Abstract: The acoustic tower of the present invention is a portable, acoustic tower that has both a performance position and a storage position. In the storage position, a canopy panel lies substantially parallel proximate an upper panel, both of which are hingedly secured to a cross tube assembly that is supported by a lift tube. The upper panel lies substantially parallel to a lower panel that is fixedly secured to a lower panel assembly having side supports and a center shaft which substantially contains the lift tube. To raise the acoustic tower to the performance position, the canopy panel is raised to one of a plurality of preset angles and maintained in position through use of ratchet and pawl assemblies of the cross tube assembly. With the canopy panel at the desired angle, the upper panel and canopy panel are raised vertically by telescopically elevating the lift tube within the center shaft. The lift tube is elevated by virtue of a winch assembly that is connected to the lift tube by a length of webbing.

Abstract: An upper housing shell of a hermetically sealed refrigeration compressor has a central asymmetrical section interposed between a lower cylindrical section and an upper spherical section. The shape of the central section is such that opposite points define a line that is perpendicular to the surface at one point, but is not perpendicular to the surface at the opposite point.

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: Loudspeaker improvements are disclosed to add versatility and economy, particularly for multimedia applications. These improvements include: (1) the printing of voice coil conductors, (2) adding conductive elements to the sound driver surface, (3) using multiple coil paths around a single voice coil former to drive the overall sound driver surface, (4) creating a simple digital loudspeaker with multiple coil paths, (5) implementing multiple functions in the multiple coil loudspeaker/transducer, (6) creating integrated systems with a series of multiple function, multiple coil loudspeakers/transducers and (7) providing a novel subwoofer loudspeaker housed in a cylinder.

Abstract: A jet engine test cell capable of dissipating infrasound. The test cell includes an engine test section, an augmentor and an exhaust stack having a structure near its open end for dissipating infrasound.

Abstract: An acoustic sensing means such as a microphone or a thin-film sensor is located in a flowing medium. To prevent the sensing of flow generated noise, the sensing means is separated from the flowing medium by at least three stages of shielding. In a preferred embodiment, the sensing means is located within a foam shield which is located in a frame covered by a fabric shield and which is, in turn, located in a second frame covered by a second fabric shield. A spandex fabric is suitable for use in the present invention.

Abstract: A hydraulic unit having a hollow oil container which has a receiving space for oil between an external outer wall and an internal outer wall, and having a pump unit which comprises an electric motor and a pump which can be driven by the electric motor. Such a hydraulic unit is to be further developed in such a manner that it has only a low noise level, in which connection also sufficient cooling of the hydraulic fluid and of the electric motor should be assured. This is achieved in the manner that at least the pump, and preferably the pump unit, is included in an enclosure which is formed by the hollow oil container and at least one sound-damping element.

Abstract: An appliance muffling device for reducing noise and vibrations produced by conventional appliances, such as blenders, comprising a uniform cover connectable to a uniform base enclosure both preferably having side walls where a connection is made through snapping engagement so as to form an interior volume for enclosing an appliance, wherein the switch or switches of the appliance are engageable by a slidable switch engaging member assembled on opposite sides of the base side walls through an aperture defined by the base side walls. The appliance muffling device further comprises a ventilating system including an air intake chamber, for receiving ambient air from a plurality of air intake channels defined by the base in communication therewith, and an exhaust channel separate and independent from the air intake chamber for exhausting heat produced and emitted by the enclosed appliance.

Abstract: A method of using a material as an acoustical barrier in an ambient medium. The material comprises microbubbles having average outer diameters of 5 to 150 microns, bound together at their contact points. The material is characterized by either a porosity of 20 to 60 percent, or by voids between the microbubbles which have characteristic diameter within an order of magnitude of the viscous skin depth of the ambient medium, as calculated at 1 kHz; an air flow resistivity of 0.5.times.10.sup.4 to 4.times.10.sup.7 mks rayls/meter, and an attenuation of sound comparable to mass law performance. The microbubbles can be sintered into direct contact with each other, or one of many types of binder material can be used to support the microbubbles within a composite material.

Abstract: A housing lining for a piston engine, drive motor, or machine composed of a sound-absorbent layer of fibers. The fibers are compressed and glued to form an essentially pore-free supporting frame at least in the vicinity of the edge of the layer.

Abstract: This invention relates to electro-acoustic transducers such as is generally indicated at 10 and which comprise a body 11 defining a chamber 12, a plate 13 bearing a micro-phone or speaker 14 to which is attached a stalk 15, a diaphragm 16, connectable to the stalk 15, which extends substantially across the chamber 12, an end piece 17 and an end cap 18. The end piece 17 has a kidney-shaped recess 21 which provides the main communication path between subsidiary inlets/outlets 19 and a main inlet/outlet 20. When the channel 22 is closed off by the end cap 18 it is effectively in the form of a tube and constitutes a Thuras tube. The length of this path effectively creates a long discharge path between the wearers' ear and any grounded metal part within the transducer and hence protects against electric shock.

Abstract: An acoustically advanced infant incubator housing system of special value for helicopter transport. This system is comprised of an ovally shaped infant housing using double wall construction with an air space between them supported on a cradle suspension system. This process creates a superior noise and vibration rejection system, providing for a quiet chamber interior.

Abstract: An appliance muffler for absorbing sound wave vibrations and impact from foreign objects employed to muffle noise transmissions produced by the appliance and to protect the outer surface of the appliance, wherein the appliance muffler comprises a flexible appliance jacket mounted over the appliance base and a flexible and stretchable appliance container sleeve mounted over the container.

Abstract: Synthetic sponge or other resilient material is joined to the top of a room air-conditioner to absorb the physical impact of rain and dripping water to inhibit the creation of the noise that would otherwise occur. Additionally, a buffer formed with angular surfaces, to absorb and deflect the full impact of rain and dripping water to inhibit the creation of noise that would otherwise occur.

Abstract: A low noise type reduction gear which assures that sound generated by collision of particles of a lubricant with a wall surface of a casing and sound attributable to resonance of the casing can substantially be attenuated by arranging laminated vibration damping steel sheets inside of the casing.

Abstract: The horn housing may comprise an inner metal shell in the shape of a hexagonal box open at one end fitting into a similarly shaped outer dense solid box similarly open at one end. Space between the inner and the outer boxes being filled by a low density sound absorbing filler, and the inner box being connected to the outer box by vibration absorbing bolts. The outer box is mounted to a structure by vibration absorbing mounting brackets. When a high decibel horn or siren is mounted in the inner box to directed sound through the opening, most of the sound propagating sideways towards the structure is absorbed by the housing increasing the comfort level of passengers or crew inside the structure.

Abstract: Heat shrink tubing is disposed about a pneumatic tool and heat shrunk into position on the tool. Foraminous material is located between the tubing and tool in a restricted fluid-flow passageway extending between a tool air flow outlet and an end of the heat shrunk tubing.

Abstract: Material for providing acoustic protection against a source of noise, the material comprising a substrate and resonators, wherein said resonators formed on the substrate are constituted by thread-like and/or area-occupying composite elements whose structural characteristics (density, modulus of elasticity, shear modulus, damping factor, piezoelectric factor, etc. ...) and whose shape and/or size are selected to associate a predetermined resonant frequency with each resonator, and also to absorb the sound pressure energy from the noise source at said resonant frequency and dissipate it in the form of mechanical heat energy and/or electrical energy. The invention also relates to apparatus constituted by a wall including at least one layer of the above material.

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: A muffler cover formed in such a manner that joint sections having a relatively small width are located between a front portion and a top portion, between the front portion and a left side portion, and between the front portion and a right side portion, and that extension sections having substantially the same width as the joint sections are located on both sides of the top portion, the joint sections and the extension sections being folded at an angle of substantially 45 degrees.

Abstract: A laminate acoustic window for sonar systems having a pair of septa sandwiching a core therebetween, the core being made of a low shear high elongation to break material, the septa being formed of a relatively low density, high modulus material. The windows of the invention are characterizied by unusual freedom from attenuation loss over a wide frequency range. The windows are further substantially self damping and avoid thereby a generation of significant quantities of deleterious noise due to self generated vibration and transmitted vibration.

Abstract: Gas liquid mixtures readily absorb the wave energy of noise and thus reduce noise intensity. By circulating gas liquid mixtures through jackets surrounding noisy machines, such as internal combustion engines, undesirable noise can be reduced.

Abstract: An armored self-contained outdoor/indoor siren assembly which eliminates the need for an additional protective box and an additional tamper switch which are generally used in the prior art installations. The armored siren assembly of the invention consists of a rigid and strong cover member which forms a housing, and a number of horns mounted within the housing in coaxial nested relationshp with one another which not only form a sound chamber for the siren, but also form a protective means for the sound generating unit of the siren to prevent access to the sound generating unit by unauthorized persons. The cover of the assembly, as well as the various horns included in the housing, and the mounting brackets for the horns, may all be formed, for example, of rustproof diecast aluminum.

Abstract: A vehicle warning system (1) is disclosed. The device includes a main housing (2) to which is attached a sound generator (7), a lighting system (5), a mounting bracket (4) which is used to attach the device to an emergency vehicle, and a trim ring (6) which conceals the mounting means of the device. As a sound signal is produced by the generator (7) it passes through a nozzle (9) and an aperture (14) into a deflector means (3) which is designed to expand and direct the sound signal through carefully proportioned chambers (30) and (33) of the deflector (3) so as to direct the sound signal against the closed portion (15) of expander horn (16) and out the open portion of the expander horn (16). In operation the sound generating system is attached to an amplifier of well known design and is capable of producing a variety of sound signals.

Abstract: A housing adapted for receiving a sonic transducer capable of projecting and receiving a sonic pattern having a primary lobe and a secondary lobe. The housing has an end wall for receiving the sonic transducer and a restrictive wall for intercepting the secondary lobe of the sonic pattern in one quadrant and reflecting that portion of the secondary lobe into the opposite quadrant. A pair of side walls substantially intercept and reflect the secondary lobe in quadrants adjacent the one quardant to provide more uniform sonic pattern. The side walls may be disposed at an angle outward from the direction of projection of the primary lobe having a value of from 0.2 to 0.3 of the value of the angle the secondary lobe makes with the primary lobe.

Abstract: A housing for enclosing motorized appliances consists of a structure constructed of noise absorbing materials. A door on the housing, when closed, activates internal circuitry for supplying power to the enclosed appliance. The housing absorbs much of the noise generated during operation of the appliance, allowing conversation and entertainment to continue in a normal manner without noise interruption from the appliance.

Abstract: Disclosed herein is an improved sound absorbing diffusor device wherein the surface designed to face the sound source includes a plurality of sound absorbing wells of equal widths but different depths separated by thin sound absorbing dividers. The depths of the individual wells are based upon the quadratic-residue number theory sequence which is used in acoustic design. The wells are covered with an open weave fabric adhered thereover which fabric is specifically chosen for its ability to allow sound to pass therethorugh to the wells and dividers. Tests performed on the inventive sound absorbing diffusor have revealed significant reduction in sound levels of reflected sounds over that which would accrue from a flat absorptive panel.

Abstract: An acoustic damper for substantially reducing the reverberation echoes at the junction between an acoustic signal propagating fluid and a material having an acoustic impedance substantially different from that of the fluid. The damper, which is particularly adapted for use in ultrasonic transducers, is formed of a material having an acoustic impedance which substantially matches the acoustic impedance of the fluid, such material preferably being a foam plastic material having sufficient hardness to be acoustically stable. For preferred embodiments, the damper is formed of a laminate of the layer described above and a second layer of a material which provides high acoustic attenuation, such as cork material.

Abstract: A baffle for use in baffling or reflecting acoustic frequencies in a marine environment wherein a core ply of fiber or fabric reinforced rubber sheet is sandwiched between a pair of plies formed of an elastomeric substance and having fluid filled pockets embeddedly positioned therein in a regular, spaced relationship. The reflector functions to baffle or reflect undesired acoustic frequencies typically in conjunction with the operation of sonar arrays.

Abstract: A blow-off nozzle assembly provides protection for users, without increasing the noise level, and also protects the nozzle from breakage if dropped. A circular cross-section rod assumes an oblong configuration defining an oblong shaped opening, with circular cross-section support posts extending from one side of the rod. The support posts are received by a casing having channels on opposite sides of a linear array of individual jets of a multi-channel substantially flat jet nozzle. The oblong shaped guard is mounted so that it is spaced from the nozzle in the direction of air flow from the nozzle with a linear array of jets centered within a geometric projection of the opening. The guard prevents deadending, so that the pressure of compressed air if the guard were pressed against a worker's skin would be below the OSHA standard of 30 p.s.i.

Abstract: A low drag warning system for emergency vehicles having an aerodynamic design reducing turbulent flow past the housing for increased fuel economy and performance. The housing of the warning light system is provided with a pair of light globe compartments possessing an efficient aerodynamic design and a central speaker housing. The speaker housing has a downward sloped speaker grill to create a flow pattern also reducing drag. The air flow is introduced into the speaker housing with a ram effect. Outflow ports from the speaker housing circulate an air flow within the domes to prevent condensation and cool the components therein. The speaker mounted in the housing attains increased sound output using a relatively low power drive.

Abstract: A board having improved thermal and/or acoustical properties is disclosed, together with a method and apparatus for producing same. The board is of finite thickness and has a graduated density, the two opposing major surfaces have the greatest density and the intermediate portion has the least density with the board density gradually decreasing in the region between the major surfaces toward the intermediate portion thereof. The board is produced by a molding process, wherein blankets of loosely gathered fibers and containing a suitable binder, are utilized to form the board. The blankets are preferably high compressible and have interposed therebetween an initially relatively highly incompressible air filled member. These laminates are pressed together between a pair of heated mold halves. As the temperature of the laminate increases, the interposed member softens and is rapidly reduced in thickness due to the escape of air as it softens and melts.

Abstract: An underwater voice communicator in which the preferred embodiment comprises a pair of tapered tubes in communication with a diver's mouth. The tubes are constructed of a material having a sound impedance similar to the sound impedance of water. Sound energy issuing from the mouth of a diver is reflected down the length of the tapered tubes to an area of the tube that concentrates the sound for injection into the surrounding water.

Abstract: A bubble silencer for use with scuba equipment is comprised of a flat flexible enclosure attached to a scuba regulator valve. Exhaust bubbles issuing from the regulator into the enclosure coalesce into large air parcels to be expelled at low velocity through a rearward exit port. The large size and low velocity of the exhaust bubbles leaving the enclosure are much quieter than the small high velocity bubbles issuing from the regulator itself.

Abstract: A high pressure gas flare using the Coanda effect has a noise attenuator surrounding the high pressure gas outlet slot. The noise attenuator is in the form of one or more upwardly diverging frusto-conical shields which may be spaced apart or closed with the body of the flare. The attenuator is particularly useful for steam driven flares.

Abstract: It should be possible to manufacture, in a simple manner, a sound-absorbing wall-lining (3) consisting of a material to be applied to the wall which needs lining, and a resilient layer (4, 5) of foam, e.g. foam rubber, felt, or similar material, having locally distinctive sound-absorbing capacities, and whose thickness will possibly remain uniform, provided the resilient layer (4, 5) contains a filler with locally distinctive degrees of cross-linking--corresponding to distinctive sound-absorbing capacities.

Abstract: Acoustic intensity measuring apparatus for determining sound energy intensity utilizing a probe having a pair of microphones and an associated ambient noise shield.

Abstract: A structure for decreasing low frequency air vibrations, comprising a sound insulating floor, sound insulating sidewalls and a sound absorbing ceiling arranged so as to form an air chamber below and separate from the underside of an elevated road or railway bridge's traversed surface, thereby forming a space between the sound absorbing ceiling and the elevated bridge. The structure is very effective for decreasing the low frequency air vibration emanating from the structure of the elevated bridge and the low frequency air vibrations transmitted from the structural supports of the elevated bridge.

Abstract: A microphone holding device which holds a microphone in a casing so that the microphone is disposed substantially perpendicularly to the surface of a concave of a helmet, etc. for receiving the microphone in it. Thus, both the sound collecting portion and the opposed end of the microphone are kept freely communicated with the outside of the casing.

Abstract: An exhaust muffler cover for internal combustion engines having a piled buffering layer provided on the outer surface of a cover member surrounding the exhaust muffler body with a suitable gap therebetween. The cover member has a sufficiently reduced thickness to ensure a good radiation of the heat transmitted from the exhaust muffler body. An attaching member playing the role of a reinforcement is fixed to the inner peripheral end of the cover member.

Abstract: A miniature sounder having a diaphragm closing one end of a tuned chamber. The other end of the chamber communicates with the interior of a tuned housing. The chamber and housing are both tuned to the desired oscillating frequency of the diaphragm with the chamber resonant frequency comprising substantially three times the desired frequency and twice the housing resonant frequency.

Abstract: An anechoic chamber having a rotatable corner in the nature of a rotating door which permits the selection of a desired one of four right angle corners to be introduced into operative engagement with the room. In the use of the anechoic chamber, with a selected corner in position facing into the chamber, a sound seal is provided about the periphery of the frame of the rotating door. The walls of the anechoic chamber are covered by sound absorbent material, and one of the four corners which may be positioned in the chamber through rotation of the rotating door contains surfaces similarly covered by sound absorbent material. Another of the four corners is a trihedral corner including a base, or floor, for supporting a corner speaker.

Abstract: A sound room having sound wave reflective front and side walls, and ceiling and a sound absorbent floor and rear wall arranged to form a wedge shaped room. Sound generating speakers are positioned at the upper front wall forming the small end of the wedge shaped room so that sound waves emanating therefrom will expand outwardly to fill the room.

Abstract: A passive system having high volumetric compliance in response to compressions and expansions, such as are present in low frequency acoustic wave energy, employs a saturated vapor-saturated liquid interface thermodynamically stabilized by distributed heat sinks that interact with the acoustic wave energy. The volumetric compliance of a system, such as a loudspeaker enclosure, is significantly increased by utilizing a spatially distributed mass of fine fibers thoroughly wetted by a liquid, to provide thin liquid sheaths on the fibers that are in good thermal interchange with the fibers themselves and also with the vapor molecules in the spaces between the fibers. The liquid preferably has a low heat of vaporization, a high vapor pressure at the ambient temperature and a low rate of pressure change with respect to temperature. The liquid sheaths and fibers serve as high surface area heat sinks having a short thermal transport distance to supply the alternating heat attendant to evaporation and condensation.

Abstract: Noise attenuation during the purging of pipes by means of steam blowing is achieved by the use of a receptacle into which steam is blown upon discharge from one end of a pipe; a linkage pivotally suspends an exchangeable mouthpiece adjacent to a front end opening of the receptacle and carries a stop member; actuation of the linkage places the mouthpiece over a front end of the pipe adjacent to said opening while removing said stop and, alternatively, places the mouthpiece over a front end of the pipe adjacent to said opening while removing said stop and, alternatively, pivots the mouthpiece to clear the pipe while causing the stop member to be placed in front of that front end.

Abstract: An improved speaker grille for incorporation in the housing of a light/siren assembly of a type which is mounted across the roof of a police car or other emergency vehicle, the improved grille being designed to significantly reduce the drag coefficient of the light/siren assembly due to the unique location of the grille openings.

Abstract: Apparatus for suppression of water flow noises in connection with a keel nted sonar dome. A solution of water soluble polymer is ejected through a series of holes along the leading edge of the sonar dome under forward movement of the ship. The concentration and flow rate is chosen to "bathe" the dome in a very dilute dispersion (of the order of 10 parts per million by weight) of the polymer.

Abstract: A slamming-resistant sonar dome canoe is provided herein. The canoe generally consists of a shell, e.g., of fiberglass-reinforced plastic e.g., polyester resin with an extensive internal reinforcement of plastic foam, e.g., epoxy foam in the bottom of the canoe, buttressed by an additional but simple lightweight metal framework e.g., steel or aluminum at the mounting flanges and in the upper portion of the canoe interior and preferably bonded thereto by the thermosetting polyester resin. This sonar dome canoe achieves the conflicting requirements for light weight and robustness in a canoe used in a slamming environment.

Abstract: A housing for an acoustic transducer includes means for dispersing internal reflections within the housing to minimize the incidence of such internally reflected acoustic pulses on the transducer itself, thereby avoiding the generation of spurious electrical signals for transmission to the translating circuitry.

Abstract: A portable receiver includes a housing which operates as an acoustical amplifier to increase the output level of the audio signals produced by a sound transducer. The sound transducer is located within a cavity in the housing and emits audio signals into the interior of the housing. The housing has vents located in its walls to permit the audio signals produced by the sound transducer to pass freely to the exterior of the housing. The vents are dimensioned such that the resonant frequency of the housing lies approximately at the center of the frequency range of the signals produced by the sound transducer. Matching the resonant frequency of the housing to the output signals of the transducer causes the housing to operate as a tuned resonator which amplifies the output signals of the transducer.