a mask frame, an elbow assembly provided to the frame, a cushion provided to the frame, a forehead support assembly, and a neck to connect the frame to the forehead support assembly, wherein the neck includes a pair of side walls having a streamlined design that is made to look sleek and reduce or minimize obtrusiveness. The pair of side walls may take the form of a single wall or more than two walls. The mask frame may include a recessed port structure including at least one port having access to an interior of the frame which at least in part with the cushion defines a breathing chamber in communication with a nasal passage of the patient in use. The mask frame may also include a channel to receive the cushion. The channel is formed by an outer wall and an inner wall and the channel includes an inner surface having a bead to engage with an outer surface of an edge of the cushion.

Abstract: The present description provides an ear muff attachment assembly. An exemplary ear muff attachment assembly (100) includes a housing (110), an ear muff (130), an arm (120) having first and second end regions, the first end region positioned within the housing and the second end region attached to the ear muff, and a spring (150) engaged to the housing and the first end region of the arm. The arm is rotatable about a first axis of rotation between a first position and an intermediate position, and about a second axis of rotation between the intermediate position and a second position.

Abstract: An open audio device includes a housing and an acoustic radiator in the housing and that emits front-side acoustic radiation from its front side and emits rear-side acoustic radiation from its rear side. A front acoustic cavity in the housing receives front-side acoustic radiation, wherein the housing defines a front sound-emitting opening. A rear acoustic cavity in the housing that receives rear-side acoustic radiation, wherein the housing defines a rear sound-emitting opening. A support structure is configured to carry the housing on a user's head such that the housing is held proximate an ear of the user with one of the front or rear sound-emitting openings anterior of and proximate the tragus of the ear. The housing comprises an inner end that is configured to be closest to the user's head. The one of the front or rear sound-emitting openings that is anterior of and proximate the tragus of the ear lies at an angle to the inner end of the housing.

Abstract: Implementations of a ballistic helmet are provided. The ballistic helmet comprises two armor plates, each armor plate can be positioned to cover an ear of a wearer and thereby provide ballistic protection. In some implementations, the ballistic helmet may further comprise two earcup adapters, each earcup adapter is configured to be mounted on an interior side of an armor plate and to allow an attached earcup to rotate thereon. In this way, each earcup may be comfortably positioned over an ear of the wearer and thereby attenuate sound.

Abstract: A headband assembly that is constructed and arranged to be worn on or over a head of a user, having a curved compliant spring member, a cushion member that is configured to be in contact with or proximate the head of the user when the headband assembly is worn by the user, a spine that is coupled to both the cushion member and the spring member, and a cap that at least partially overlies the spring member and the spine.

Abstract: A headphone system, comprises a headset including two ear cups configured to output audio and including a headband coupled between the two ear cups, the headset including an outer casing having an outer casing shape, the outer casing shape covering the two ear cups and the headband, the outer casing shape including an outer casing periphery; and a headphone cover including a headphone cover shape, the headphone cover shape including a headphone cover periphery, the headphone cover including a clipping mechanism configured to interface with the outer casing at the outer casing periphery to enable the headphone cover to be removably attached to the headset, the headphone cover shape being similar to the outer casing shape, the headphone cover periphery being similar to the outer casing periphery.

Abstract: An example headset earcup adapter comprises: a housing that includes a clamp configured to secure about a stud of an earcup, a longitudinally extending bore configured to receive an arm of a headset wire form therein, an opening that extends through to the longitudinally extending bore, and a first protrusion and a second protrusion positioned above and below, respectively, an external entrance of the opening; a threaded insert positioned within the opening in the housing; and an adjustment screw threadedly received by the threaded insert that is long enough to extend through the threaded insert and into the longitudinally extending bore of the housing to make contact with an arm of a headset wire form positioned therein. The first protrusion and the second protrusion of the housing define an opening therebetween configured to receive the head portion of the adjustment screw therein.

Abstract: A headset in accordance with an embodiment of the present technology includes a headpiece, an earpiece, a yoke rotatably connected to the earpiece, and an arm extending between the yoke and the headpiece. The yoke at least partially defines a channel including a constriction at which a transverse cross-sectional area of the channel is non-circular. The arm includes a foot at least partially disposed within the channel. The foot is shaped to move through the constriction or be blocked from moving through the constriction depending on a rotational position of the arm relative to the yoke. The headset further includes a plug at least partially disposed within the channel. The plug restricts rotation of the arm relative to the yoke and thereby prevents movement of the foot out of the channel and corresponding separation of the arm from the yoke.

Abstract: A cover apparatus adapted to cover at least a portion of an ear for protection from the elements, artificial heat sources, and the like, is provided. Such a cover is produced in uniform structure such that any properly sized implement may be affixed to either a left or right ear. Additionally, the manner of affixing is provided through the provision of the ear cover exhibiting sufficient elasticity for pressure fitting around a subject ear auricle and lobe simultaneously, with lower levels of elasticity exhibited by the middle portion thereof extending between the top and bottom portions. Such a cover thus compresses for proper fitting around the auricle and lobe and does not provide excess pressure in the middle portion, thereby allowing for greater comfort and control to the wearer and leaves a least part of the wearer's ear canal exposed and uncovered to facilitate hearing while affixed.

Abstract: A hearing protector having an ear cup forming a space for a wearer's ear. The ear cup has a shell with an ear facing inner side and a passageway extending through the shell between the ear facing inner side and an outer side of the shell. The ear cup further has a loudspeaker assembly which seals the passageway from the outer side. The loud speaker assembly further has a seal member and a loudspeaker module. A portion of the seal member is arranged between the shell and a fastener, and the fastener retains the loudspeaker assembly at the shell. The hearing protector facilitates manufacturing and maintenance and provides for maximize wearing comfort and technical reliability.

Abstract: A headband assembly that is constructed and arranged to be worn on or over a head of a user, having a curved compliant spring member, a cushion member that is configured to be in contact with or proximate the head of the user when the headband assembly is worn by the user, a spine that is coupled to both the cushion member and the spring member, and a cap that at least partially overlies the spring member and the spine.

Abstract: A method and system for a headset with major and minor adjustments, where the headset comprises a headband, a headband endcap at each end of the headband, a headband slide coupled to each headband endcap, ear cups operatively coupled to the headband slides, and a floating headband coupled to the headband endcaps. A major adjustment of the headset may include actuating a headband slide in a vertical direction. The ear cups may be operatively coupled to the headband slides utilizing ball detents that may hold the position of the ear cups with respect to the headband slides. The ball detents may comprise a portion of a ball on the headband slide and holes in the ear cup or may comprise a portion of a ball in the ear cup and holes in the headband slide. Each headband slide may be coupled to a headband endcap via a headband pivot.

Abstract: A headphone device includes a head pad, a band, and a sleeve. The band extends from an edge of the head pad and supports a housing, via a hanger, housing a speaker unit at a tip of the band. The sleeve is slidable along the head pad and the band to adjust a length of a deformable part of the band.

Abstract: A method and system for a headset with internal gimbal, where the headset comprises a headband, a headband, and ear cups coupled to the headband, wherein each ear cup may be coupled to the headband utilizing an internal gimbal, which may comprise a gimbal post in an aperture. The gimbal post may comprise a tip that is wider than its base. The tip may be rounded. The headband may comprise headband endcaps at each end of the headband. A headband slide may be coupled to each headband endcap. The headband ear cups may be coupled to the headband via the headband slides. Each headband slide may be coupled to a headband endcap via a headband pivot. The headband pivot may provide rotational motion of the ear cups with respect to the headband. The force on ears of a user of the headset may be spread evenly by the internal gimbals.

Abstract: Embodiments of the present invention provide a head-mounted equipment. The head-mounted equipment includes an equipment body, an accessory and a connecting assembly implementing detachable connection between the accessory and the equipment body, where the connecting assembly is arranged on the accessory; the connecting assembly includes a buckle structure and a spring pressing structure. A clamping groove structure adapted to the buckle structure is provided on the equipment body. When the buckle structure is clamped into the clamping groove structure, the spring pressing structure contacts with the equipment body and applies an elastic force in a first direction to the equipment body. Under the action of the elastic force in the first direction, the buckle structure applies pressure in a second direction to the clamping groove structure; and the first direction is opposite to the second direction.

Abstract: A pivot-arm assembly is provided for attaching an ear cup to a mounting feature on an exterior of a helmet. The pivot-arm assembly comprises a mount configured to releasably couple to the mounting feature. A hinge is rotatable about a first axis and about a second axis. The hinge is coupled to a second end of the arm and disposed between the second end of the arm and the mount such that the first end of the arm is rotatable relative to the mount about the first axis and the first end of the arm is rotatable relative to the mount about the second axis. A biasing member is coupled to the arm and is configured to spring bias the first end of the arm relative to the mount in a rotatable direction about the second axis of the hinge.

Abstract: The disclosure is related to materials that includes phase change materials. The materials are suitable for use in acoustical devices such as headphones.

Abstract: An eyeglass headphone with a frame that is constructed and arranged to be carried by the head of a wearer, the frame comprising a bridge that is adapted to be supported by the wearer's nose, and a left temple and a right temple that extend rearwardly from the bridge, toward the left and right ears of the wearer, respectively, and a dipole loudspeaker built into the frame, where the dipole loudspeaker comprises a driver that emits front-side acoustic radiation from its front side, and emits rear-side acoustic radiation from its rear side. The frame comprises at least first and second sound-emitting openings, wherein the first sound-emitting opening is constructed and arranged to emit front-side acoustic radiation and the second sound-emitting opening is constructed and arranged to emit rear-side acoustic radiation.

Abstract: A personal acoustic system and flexible mount for the same are disclosed. The flexible mount is comprised of an elastomeric material. The personal acoustic system further includes a band comprising a first mount and an earpiece comprising a second mount. An acoustic element is housed within the earpiece. The elastomeric mount is positioned intermediate the first mount and the second mount to flexibly connect the band to the earpiece.

Abstract: The protective headgear of the present disclosure utilizes closed cell compression molded foam combined with mesh and hook and loop closures and elastic strap that allow the helmet to have a more custom fit than other protective headgear on the market. The three-point adjustment system allows the athlete to fit the size and shape of the headgear both horizontally and vertically to their particular head.

Abstract: An ear covering system for keeping ears warm while wearing earphones includes a pair of earphones. Each of the earphones is selectively worn in an associated one of a pair of ears. A pair of earmuffs is provided and each of the earmuffs is selectively worn on an associated one the ears. Each of the earmuffs has a hole therein and each of the earphones is selectively extended through the hole in an associated one of the earmuffs. In this way the earmuffs are worn in conjunction with the earphones. Each of the earmuffs is comprised of a fluid impermeable material to keep the ears warm in a cold environment.

Abstract: A headphone (3, 4) comprises a body (5) forming a chamber (26) for enclosing an ear of a user of the headphone (3, 4). The body (5) has an acoustic seal (7) of a flexible material surrounding the chamber (26), and the body (5) has a cushion (8) extending around the acoustic seal (7) and separate from the acoustic seal (7). The cushion (8) has a first side face (38) for engaging with the head of the user.

Abstract: An audio device with an acoustic radiator that emits acoustic radiation from a first side, a housing that defines an acoustic cavity that receives the acoustic radiation emitted from the first side of the acoustic radiator, and first and second sound-emitting outlets in the housing and acoustically coupled to the acoustic cavity such that the outlets emit sound from the acoustic cavity. The second sound-emitting outlet has a greater equivalent acoustic impedance than the first sound-emitting outlet.