Abstract: A lens incorporates two reflective shells. One shell's surface is generated when a parabola is rotated around a line which lies in the parabolic plane perpendicular to its axis of symmetry. The other shell's surface is generated when an ellipse is rotated about a line lying in the elliptic plane and passing through one focal point at a finite angle to its major axis. The parabolically-generated shell has a characteristic focal curve while the elliptically-generated shell has both a characteristic focal curve and a focal point. The lens incorporates these shells which are aligned so that they have coincident focal curves and axes of rotation. Plane wave radiation travelling parallel to the axis of rotation of the lens will be focused at the focal point of the elliptically-generated shell. Conversely, a transducer placed about this common focal point and can produce radiation which will be converted into a plane wave radiation.

Abstract: A combination skid resistant and vibration dampening device formed from rubber-like material having a high coefficient of friction which is integrally bonded to cellular foam type material which has high impact absorption capacity.

Abstract: Disclosed is an automobile muffler having a drain pipe communicating with the upperstream, upper half inside sound-deadening area of its outer pipe, thereby allowing the moisture of the air drawn into the sound-deadening space to leave for the surrounding atomosphere via the drain pipe prior to condensation of the moisture to water in the sound-deadening space, thus making it unnecessary to drain water from the muffler.

Abstract: A sound absorbing structure is formed of adjacent panels which provide narrow slots opening into first resonance cavities formed behind the panels. Support strips provide secondary cavities between adjacent first cavities to reduce acoustical coupling between adjacent first cavities. The resulting sound absorbing structure provides substantial sound absorption at frequencies of less than about 1,000 Hz.

Abstract: A disk on a wheel-tpe odometer assembly is provided with a integral spring pawl that operates with the normally provided transfer teeth on the highest number wheel to effect a positive detent that prevents this last wheel from backward droop.

Abstract: An acoustical impedance inducing device is created for axial insertion into the longitudinal air column of a wind musical instrument. The device includes a first annular band of first predetermined thickness and a second annular band of approximately twice the thickness of the first band. A first web interconnects the first and second bands and maintains the bands at a predetermined axial spacing. The web is formed of strips diagonally disposed between the first and second bands and defining a triangle shaped aperture between adjacent bands, with the base of the triangle being colinear with an edge of one of the first and second bands. A third annular band, twice the thickness of the second, may be separated from the second band by a second web; or the device may be placed in a tubular portion of the instrument at a location where an end of the tubular portion is spaced from the second band by the axial width of the web.

Abstract: A rotary shaft is provided with at least two pins at its one end, these two pins fitting into two holes of the cover. The other end of the rotary shaft carries a polygonal screw pin for screwing on the adaptor.

Abstract: A noise reducing apparatus in the form of a hollow body comprising two or more passage groups consisting of a plurality of passages. The length of each passage is determined such that the sound waves emitted from the passages of the adjacent passage groups form plane waves which are shifted by a half wavelength so that plane waves interfere each other. The apparatus can be secured to an opening of construction and reduce the level of sound pressure from a sound source without any closed shield construction surrounding the sound source.

Abstract: A stamp formed muffler comprising a pair of internal plates and a pair of external shells is provided. The internal plates are stamp formed to define first and second spaced apart arrays of tubes and a single intermediate tube therebetween. Tubes in one array may have perforations or apertures to permit expansion of exhaust gases, while the other array may define at least one tuning tube. The tubes are disposed on the internal plates such that at at least one location thereon a straight line extending entirely across said internal plates will intersect only the one intermediate tube. The external shells are stamp formed to define a plurality of chambers which cooperate with the tubes in the internal plates. The chambers are separated from one another by a crease disposed to align with the intermediate tube. The crease is characterized by a single outwardly convex portion to engage the single bulb. As a result, the crease is not provided with recesses that conceivably could retain corrosive materials.

Abstract: A wide dispersion baffle for a vertically oriented loudspeaker includes a first semi-conical reflective section that is concave toward the speaker and has a semicircular rim positioned at the periphery of the speaker. It extends at an angle of about 45.degree. to the radiation axis of the speaker to its apex on the speaker axis. A second semi-conical reflective section is convex toward the speaker and extends from the apex of the first semiconical section at substantially the same 45.degree. angle with respect to the speaker radiation axis. Sound emanating from the vertically directed speaker is reflected by both the concave and convex semi-conical reflector sections in a pattern centered about a substantially horizontal plane, but the sound is reflected through widely diverging angles in such horizontal plane. Baffle arrangements can provide horizonal dispersion patterns of any angular width between about 180.degree. and 360.degree..

Abstract: An enclosure for a transduction element incorporates a geometrically shaped acoustically reflective shell. This acoustically reflective shell is shaped so that the inner surface thereof is at a least a section of that shape generated when a parabolic structure is rotated around a line which, lies in the plane of the parabolic structure, is perpendicular to the major axis of the parabolic structure. Such geomtrically generated shapes will have one distinct focal curve. A transduction element placed about this focal curve will, in operation, cause acoustic radiation to be produced which will be characterized by a plane wavefront of coherent radiation. Said device may alternately act as a transducer which produces a 360 degree beam width by placement of a plane wavefront producing transduction means at a position above the acoustically reflective shell and parallel to the plane of the distinct focal curve.

Abstract: The invention comprises a microphone and loud speaker system in which the components include a cylinder having a center section and an end section at each end of the center section in axial alignment with one another. The adjacent ends of the center and end sections are elliptical and lie in planes oriented at an angle of 35.degree.16' to the longitudinal axis of the module, the long axes of the ellipses are oriented at 45.degree. to horizontal. The planes of the elliptical ends are substantially isomorphic to the tympanic membrane of the human hearing structure and represent half the dihedral angle of a regular tetrahedron. All of the loudspeaker transducers are shielded by sheilding cylinders with elliptical end faces lying in planes oriented, at half the dihedral angle of a regular tetrahedron, namely, 35.degree.16' to the axes of the cylinders, with the long axes of the ellipses oriented at 45.degree. to the horizontal.

Abstract: A noise silencer for highway is adapted to be stuffed in a joint gap formed in a highway. It has a rectangular casing and padding enclosed in the casing. The casing is provided with a vent hole adapted to be closed by a plug. Before mounting the noise silencer, air is firstly sucked out from the silencer through the vent hole to flatten the padding and the vent hole is plugged. After the silencer has been mounted, the vent hole is open to inflate the padding so that the silencer will be pressed against the opposite walls of the joint gap.

Abstract: An anchoring element for a device for use in the ear canal of a wearer includes a body defining a cavity for transmission of external sound through the ear canal to the wearer and having a first portion sized and constructed to fit easily within the ear canal, an inflatable bladder removably disposed about the body and adapted for inflation by air delivered into a chamber defined by the body, to cause the bladder to inflate to resiliently engage and conform to irregularities and changes of shape of the surrounding wall of the ear canal of the wearer, e.g., during chewing. The bladder inflates in a manner to seal uniformly with the ear canal wall about the device, to hold the device firmly and securely in position in the ear canal. Pressure relief means associated with the bladder provide for venting excess air of inflation from the chamber.

Abstract: Disclosed is a diving computer in the form of a circular slide rule for aiding a SCUBA diver in planning one or more dives within a short amount of time, including more than one depth per dive, so that the diver may avoid risking decompression sickness. The computer has two faces, one of which calculates the increase of pressure within body tissues during a dive and the other of which calculates the decrease of this pressure after surfacing. The result of one side's calculation is used as the initial value for the other side's calculation, permitting the diver to track net residual pressure over a series of rapid repeated and/or multiple-level dives, and by so doing, avoid excessive tissue pressures that might cause decompression sickness.

Abstract: A human sound muffler and indicator for placement around the mouth of a user to absorb most of the sound emanating from the user's mouth including a microphone and associated electrical circuit for receiving unabsorbed sound and providing an indication of the intensity of the unabsorbed sound.

Abstract: A muffler for use with an internal combustion engine or the like having improved attenuation capabilities together with lower back pressure. The muffler has an elongated outer casing and an inner casing, the tubular ends of which extend beyond the outer casing for inlet, and outlet conducts. The central portion of the inner casing forms a continuation between the ends and has a differently configured but substantially equal cross-sectional area as the ends. The outer casing forms a sealed relationship with the inner casing adjacent the ends thereof. The central body portion is configured to have a portion in contact with the outer casing and a portion spaced from the outer casing. The surface of the spaced portion is perforated and sound absorption material is positioned in the space between the inner and out casing.

Abstract: An acoustic tile that provides soundproofing in a modular wall, such as is used in a modular panel office system, comprises a rigid rectangular metallic frame, a septum formed of a calcium carbonate-filled molded synthetic rubber polymer, a layer of low-density fiberglass and a layer of high-density fiberglass. The front of the frame is covered by fabric, and the back of the frame has fittings to attach the acoustic tile to a wall panel.

Abstract: A sound-permeable loudspeaker cover including a frame in which are arranged mutually crossing webs of a synthetic plastic material delimiting sound passage openings. A sound-permeable material, for instance a fleece, a textile fabric or a knitting, covers the sound passage openings, and is arranged approximately in the middle of the webs. The webs are produced as a single part according to the injection molding process, and penetrate the sound-permeable material to anchor it at a plurality of individual locations.

Abstract: A percussion instrument includes a drum body and a percussion head movable with respect to and stretched over the drum body. A master tensioning member is provided for pulling the drumhead downward to enable a musician to vary the pitch of the sound produced when the drumhead is struck. The master tensioning member is operatively coupled to the drumhead, and is adaptable for use with drumheads of varying size. A lever system is provided for moving the master tensioning member vertically downwardly. A foot pedal is provided for enabling the user to actuate the lever system. The pedal includes an engaging tooth, and is swivelable to engage and disengage the tooth with complementary teeth to lock the pedal selectively in position. The pedal tooth thereby permits the user to adjust and fix the tension on the drumhead. The pedal is connected to the lever system by a movable fulcrum, which permits the user to exert a smooth, even force when depressing the pedal and actuating the lever system.