Abstract: An exhaust end structure of a straight pneumatic wrench, including: a main body having a housing, at least one exhaust ports being formed on a wall of the housing for communicating an internal exhaust passage of the housing with outer atmosphere; and a tubular guide member, a first end of the guide member being connected with a section of the housing around the exhaust ports, whereby the exhaust ports only communicate with an interior of the tubular guide member.

Abstract: A sound attenuating system is provided for pneumatically powered surgical instruments. In one aspect, the exhaust hose is formed of at least two dissimilar materials to impede the transmission of vibrations or audible noise. In an alternative form, the exhaust hose has proximal and distal portions of dissimilar internal diameters.

Abstract: A noise reduction apparatus includes an intake passage forming member defining an intake passage, a resonator, and a vibration film. Intake air drawn into a combustion chamber of an internal combustion engine flows through the intake passage. The resonator has an inner volume part branching from the intake passage. The vibration film is placed to separate the intake passage from the inner volume part. The vibration film is vibrated by a sound pressure of a sound that is generated in the combustion chamber and that propagates through the intake passage. The vibration film has a projection part, which separates the vibration film into an inner vibration film part and an outer vibration film part.

Abstract: A system for reducing the vibration sensitivity of an implantable microphone without an equal or greater reduction in sound sensitivity. The system reduces non-ambient vibrations by placing at least one compliant member into the path of transmission for tissue-borne vibration, but not into the path for ambient sound-induced vibration. More particularly, a compliant member is interposed along the path between a source of non-ambient vibration and an implanted microphone. In one aspect, a compliant base member is disposed between an implanted microphone and an implant wearer's skull. In another aspect, a microphone is compliantly suspended relative to an implant housing using a support membrane. In either aspect, the compliant member (i.e., base member and/or membrane) and the supported member (i.e., housing and/or microphone) define a supported system having a natural or resonant frequency. This natural frequency may be set to a value to advantageously isolate the microphone against transmitted vibration.

Abstract: An implanted microphone is provided that has reduced sensitivity to vibration and attendant acceleration forces. In this regard, the microphone differentiates between the desirable and undesirable components of a transcutaneously received signal. More specifically, the present invention utilizes an output that is indicative of acceleration forces acting on the implanted microphone (e.g., an acceleration signal) to counteract and/or cancel the effects of acceleration induced pressures in an output signal of a microphone diaphragm. This may be done in a variety of ways, including but not limited to, pneumatically, mechanically, electrical analog, or digitally, or combinations thereof. In one arrangement, the generated output may be filtered to match the an acceleration response of the output signal of the microphone diaphragm such that upon removal of the motion signal from the microphone output, the remaining signal is an acoustic signal.

Abstract: A sound focus speaker adopting a gas-filled sound lens enhances efficiency of transferring sound from a source to target area and of protecting a spread of transferred sound. The sound focus speaker includes a gas-filled sound lens, sound sources for generating sound and a sound-absorption room for surrounding the sound lens and the sound sources. Sound emitted from the sound focus speaker is focused at specific distance to make a focus point and not spread to the outer of the focus point from forming a sound area.

Abstract: Ultrasonic transducers which include at least one internally directed generally concavely configured sonic energy radiating element which directs sonic energy toward at least one arcuate energy reflecting surface which redirects and focuses the energy through an opening in a housing defining the transducer. The configuration of the at least one radiating element and the at least one energy reflecting surface are such that sound waves from substantially any point along the radiating element to the reflecting surface and to a focus exteriorly of the opening are substantially equal. The transducers function to focus energy either as transmitters or receivers.

Abstract: The present invention comprises an ultrasonic resonant rod waveguide-radiator with at least three cylindrical sections, one of which is an entrance section having a planar entrance surface and another of which is an exit section having a planar exit surface, and at least two sections having a variable cross-section. The cylindrical sections and sections of variable cross-section are arranged in alternating fashion and connected to each other acoustically rigidly. The dimensions of the cylindrical sections and the sections of variable cross-section are selected so that the gain of the waveguide-radiator is significantly greater than unity and the strain created by passage of ultrasonic waves through the waveguide-radiator is minimized, increasing the operational life of the waveguide-radiator and maximizing the amount of useful energy transmitted by the waveguide-radiator.

Abstract: The germ and noise filter device is a disposable, hand held filter apparatus that covers the mouth of the user during the exhale phase of a cough. The device comprises: a body with a cavity that houses three micro-filters; a corrugated tube; two one-way valves and a mesh screen. The body can be made of durable plastic material that may be transparent or a combination of many attractive colors. The two one-way valves act as a filter element for the noise that would normally occur. An eyelet is formed on the body to allow the device to be worn about the person. When a cough is eminent, the opening of the device is engaged against the user lips to prevent the transmission of air-borne diseases and reduce the noise of the coughs.

Abstract: This invention has been made to provide a speaker system capable of miniaturization and presenting a good sound quality. A speaker 15 is mounted on a printed circuit board 21 arranged inside a telephone body enclosure 12. Acoustic waves of positive phase produced by vibration of a diaphragm 23 of the speaker 15 are output through front acoustic apertures 28 and a front air chamber 37 to the exterior from an enclosure acoustic aperture 13. On the other hand, the acoustic waves of opposite phase enter a rear air chamber 35 through rear acoustic apertures 29, reach an enclosure internal space 36 through an opposite-phase opening 34 provided by cutting away a part of a rear sealing member 32, and transmit to a card slot 14, then being output to the exterior.

Abstract: An acoustic resistor or damper and method of manufacturing the same is disclosed. The damper has mesh material and mounting material attached to the mesh material. The mounting material defines an open region for transmission of sound through the mesh material, and has a mounting surface for mounting the damper on a surface surrounding an acoustic port or tube. The mounting surface is located on a plane different from the mesh material, thereby shielding the mesh material from adhesive applied between the mounting surface and the surface surrounding the acoustic port or tube. The method of manufacturing an acoustic damper comprises exposing emulsion applied to a mesh material through at least one opening in a photographic mask to ultraviolet light and removing the emulsion exposed. A portion of the remaining emulsion and mesh material is cut in a shape surrounding the removed emulsion.

Abstract: An engine cover has a cover body having a through hole penetrating both sides of the cover body in an area opposed to a resonant space in which resonant sounds are generated. An opening of the through hole is covered with the sound absorbing member layer. Because a part of the resonant space is open, resonant sounds generated in the resonance space are decreased.

Abstract: An absorptive and reactive muffler includes an annular flow path for the gas with the center of the annulus having a plurality of resonators which are in open communication with the downstream end of the annular flow path and make up the reactive portion of the muffler. The flow path is at least partially lined by an absorptive material overlain by a perforate material and makes up the absorptive portion of the muffler.

Abstract: An acoustic waveguide system including a waveguide, a housing with a port in one side of the housing for receiving the proximal end of the waveguide, the port opening into a channel in the housing. A first shear transducer is located in the channel of the housing and disposed on the waveguide, and a second shear transducer is located in the channel and disposed on the opposite side of the waveguide. The first and second transducers are configured to launch a torsional or an extensional wave in the waveguide depending on the orientation and polarity of the transducers.

Abstract: An air introduction system (10) provides an active noise control system which includes a speaker assembly (28) in which the speaker support ring (36) is mounted to a speaker housing (32) without fasteners. In one speaker assembly, the speaker housing includes a plurality of extensions (40) which extend radially from an outer periphery of the speaker housing (32). The speaker support ring includes an edge (42) which at least partially surrounds the extensions (40). In another speaker assembly, the speaker support ring (50) includes a plurality of apertures (52) through a flange (54) which closely fits a speaker housing (32). The housing edge (54) and the speaker protection cone edge (56) are heated to a melting point of the material and the speaker support ring (50) is sandwiched therebetween. Heated material from the housing edge and the speaker protection cone edge pass through the apertures (52) to provide an effective bond therebetween.

Abstract: A soundproof cover includes a sealing layer, a sound insulation layer, and a vibration inhibition layer. The sound insulation layer has a peripheral portion, is to be disposed so as to contact at least the peripheral portion with a noise source, and exhibits elasticity. The sound insulation layer is formed as a hard plate shape, has an installation portion to be fastened to the noise source, and is disposed so as to cover the sealing layer. The vibration inhibition layer is disposed on at least a part of an interface between the sealing layer and the sound insulation layer so as to adhere to the sound insulation layer, and inhibits the sound insulation layer from vibrating.

Abstract: An arrangement for acoustically uncoupled mounting of slightly vibrating components on an anchoring part has a first sleeve which is adapted to guide through an opening of a component, a mounting screw which extends through the first sleeve, an uncoupling element adapted to be arranged between the component and the anchoring part, a second sleeve mounted coaxially to the first sleeve, a ring-shaped disc provided on each end of each of the sleeves, so that one of the discs is locatable between the anchoring part and the component at the other of the disc is locatable between the component and a head of the screw, the uncoupling element being adapted to be arranged between the component and a disc facing the anchoring part.

Abstract: In video equipment, a video equipment speaker device that is almost invisible from a viewer and capable of placing, toward the front of the center portion of the screen, an acoustic image from a speaker 2 provided on at least either an upper or lower portion of a screen is provided. A speaker device 1 includes the speaker 2, a sound duct 3 positioned forward of the speaker 2 to externally output sound, a speaker baffle 4 provided in the vicinity of edges forming an opening of the sound duct 3 and formed to outwardly reflect the sound, a fin 5 provided forward of the speaker baffle 4, sound space 6 formed between the speaker baffle 4 and the fin 5, and slits 7 outwardly opened from the sound space 6.

Abstract: A passive system for speech enhancement in a motor vehicle includes a headliner adapted to be disposed in an occupant compartment of the motor vehicle. The passive system also includes at least one passive sound reflector disposed in or near the headliner and being sound-reflective and shaped to direct or focus speech between front and rear seat occupants in the occupant compartment of the motor vehicle.

Abstract: The creation of sounds by musical instruments or sound reproduction systems is not perfect, but acoustic dissonances inherent in the production of sound generators can be corrected.

Abstract: A first feature of the present invention is that the opening of a sound output port 3b is smaller in area than the opening of a sound input port 3a in a horn 3. A second feature is that the sound output port 3b of the horn 3 is located so as not to be in the way of a center axis of sound radiation from a speaker 2. A third feature is that a length L of the horn 3 is set at 370 mm or below. A fourth feature is that the horn 3 is gradually narrowed such that vertical sections thereof from the sound input port 3a to the sound output port 3b respectively have areas based on a predetermined rule. Thus, it is possible to realize a speaker apparatus in which a sound output port of a horn is smaller in area than a vibrating surface of a speaker while reproducing sound whose quality is equal or similar to that in conventional speaker apparatus, and a television set equipped with the speaker apparatus.

Abstract: A laminated composite panel-form loudspeaker consists of a peripherally stiffened laminated composite radiating panel on which a preselected number of transducers are mounted and a rectangular frame carrying a flexible suspension device which supports the panel radiator. The laminated composite radiating panel comprises a predetermined number of orthotropic laminae with predetermined specific moduli and stacking sequence. The peripheral edge of the laminated composite radiating panel is reinforced with strips of which the rigidities are determined in such a way that beneficial natural normal modes of the radiating panel are excited and satisfactory operation of the panel radiator over a desired acoustic frequency range achieved. The standing waves at the peripheral edge of the stiffened radiating panel are damped out via the use of the flexible suspension device.

Abstract: An apparatus for the redistribution of acoustic energy is provided which comprises a lens having a reflective surface defined by the surface of revolution (R1) of an elliptical arc (A1) rotated about a line (L) through an angle (&agr;1) and the surface of revolution (R2) of an elliptical arc (A2) rotated about the line (L) through an angle (&agr;2). Each elliptical arc (A1) and (A2) constitutes a portion of an ellipse (E1) or (E2) having a focal point located at a point (F1) on line (L), and shares an end point (P) which lies on the reflective surface and the line (L). The angle (&agr;1) is chosen such that the surface of revolution (R1) is convex with respect to an adjoining surface (S1) and the angle (&agr;2) is chosen such that the surface of revolution (R2) is concave with respect to the adjoining surface (S1).

Abstract: A fiber body includes a collection of fibers containing thermoplastic resin as the main component and an energy consuming component, such as a piezoelectric material for converting and consuming external mechanical energy of sound and vibration. The energy is converted into electrical energy, which in turn, is converted and consumed into and as heat by means of the electrical resistance of the resin.

Abstract: A method is provided for managing the energy usage of an energy consuming system adapted to determine the energy of a controlled space, the energy consuming system including a plurality of operating components having on and off states and a plurality of differing noise levels when making transitions between the on and off states. The method includes determining the noise levels of the components of the energy consuming system, selecting a relatively low noise level component of the energy consuming system to provide a selected noise masking component, and causing a relatively high noise level component of the energy consuming system differing from the selected noise masking component to make a transition between on and off states. The method further includes causing the selected noise masking component to make a transition between its on and off states after the transition of high noise level component.

Abstract: A vibration damped structure, which is excellent in vibration absorption and sound absorption effect, is provided by coating the surface of a structure to be damped with a mixture of molten photopolymerizable resin and a photopolymerization initiator and then subjecting the coated surface to irradiation, whereby a vibration damping coating is formed on said surface.

Abstract: An adjustable speaker system includes a speaker enclosure having at least a forward facing surface, the speaker enclosure enclosing a speaker with a forward facing acoustic outlet from which sound may emanate in a forward direction. The system further includes at least one reflector, and preferably a pair of independently adjustable reflectors, with a sound-reflecting rearward facing surface, each reflector being pivotably secured adjacent the acoustic outlet and pivotable relative to the acoustic outlet between a non-reflecting orientation wherein the sound-reflecting rearward facing surface is substantially in alignment with the forward direction, thereby to only minimally reflect sound emanating from the acoustic outlet, and a reflecting orientation wherein the sound-reflecting rearward facing surface is substantially angled to the forward direction, thereby reflecting impinging sound emanating from the acoustic outlet laterally to a respective side.

Abstract: A window-type air conditioner housing includes a backboard and two parietal sideboards of polystyrene. Each sideboard has a steel plate implant and a coaxial bracing hole for supporting a motor and an associated air conditioner fan bearing components, respectively, to thereby maintain vibration and noise at reduced levels. Preferably each steel plate implant is dimpled in the area surrounding each coaxial bracing hole to strengthen and stiffen the sideboard in that area for supporting the motor and fan assembly.

Abstract: An apparatus for the redistribution of acoustic energy is provided which comprises a lens having a reflective surface defined by the surface of revolution R1 of an elliptical arc A1 rotated about a line L through an angle .alpha.1 and the surface of revolution R2 of an elliptical arc A2 rotated about the line L through an angle .alpha.2. Each elliptical arc A1 and A2 constitutes a portion of an ellipse E1 or E2 having a focal point located at a point F1 on line L, and shares an end point P which lies on the reflective surface and the line L. The angle .alpha.1 is chosen such that the surface of revolution R1 is convex with respect to an adjoining surface S1 and the angle .alpha.2 is chosen such that the surface of revolution R2 is concave with respect to the adjoining surface S1.

Abstract: A loudspeaker horn has straight wall section and a curved wall section. The straight wall section has diverging walls defining a coverage angle and the curved wall portion is connected to the straight wall portion at a point tangent thereto, and has a proximal end disposed perpendicular to the plane of the throat entrance. At least one coverage angle in orthogonal planes has a common apex in the plane of the throat entrance and along the horn axis.

Abstract: An easily-combinable and movable speaker case includes two side boards, a front holed board, a speaker support board, an electric circuit board, a rear control board, a cap board, a bottom board, and a pull member. The two side boards are spaced apart parallel and respectively has a plurality of vertical position grooves and posts spaced apart on an inner surface for inserting the front holes board, the speaker support board, the electric circuit board and the control board in the position grooves of the two side board. Then the cap board and the bottom board are respectively fixed on and under the two side boards with screws. Further two rollers are fixed under the bottom board to permit the speaker case inclinedly move on the ground by pulling the pull member.

Abstract: In a sound generator of the type having a motor powered piston (7-9) limiting a chamber (18) connected to a resonance tube (16) and which is adapted to generate sound waves for cleaning heat exchange surfaces, the piston (7-9) is according the invention provided with two axially spaced piston membranes (8, 9) and a device (19) for establishing a vacuum between the two membranes (8, 9) and thus ensuring only tensile stresses in membranes (8, 9) thereby increasing their life time.

Abstract: An acoustic lens device is provided for use in facilitating oral communication in a space which is acoustically challenged. The lens device includes at least one acoustic reflector for positioning proximate to a dashboard of a passenger portion of a transport vehicle. The reflector is formed by an upper portion with an ellipsoidal surface obtained when an ellipse having two foci on an axis extending in a substantially vertical direction is rotated about the axis. In consequence, the upper portion encloses at least one of the two foci such that each of the at least one reflectors is disposed at a predetermined distance from the other with parallel axes. The first loci is disposed such that voice signals emitted from the mouths of persons seated in the front passenger compartment are directed from the first foci to the device. Accordingly, a sound pressure of a voice signal reaches the axis of the at least one reflector and is focused by the device and directed to the second focus in the back passenger portion.

Abstract: A sound-transmissive cover assembly which provides protection from the ambient environment to transducers such as microphones, loudspeakers, buzzers, ringers, and other delicate devices; and across which sound energy can pass with very low attenuation. The cover assembly has a protective membrane layer and a porous support material layer which are selectively bonded together at least in the outer region near their edges. An inner unbonded region surrounded by the bonded outer region is provided so that the protective membrane and porous support layer can vibrate or move independently in response to acoustic energy passing through them. An embodiment of the assembly includes at least one acoustic gasket attached to one or both of the layers so as to not impede independent movement of the layers.

Abstract: In general, the invention comprises a device capable of emitting either acoustic or electromagnetic radiant energy. The device has at least one reflector with a smooth concave surface which reflects the energy emitted from the transducing element. The device also has at least two transducing elements for producing this energy. The shape of this reflector surface is preferably defined by either an ellipse or a parabola that is rotated about an axis of revolution, for any angular distance between zero and one complete revolution. The shape of this reflector surface can also be preferably defined by the coincident surfaces of revolution of an ellipse and a parabola that are rotated about a common axis of revolution.

Abstract: The acoustic noise monitor determines acoustic sound levels radiated or stered to an exterior or interior fluid space of a structure such as an enclosed structure by measuring a condition, such as strain level, of the structure itself rather than by directly measuring the fluid itself. From the strain or other condition measured on the structure, the acoustic sound levels can be calculated with the Helmholtz integral. The sensors on the structure are preferably spaced so that non-radiating high wave-number motions of the structure are averaged out. The acoustic noise monitor can be used with submarines, jet aircraft, cars, or the like.

Abstract: In a speaker grille formed of a synthetic resin, including a grille plate having a plurality of through holes and a frame integrally formed with the grille plate so as to surround the outer periphery of the grille plate, a ring-shaped groove is formed between the grille plate and the frame so as to extend along the inner periphery of the frame. In molding the speaker grille, the flow of the resin is blocked by a ring-shaped dam provided in a metal mold to form the ring-shaped groove. Accordingly, the speaker grille can be beautifully molded without the generation of appearance defects such as flow mark, weld, and short. Further, in forming through holes also at the boundary between the grille plate and the frame, there is no problem in strength of the metal mold.

Abstract: In general, the invention comprises a device capable of emitting either acoustic or electromagnetic radiant energy. The device has at least two transducing elements for producing this energy, and at least one reflector which reflects the energy emitted from the transducing elements. The shape of the reflector surface is defined by both an ellipse and a parabola that are rotated coincidentally about a common axis of revolution (hereinafter referred to as a "para-elliptic" reflector surface), formed by coincidentally rotating, for up to one complete revolution, a section of both geometric shapes about an common axis of revolution that lies in the plane of both geometric shapes. The resulting "para-elliptic" reflector surface will be characterized by two sets of distinct focal points defining two focal curves. Focused energy will be redirected as if emanating from each focal region, causing each focal region to appear as a virtual source of the energy.

Abstract: The invention relates to a method and apparatus for the generation of low frequency sound by means of the excitation of a low frequency standing gas borne sound wave. A low frequency sound generator comprises a resonator part and a feeder part with a feeder unit. The method consists of a controlled generation of periodic changes of the gas volume of the resonator part in order to create a standing sound wave. The invention also includes a feeder unit for the working of the method. The feeder unit comprised of three rotating parts, namely one center rotor and two side rotors, the rotation of which are synchronized. The feeder unit is open on two sides, each side communicating with one tubular resonator. The rotors are provided with cut out portions and the center rotor is also provided with a protruding vane-shaped part.

Abstract: A microphone, preferably of the type to be held in the hand or to be attached to a stand, includes a handle part, an intermediate part and a head part. At least the handle part is formed of two halves, each of which is symmetrical about a plane extending through the longitudinal axis of the handle part.

Abstract: An ultrasonic transducer is described that comprises an oscillatory element (e.g., piezoelectric or electrostatic) having a frequency of oscillation in the ultrasonic region. The transducer includes a conical diaphragm connected at its apex to the center of the oscillatory element. The diaphragm has a rim which defines a concave opening and is responsive to an actuation of the oscillatory element to generate a plane wave in the direction of the concave opening. A faceplate having a small aperture abuts the rim of the conical diaphragm. The diaphragm is concentrically positioned with respect to the aperture and is bonded to the faceplate by a flexible adhesive. An induced plane wave is thereby diffracted by the aperturre and exits therefrom with a substantially omnidirectional beam pattern.

Abstract: A sound focusing device for use with a siren. The device is comprised of an adjustable baffle or damper reducing the velocity of air or sound eminating from a siren. The baffle or damper is positioned internal to the siren. A conical sound focusing trumpet is positioned co-axially and external to the siren. The baffle or damper is made up of two complementary disks forming at least one defined opening therein. The baffle or damper is selectively adjustable.

Abstract: A loudspeaker assembly includes a vibrating element which generates pressure waves in a first predetermined frequency range which propagate in a first forward direction and a second backward direction. A driver drives the vibrating element. A first diffuser uniformly diffuses the forward waves. A tuner selects back waves in a second predetermined frequency range within said first predetermined frequency range. The tuner includes a second diffuser for diffusing the back waves within said second frequency range such that the selected back waves and the front waves are in phase.

Abstract: This invention relates to the use of a flexible, heat resistant mold member. The mold member is useful in molding processes such as dip or slush molding. The mold member maintains its structural integrity and may therefore be used as an insert in the article being molded to provide flexible stability at specific locations within the article. The mold member is made of a material which is substantially non-reactive with the molded article. The molded article may be any article made from a plastisol such as a binaural for a stethoscope having single or double lumens.

Abstract: An ultrasonic sensor which is particularly suited to measuring the sound-pressure amplitude in the focus range of a lithotripter and includes in a region a piezoelectrically activated polymeric foil, which is coupled to electrodes. The polymeric foil is mounted in a housing, which has a convex curved, dome-shaped surface at least in one region located opposite one of the flat sides of the polymeric foil. A simple measurement of the sonic field is thus made possible directly on the rubber-diaphragm encased, water-filled delay path of the lithotripter.

Abstract: An audible sound radiated from an air conditioning apparatus is decreased when the actual audible sound detected by the sound sensor is greater than a predetermined audible sound value which is modified according to changes in the ambient light or the ambient temperature.

Abstract: A speaker including a speaker unit, a speaker frame for supporting the speaker unit and a grille unit for covering the speaker frame. The grille unit is bolted to the speaker frame by bolts, and the grille unit includes flaps for covering head portions of the bolts used for bolting the grille unit to the speaker frame.

Abstract: An acoustic filter is provided for attenuating or suppressing the negative pressure half-waves of an elastic wave, comprising an enclosure containing a liquid whose saturating vapor tension is close to the atmospheric pressure. A pump causes the liquid to flow and a regulator fixes its temperature.

Abstract: A frameless pierced metal speaker grille is directly attached to a panel in which a speaker opening is formed by a series of tabs integrally formed in the speaker grille at spaced locations about the perimeter of the grille. Each tab includes a rear facing planar section extending inwardly from a turned edge perimeter of the cover grille and abutted against the panel structure, a v shaped engagement section extending rearwardly from the planar section and having legs adapted to squeeze fit the panel edge adjacent the speaker opening, and an entry section extending rearwardly from the v section and inclined inwardly to cam the tab inwardly at assembly of the grille. The tab shape enables secure spring fitting to the panel structure while being formed of the relatively mild material of the grille material which is pierced as by being perforated to form the open area cover grille.

Abstract: A speaker and horn array having improved audio characteristics is formed in a baffle case. A plurality of small speakers are mounted in the baffle case in a vertical array in close proximity with one another. Each of the speakers has an acoustic baffle over the back of the speaker with an opening located in the baffle. An array of small horns are located in association with the speakers in the baffle case. As with the speakers the horns are also in a vertical array. Each of the horns includes an individual throat, however, all of the horns are joined into a common vertically oriented mouth. The throat of each horn is connected to the opening in the baffle of one of the speakers. This backloads the individual speakers with the common mouth of each of the horns resulting in common backloading of each of the speakers.