Abstract: An electronic memory stores votes cast for candidates by means of voting switches which are actuated by the voter. Shields mounted on hinges can be positioned over the switches. The shields have cut-out portions thereon which expose the switches. The voter can select from one group of candidates when a shield is positioned over the switches and from another group of candidates when the shield is not positioned over the switches. Switch means operated by movement of a shield on its hinge connects the switches to one portion of the memory when the shield is positioned over the switch and to a different portion of the memory when it is not so that the same switches can be used to vote for two or more different groups of candidates. A personal choice keyboard is provided. The keys actuate switches which are connected to the electronic memory for storing therein alphabetic representations of personal choice candidates selected by each voter.

Abstract: An acoustical horn suitable for use in conjunction with an acoustical driver to form a loudspeaker has a first section between its throat and a predetermined point therealong which has a first exponential flare rate, and a second section between the predetermined point and the mouth which has a second flare rate. The flare rates are chosen to afford improved frequency response over a single section exponential horn with the same length, mouth area and throat area.

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: A noise barrier wall having a transition area in the region of at least one unbounded edge and which employs controlled diffraction of sound to enhance the sound reducing properties thereacross. The transition area of the noise barrier is provided with either a row of absorptive shaped splitter panels, or a row of pickets, or other means of controlled transparency which provide acoustical shadowing equal to or greater than that of a solid wall for the frequency regions of interest.

Abstract: Method and apparatus for reducing jet noise in a turbofan engine by causing internal mixing of fan and primary air to reduce the maximum velocity of gases at the nozzle exit plane by creating a particular type of vortex flow at a distance of at least one nozzle diameter forward of the nozzle exit plane. In one preferred embodiment for a JT8D engine an array of eight roll-top vortex generators are provided on each side of the splitter wall between fan and primary flows, and a portion of the fan air may be introduced into the central portion or core of the hot primary air.

Abstract: A centrifugal fan is treated acoustically by the provision of tuned noise absorption cavities preferably including absorbent infill between an acoustically permeable scroll and casing of the fan. Alternatively, or in addition an acoustically absorbent panel structure is provided in spaced confronting relationship with the inlet port of the fan. The panel structure has an acoustically permeable facing spaced from a rigid backing and the space may be divided into noise absorption cavities and specifically Helmholtz type absorption cavities, the absorption bands of which are broadened by including acoustic infill. It is most advantageous to provide a multiplicity of Helmholtz absorption cavities tuned to respective different center frequencies of their acoustic absorption bands.

Abstract: A dual loudspeaker is set up to handle separately high frequency and low frequency sounds in the same piece of equipment. The apparatus comprises a single housing having a vertical partition dividing the housing into two chambers. A high-frequency driver in one chamber feeds into a relatively short horn path to a high frequency bell. A low-frequency driver in the other chamber feeds into a relatively longer horn path to a low-frequency bell. The high-frequency and low-frequency bells are located side by side on opposite sides of a partition and feed into a progressively expanding horn which serves simultaneously the output of both drivers.

Abstract: A speaker cabinet includes a baffle plate having at least one aperture for mounting a speaker unit, the baffle plate having a plurality of small areas over its entire surface and so constructed and arranged that the sound waves propagated along the surface of the baffle plate are scattered.

Abstract: A loudspeaker enclosure is disclosed which includes a horizontal bottom wall, parallel spaced vertical front and rear walls connected with the bottom wall, the front wall containing an opening for receiving a loudspeaker, and a horizontal top wall connected with the upper edges of the front and rear walls. The invention is characterized by the provision of vertical baffle walls which define a converging compression chamber behind the loudspeaker opening in the front wall, and a pair of exponential folded horns arranged laterally on opposite sides of the compression chamber. Each of the baffle walls between the compression chamber and the folded horns contains at least one opening adjacent its forward edge, each of the openings having a generally trapezoidal vertical cross-section, the vertical dimension of the front portion of the opening being greater than the vertical dimension of the rear portion of the opening.

Abstract: An exhaust silencer comprising a primary exhaust gas expansion chamber, a secondary exhaust gas expansion chamber having a greater volume than said primary expansion chamber, an acoustically tuned length of exhaust pipe leading from the primary expansion chamber to the secondary expansion chamber and representing the only outlet from said primary expansion chamber and the only inlet to the secondary expansion chamber, an outlet pipe leading from the secondary chamber and surrounding said exhaust pipe with clearance between said pipes, and a further pipe surrounding said outlet pipe with clearance between said pipes, the outlet pipe and the said further pipe being perforated along at least part of their lengths.

Abstract: In a setting device for presettable counters, a number of indicating rollers are arranged with symbols on their circumferential peripheral surfaces. Connected to each indicating roller is a ratchet wheel and an adjusting wheel. A switching device for each roller permits it to be moved in a step-by-step manner and otherwise to be locked in position. The switching device includes a switching pawl for engaging the ratchet wheel and moving the roller, a fixing lever for locking the adjusting wheel and roller in position, a control pawl and a key for displacing the control pawl. The control pawl is spring-biased against the actuating movement of the key. The control pawl displaces the switching pawl and the fixing lever in response to its displacement by the key.

Abstract: An exponential horn for use in a speaker is provided and includes a horn having a mouth, a throat and horn wall sections connecting the horn mouth and the horn throat. The horn wall sections define a horn whose cross sectional area progressively increases at a selected rate from a value S.sub.o at the horn throat substantially in accordance with the function S(z)=S.sub.o e.sup.mz. S(z) is the cross sectional area measured at any distance z from the horn throat, m is the flare constant defined as 4.pi.f.sub.c /c, where f.sub.c is the cutoff frequency of the horn and is from about 300 Hz to about 500 Hz. The horn mouth is rectangular in shape and has a perimeter substantially equal to one wavelength of the cutoff frequency of the horn. The distance between the horn throat and the horn mouth is from about 10 inches to about 17 inches.

Abstract: A pneumatic ear cushion for a headphone or ear defender is formed from two sheets of vinyl plastic. One sheet is molded to form concentric inner and outer walls about a central opening and a connecting sealing wall which is shaped to form a cavity that receives the user's ear. The second sheet of vinyl plastic forms a back wall to which an adhesive is attached for mounting the cushion to a headphone cup.

Abstract: A loudspeaker enclosure comprises a shell having an opening therein and a loudspeaker mounting baffle disposed over the opening. The shell is formed entirely from one or more diaphragm members or passive radiators which oscillate in response to selected low frequency sound waves emanating from a loudspeaker mounted within the enclosure. The diaphragms forming the shell reinforce the forward acoustic radiation from the loudspeaker and militate against the formation of standing waves within the enclosure.

Abstract: The disclosure concerns itself with labyrinth speakers systems which are provided with a plurality of internal partitions which are generally spaced from each other and are provided with apertures therein to form at least one tortuous path for a backwave generated by a loudspeaker. In one embodiment, the partitions are substantially cylindrical walls concentrically aligned with each other. The cylindrical walls have different diameters to form annular intermediate chambers. Other embodiments described include partitions which are planar and are substantially rectangular in shape. These partitions are spaced from each other along an axis of symmetry and are alternately provided with peripheral and central openings so that the backwave, while propagating between an initial and a final chamber of the enclosure, are successively broken up into a substantially annular shape and subsequently reconstituted.

Abstract: A speaker system in which at least one driver is mounted on an enclosure and is adapted to radiate sound waves outwardly from said enclosure in response to an input signal. A sound absorbing material is disposed on at least a portion of the outer surface area of said enclosure to reduce the effect of diffractions and reflections of said sound waves relative to said enclosure.

Abstract: A mechanically operable acoustic filter for varying the acoustic spectrum of transmitted sound signals. Sound signals, e.g. from a patient's skin when the filter is incorporated into the chest piece of a stethoscope, are received at an inlet orifice which may or may not be provided with an outer diaphragm. A thin, preferably Mylar filtering diaphragm partitions the interior of the chest piece into two chambers communicating with respective inlet and outlet orifices and each other through a central opening in the filtering diaphragm in line with a central passageway in a tensioning member for the filtering diaphragm. The position of the tensioning member is adjustable by a knob disposed outside the chest piece between a first position in which all frequencies pass by way of the central opening and successive positions in which the diaphragm is correspondingly tensioned at the same time the free vibrating area thereof is reduced.

Abstract: A device for eliminating the need for a guitar player to utilize his index finger for fretting guitar strings at different frets. A preferred embodiment comprises a metallic frame having three sections extending equiangularly from a central, common edge. A second element may comprise a barr which may be placed in contact with the strings on a guitar and held tightly thereagainst by means of a tension-exerting member which releasably grips the ends of the barr and is passed across one section of the frame. The frame may comprise a single metallic element constructed in one or more various shapes. Preferably, both the frame and the barr are at least partially covered with a low friction, relatively soft material, such as Teflon.

Abstract: A loudspeaker system is disclosed having a rigid framework which contains a high compliance loudspeaker connected to an adjustable air column tube. The adjustable air column tube provides exact 1/4 wavelength tuning for the speaker system, to further improve its low frequency response, in accordance with tuned enclosure theory.

Abstract: A toy cash register for displaying sales amount indicia including a plurality of corresponding indicia legs, which when manipulated cause a sales amount indicia display to be shown at the top of the register. The actuation mechanism for translating the above manipulation into a display includes a lower leg portion for each leg which defines a pawl mateable with a corresponding rotatable holding cam, each holding cam defining a cam opening for mating with the pawl. A spring biases the holding cam in a clockwise rotational direction and each such cam controls motion of a display indicia arm connected to a sales amount indicia display.