Abstract: Directivity of a sound source is significantly increased when the source is positioned within the geometrical center of a ring having a diameter and height of 1 wavelength and 1/2 wavelength respectively. Sound energy radiates to the ring and is re-radiated or diffracted at the top and bottom thereof. The re-radiated or diffracted sound energy thus appears to be generated by two simple sources, in phase and vertically arranged, one source being at the top of the ring and the other at its bottom, resulting in increased intensity along the horizontal plane bisecting the sources. The two phased sources at the top and bottom of the ring may be considered to be located along any imaginary vertical plane through the single source. Sound intensity in a desired plane or direction is thus increased without a concomitant increase in power, number of sources or components.

Abstract: A damper for tunably damping acoustic waves in an ultrasonic waveguide is provided which may be used in a hostile environment such as a nuclear reactor. The area of the waveguide, which may be a selected size metal rod in which acoustic waves are to be damped, is wrapped, or surrounded, by a mass of stainless steel wool. The wool wrapped portion is then sandwiched between tuning plates, which may also be stainless steel, by means of clamping screws which may be adjusted to change the clamping force of the sandwiched assembly along the waveguide section. The plates are preformed along their length in a sinusoidally bent pattern with a period approximately equal to the acoustic wavelength which is to be damped. The bent pattern of the opposing plates are in phase along their length relative to their sinusoidal patterns so that as the clamping screws are tightened a bending stress is applied to the waveguide at 180.degree.

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 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: A microphone unit particularly suitable for conference applications is provided, wherein an acousto-electric transducer is disposed between two dish-like back-to-back sound collectors, each having a central aperture exposing one side of the transducer, which preferably has a single planar diaphragm.

Abstract: A commutator has a plurality of spaced, electrically conducting segments, each of which has a physical dimension determining the relative time duration of brush contact with said segment during commutator rotation with audible brush noise being generated between the brush and said consecutive segments, the noise including a fundamental frequency component at a frequency related to the frequency at which the consecutive segments pass the brush. The physical dimension of the consecutive segments varies from each segment to the next according to a predetermined pattern effective to vary the relative time of brush contact from each segment to the next during rotation and thus reduce the amplitude of the fundamental frequency components to make the brush noise less tonal in character and thus less annoying.

Abstract: A bi-directional speaker unit is provided by a wedge shaped member having intersecting walls with spaced parallel angled louvers.The unit is coupled to a base member through a snap on means permitting other type units to be used with the same base member.

Abstract: An enclosure for transducers incorporates an interior acoustically reflective shell. This acoustically reflective shell is shaped so that the inner surface thereof is the envelope of at least a section of a cylinder of elliptical cross section, an ellipsoid of revolution, or the envelope of a multitude of said shapes oriented so that the elliptical shapes share one common focus and each has one distinct focus. In this last case, transducers are placed at the distinct foci so that sound produced by them is directed substantially toward that portion of the elliptical acoustically reflective shell to which the distinct foci belong. In operation sound generated by the transducers, operating in phase with one another, is focused and concentrated at the common focus such that this common focus acts as a singular source of phase coherent sound of any desired angular beamwidth and intensity.

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: A sonic waveguide arrangement for use in transmitting sonic energy from one point to another along a non-linear path is disclosed herein and utilizes at least two different waveguides. One which is linear or straight in configuration and one which is curved. The first of these two waveguides is of a type which can transmit sonic energy over a relatively long linear or straight line path with relatively low transmission losses and the second is of the type which can transmit sonic energy over a relatively short curved path with relatively low transmission losses.

Abstract: A speaker grille bezel-retainer terminating in a tubular portion with multiple groups of radially intermittent serrations axially displaced to receive a matching bezel ring having an inside diameter with alternate tabs and cut-outs and the tab is shaped to form a ramp to axially advance the ring on the bezel while rotationally engaging spaced, aligned pairs of serrations.

Abstract: The present invention pertains to a method and apparatus for achieving a uniform omnidirectional radiation of sound waves, particularly at high frequencies, and for increasing selectivity and separation at frequencies in the medium to high frequency wave band The apparatus consists of a series of reflector-diffractor barriers which are frequency selective. Each barrier is operative to transmit sound waves of a frequency greater than a selected value and to reflect and omnidirectionally radiate sound waves of a frequency less than the value.

Abstract: A device capable of operating over a wide frequency band with a constant angular width of the radiation lobe of elastic waves. It comprises in combination at least one omnidirectional reversible electroacoustic transducer and an assembly of reflecting surfaces of zero acoustic impedance which define a space inside which said transducer is arranged.

Abstract: An acoustical transducer and grille combined into a single unit. The grille is acoustically transparent and includes a plurality of wave guides separated for through-passage of sound. Situated in the midst of the grille is a mounting for the acoustical transducer. The transducer mounting has a central opening and an annular groove formed about the periphery of the central opening into which the acoustical transducer is mounted. A second acoustical transducer, larger in dimension than the first acoustical transducer, may be employed as well, also mounted within the confines of the grille. For greatest acoustical clarity, the first and second acoustical transducers are coaxially oriented.

Abstract: A sound insulating arrangement for a vehicle including a gear shift lever extending upward into the passenger compartment of the vehicle through an aperture formed in the floor panel thereof is disclosed. The arrangement comprises a shift lever boot having a bottom opening larger than the aperture and a top opening in fitting engagement with the gear shift lever and secured to the floor panel so as to cover the aperture. The arrangement also comprises a sound insulating plate having a center hole for penetration of the gear shift lever and a number of slits radially extending from the center hole for freedom of movement of the gear shift lever. The shift lever boot is provided at least partially with a bellows portion in one fold of which the sound insulating plate is fitted.

Abstract: For use with a cabinet containing at least one loudspeaker, a grille is provided which is comprised of elongated frame members connected by corner brackets. A rigid superstructure, comprising corner ridge members and one or more central ridge members joined by ridge joint members, is attached to the frame at the corner brackets, and a covering material is disposed over the superstructure and frame. Any size grille can be constructed using the same corner brackets and ridge joint members.

Abstract: A speaker system in which a speaker unit mounting frame and unit boards are mounted in juxtaposition on a baffle board, and at least a part of the unit board surface contiguous to the surface of the speaker unit mounting frame is bevelled to form a gently-sloping face.

Abstract: A multipoint reflective target system for use as sonar targets. The system ncludes a plurality of small spaced apart reflectors that are interconnected by an elongated flexible tether. The tethered reflectors are then towed in the ocean and form an elongated multipoint reflective target comprising a string of spaced apart reflectors moving under and about parallel to the ocean surface. This target is sonified by a sonar pulse and generates a reflected signal having a predetermined shape. The shape of the reflected signal is determined by a selection of parameters such as the length of sonar pulse, the spacing of the reflectors and the size and material of the reflectors. By properly selecting these parameters it is possible for the multipoint reflective target system to resemble much larger actual or similated targets.

Abstract: A loudspeaker having a totally integrated acoustic system which reduces unwanted cabinet diffraction of the sound waves to minimum; resulting in maximum sound wave dispersion with directional accuracy.

Abstract: An underwater acoustic reflector and method for making an acoustic underwater reflector is described herein whereby electrodes are immersed in an aqueous electrolyte solution and thereafter connected to a supply of electrical current. The electrodes are selected such that bubbles form on at least one of the electrodes, providing a layer of acoustic reflective bubbles. Control of the reflectivity properties according to the intensity of the electrolyzing current is also described.

Abstract: The speaker grill is a part of a molded plastic member which may form a wall of housing for a device which includes an audio transducer. The plastic member includes provisions for supporting the audio transducer adjacent the grill, which has openings for the transmission of sound. The grill has stress regions in which there are no openings, which are in tension when the grill is flexed to thereby increase the strength of the grill. The stress regions may extend across the grill in an "X" pattern, or in any other pattern wherein one of a plurality of such regions extends transversely with respect to another region. The openings for sound transmission may be slots extending from the sides of grooves, which form labyrinth openings so that there is no direct passage through the grill, thereby tending to prevent entry of undesired objects.

Abstract: An electroacoustic transducer assembly adapted to filter sound waves in a digital communication system incorporates a plurality of tandemly arranged tubular members and a transducer. Each tubular member includes an apertured plate end, a tubular cavity and an open end. The open end of each tubular member is secured to the plate end of the adjacent tubular member to form a housing with a divided longitudinal passageway. The open end of the housing is secured to the transducer. Every tubular cavity is partitioned into longitudinal sections by structural elements to inhibit cross mode resonance. The apertures, cavity lengths and structural elements are dimensioned relative to the cavity cross sections to suppress passage of sound waves outside a predetermined frequency band.

Abstract: A speaker cabinet comprises an enclosure having a top, bottom, front, back and two side panels, each panel being contiguous with an adjacent panel along its four edges, and the front panel having a sound port and interiorally of which is mounted a speaker, an improvement comprising a sound post extending and wedged between the front and back panels, an elongated bass bar secured along its length to the front panel, a pair of elongated blocks, each extending between and contacting the front and back panels, one of the blocks being secured to the top panel along its length and the other block secured to the bottom panel along its length, and a support plate secured along the back panel and extending between the side panels.

Abstract: Intensity of vibrations emitted by tool and workpiece acted upon is reduced by an enveloping mat of floppy fibres. In a heel attacher, for instance, the mat reduces by 14 or more decibels, and an operator incurs no risk of injury to his hands should they be in the path of the mat when it is moved to or from a heel and shoe being attached.

Abstract: Disclosed is a random phase diffuser which is inserted between a transducer and an insonification subject in accoustical imaging. The diffuser is comprised of an array of lossless elements which cause sound emitted by the transducer to be passed through and emitted with a phase value of 0.degree. or 180.degree.. Additionally disclosed is the combination of a random phase diffuser with a wedge coupling feature for increasing insonification efficiency.

Abstract: A corner reflector lined with resonant frequency determining hollow gas-filled spheres is interrogated with a plurality of frequencies, including the resonant frequency and the acoustic return is substantially only the resonant frequency. A four-quadrant device is provided and each quadrant of the device is lined with different sized spheres for four different resonant frequencies, and installed according to predetermined geographical coordinates and orientation. With the combination of resonant frequencies, the interrogating vessel can obtain directional as well as identifying information with respect to the device.

Abstract: An energy curtain is formed by exciting high order beam modes in an open resonant cavity. Depending on mode number, the energy resonates in a mathematically determined pattern. A detector senses changes in the resonant condition caused by the presence of an object in the pattern. The apparatus may be used in a variety of applications, including the protection of a machine operator from a hazardous area of a machine, parts counting, and intrusion detection.

Abstract: A grill for a loudspeaker has a relatively thick metallic plate with a loudspeaker opening and a plurality of T-shaped bars across the opening, and a relatively thin metallic plate with a loudspeaker opening and a plurality of U-shaped bars across the opening. The plates are mounted together so that the U-shaped bars are located between but spaced from the T-shaped bars to provide physical protection to and good acoustic qualities for the loudspeaker. The relatively thick metallic plate provides a good heat sink for electronic equipment.

Abstract: Resonant acoustic beams modes are generated by an acoustic energy source and a plurality of reflectors disposed along a path.