US3845838A - Acoustic distributor - Google Patents

Abstract

An acoustic distributor in which a cylindrical enclosure, constructed to provide extreme attenuation of sound passing through the walls thereof, contains a radio-type loudspeaker. The enclosure has a plurality of peripherally located and spaced acoustic ports to which individual acoustic headsets may be coupled to that sound generated within the enclosure is propagated by way of the listening tubes of the acoustic headsets to several listeners. Each of the headsets may be individually connected and disconnected from the distributor without interfering with the sound transmission to other headsets and each acoustic port is provided with a slide valve mechanism mounted exteriorly of the soundproof enclosure and arranged to be easily and substantially automatically opened as a consequence of the motion employed in coupling a listening tube to the associated acoustic port.

Description

United States Patent [1 1 Malmrose et al.

[451 Nov. 5, 1974 ACOUSTIC DISTRIBUTOR [75] Inventors: Gerald E. Malmrose, Chatsworth; Ulf R. Helgesson, Woodland Hills, both of Calif.

[73] Assignee: Acoustifone Corporation,

Chatsworth, Calif.

22 Filed: June 25, 1973 21 Appl. No.: 372,798

[56] References Cited UNITED STATES PATENTS 3,353,625 11/1967 Scanlon ..181/31B Primary Examiner-Stephen .l. Tomsky Attorney, Agent, or Firm-Benjamin Dewitt [57] ABSTRACT An acoustic distributor in which a cylindrical enclosure, constructed to provide extreme attenuation of sound passing through the walls thereof, contains a radio-type loudspeaker. The enclosure has a plurality of peripherally located and spaced acoustic ports to which individual acoustic headsets may be coupled to that sound generated within the enclosure is propagated by way of the listening tubes of the acoustic headsets to several listeners. Each of the headsets may be individually connected and disconnected from the distributor without interfering with the sound transmission to other headsets and each acoustic port is provided with a slide valve mechanism mounted exteriorly of the soundproof enclosure and arranged to be easily and substantially automatically opened as a consequence of the motion employed in coupling a listening tube to the associated acoustic port.

10 Claims, 10 Drawing Figures nuv 5:914 3.8458 8 PATENTED sum 10F 3 3 Background of the Invention This invention relates to sound distribution apparatus and more particularly to a' reliable, rugged and economically manufacturable acoustic distributor of the type used for distributing sound froma single electroaccoustic transducer to a plurality of listeners without disturbing other nearby persons.

One problem encounted in the development of practical acoustic distributors for classroom use has been the difficulty of achieving an adequate sound level at the ears of all listeners while at the same time keeping sound leakage at a low enough level to preclude disturbance of nearby persons engaged in other activities. In the prior art one approach has been to provide each listener or student with a headset which includes a pair of electrically energized transducers. Such systems are disadvantageous for use in primary school classrooms in that the relatively fragile electric headsets must be entrusted to small children. Additionally, while such electric headsets do not actually carry dangerous voltages it has been found that educational system administrators are generally quite reluctant to permit unsupervised use of electrically wired headsets in primary school classrooms An additional factor which militates against the use of such prior art systems is the relatively high cost of maintenance associated with providing individual electric headsets to a large group of listeners.

In the recent development of audio-visual equipment for use in classrooms, libraries, hospitals, etc., the trendhas been away from the use of electrical headsets to the use of acoustic distributors and acoustic headsets which include an elongated hollow listening tube having a rigid probe at its input end which can be coupled Summary of the Invention In accordance with a preferred form of the present invention, the foregoing objects are achieved by an arrangement in which each listener is provided with an acoustic headset which includes a listening tube having at its sound input end a rigid probe for coupling to one of the acoustic ports of an acoustic distributing unit. The acoustic distributor is a thick-walled enclosure, preferably cylindrically in form constructed to provide extreme attenuation of sound passing through the walls thereof and having a radio-type speaker supported therein. Around the periphery of the enclosure are spaced a plurality of sound output ports through which sound waves generated within the enclosure are propagated to the individual acoustic headsets. Each acoustic port has associated therewith a slide-valve mechanism mounted exteriorly of the soundproof enclosure and operable from a closed position to an open position when the rigid probe of a headset is inserted into the associated port. The slide-valve mechanism tends to hold the headset probe in place in the acoustic port by applying force perpendicular to the probe so that inadto one of a plurality of acoustic ports in the distributor.

In these acoustic distribution systems, it is important that sound be delivered to the several listeners at substantially equal intensities while limiting the leakage of sound energy to avoid interference with the activities of nearby non-listeners and thereby permit several groups of students to be engaged in different activites in a single room. To invite and encouragethe use of such apparatus by primary school children, it is most important that the acoustic distributor be arranged for easy and unattended use by small children.

Accordingly, it is a primary object of this invention to provide an improved apparatus for distributing sound to a plurality of listeners while maintainingthe sound level to which non-listeners in the immediate area are subjected at a relatively very low level.

It is a further object of the present invention to provide areliable, rugged and economically manufactur able acoustic distributor having a plurality of acoustic ports for connection of acoustic headsets and having an acoustic valve mechanism. positioned adjacent each port outside the soundproof enclosure and arranged for I facile and substantially unattended usage by children in the 3 to 10 year age group.

It is an additional object to provide an acoustic distributor having slide valve mechanisms which operate to automatically grip and hold the headset probe in the inserted position so that inadvertent disconnection of the headset from the distributor is substantially avoided.

vertent dislodgment is avoided. Further, each slidevalve automatically closes upon intentional removal of the probe so that sound leakage from the enclosure by way of acoustic ports which are not in use is substantially avoided.

Brief Description of the Drawings FIG. 1 is an exploded side view illustrating the major parts of an improved acoustic distributor in accordance with the invention; I

FIG. 2 illustrates a cross-section of the speaker supporting. gasket;

FIG. 3 is a top view of the manifold component of the assembly shown in FIG. 1;

FIG. 4 illustrates a cross-section of the manifold taken along the lines 4-4 of FIG. 3;

FIG. 5 is a bottom view of the manifold component;

FIG. 6 is a bottom end view of the top component of Description of the Preferred Embodiment The foregoing and other features of the present invention will be better understood by consideration of the following detailed description of one specific acoustic distributor constructed in accordance with the invention. As shown in FIG. 1 the acoustic distributor assembly includes a thick-walled top member 13, a radio-type lounspeaker 20, an acoustic manifold 32, and a base member 27 all of which are generally cylindrical in form. For clarity, the valve mechanisms associated with each acoustic port 34 of the manifold have been omitted from FIG. 1 but are shown in detail in FIG. 8

and will be described more particularly in the discussion of the structure shown in FIG. 8.

The major components 13, 20, 27 and 32 as shown in FIG. 1 are assembled together by moving the manifold 32 downwardly until it nests within the base member 27, and by securing the speaker 20 including its peripheral sealing ring or gasket 21 between the upper surface of the manifold 20 and the lower surface 18 of the top member 13. The generally cylindrical top member 13 has a plurality of peripherally spaced flutes or grooves 17 which cooperate with the slide-wave mechanisms (in a manner to be described hereinafter) to enhance the facility with which the distributor can be used. In cross-section, as shown in FIG. 7, the top member 13 has the form of a truncated cone with a slightly curved top surface 19, relatively very thick walls 61, and a fairly large internal cavity for accommodating the backside of the speaker 20. The speaker 20 conventionally includes an electrical signal input cord which extends outwardly through a hole in one side wall of the top member 13 and may be connected to a source of audio frequency signals such as a tape recorder/player. The sealing ring or gasket 21 which encompasses the periphery of the speaker has an internal groove 22 which snaps over the peripheral edge of the speaker. When the gasket 21 is clamped between the manifold 32 and the top member 13, it not only seals the enclosure to avoid sound leakage to the surrounding area but also minimizes sound conduction from the speaker rim to the side walls of the other components. That is, the sealing ring or gasket 21 seals the junction line between members 13 and 32 to avoid sound transmission therethrough, and also resiliently suspends the speaker 20 to avoid sound conduction directly from the rim of the speaker to the solid walls of the enclosure. To that end, the gasket 21 is preferably formed of a very soft and resilient vinyl polymer. The several components as described above are secured together by self-tapping screws which extend upwardly from the bottom surface 28 of the base member through appropriate holes 39 in the manifold (FIG. 4) to engage aligned apertures 65 in the top member.

As best shown in FIGS. 3, 4 and 5, the acoustic manifold 32 is a generally cylindrical structure having a central dome 40 which faces the front of the loudspeaker 20 and functions in cooperation with annular V-shaped groove 41 to provide a shaped acoustic chamber for directing high intensity sound waves from the speaker to all of the twelve acoustic ports 34. The acoustic ports 34 are equiangularly spaced around the periphery of p the manifold and extend horizontally outward from the annular groove 41 through the side walls 42. Each acoustic port 34 is centered within a vertically tapered surface 37 located between a pair of spaced ribs 36. As best shown in FIGS. 4 and 5, the outer surfaces of the ribs 36 are vertical while the surface 37 between each pair of ribs is tapered downwardly so that when the manifold is assembled within the base member 27, each pair of ribs forms, in conjunction with the cylindrical outer wall 29 of the base, a pyramidal space for containing one of the slide-valve mechanisms.

As shown in FIG. 8, the manifold 32 nests within the base member 27 with its bottom surface resting on the flat bottom 28 of the base member and with the outer surfaces of ribs 36 disposed in interfacing adjacency with the inside surface of the sidewalls 29. Aligned with each acoustic port 34 is a vertical slot 30 in the side wall 29 of the base member. Each slot 30 is further aligned with one of the vertical grooves 17 so that each groove 17 and the aligned slot 30 cooperate to provide a guideway for directing the rigid probe 26 of a headset 24 into the associated acoustic port 34.

Within the pyramidal cavity between adjacent ribs 36 there is contained a slide-valve mechanism comprised of a slider 71, a small diameter compression spring 80 and a spring supporting pin 82 which is formed as an integral part of the base member 27 and extends vertically upward into a re-entrant cavity 79 in the bottom of the slider 71. When viewed from the side as shown in FIG. 9, the slider 71 is substantially rectangular and has first and second planar outer surfaces 73 and 75 with the surfaces 73 and 75 being at an angle of about 7 so that an exterior shoulder is formed along the line 76. This shoulder 76 rests against the interior surface of the base member side wall 29 so that the slider 71 is free to pivot about an axis formed by the shoulder 76 whereby the inner planar surface 78 of the slider is free to pivotally adjust itselt to closely contact the tapered surface 37 above and below the port 34. By this arrangement the slider 71 although mounted exteriorly of the soundproof enclosure is held closely adjacent to and is capable of sealing the port 34 (when the particular port is not in use) so that sound leakage outwardly from the distributor is reduced to a level of the order of 60 decibels below the internal sound intensity level.

The several components of the acoustic distributor preferably are formed by molding from polymeric ma terials. More specifically, the base member 27 is preferably made of acrylonitrile-butadienestyrene; the top member 13 and the manifold 32 are formed of general purpose woodflour filled phenolic resin; and the sliders 71 are made from a medium-soft (70 shore) vinyl polymer.

It is to be emphasized that the structural arrangement of the slide-valve mechanisms is particularly advantageous in that the insertion and removal of headset probes 26 from the several acoustic ports 34 is very easy and uncomplicated so that even the smallest primary school children tend to be invited and encouraged to use the apparatus. The ease of usage is attributable, in part, to the arrangement in which the slidevalve mechanisms are mounted exteriorly of the soundproof enclosure to function in cooperation with the probe guideways formed by the grooves 17 and the slots 30. That is, a listening tube probe 26 may be connected to the distributor by simply pushing the end of the probe 26 downwardly along one of the grooves 17 whereby it engages the curved upper surface 77 of the slider 71, the slider 71 is moved down and the probe,

in substantially the same motion, enters the acoustic port 34. In FIG. 8, reference numberal 86 indicates one of the slide-valves in the downwardly pressed or open position. The slide valve arrangement provides the additional and important advantage that when the probe 26 is positioned within the acoustic port 34, the associated slider 71 maintains a modest pressure against the bottom surface of the probe so that the of distributors employing poppet-type spring loaded valves, which tend to expel the listening tube probe from the acoustic port, it has been found that inadvertent pulling on the listening tube, by a small child, frequently results in the probe being expelled from its port. This inadvertent disconnection tends to discourage small children from using the apparatus.

. In the economical manufacture of apparatus of the type described, it is most desirable that the manufacturing tolerances be substantial. The slide-valves 71 permit relaxed manufacturing tolerances in the sense that the probes 26 are not required to be precision manufactured for close-tolerance fit within the acoustic ports 34. A further advantage of using slide-valves rather than poppet-type valves is the fact they provide positive sound coupling. That is, with the slide-valve mechanisms a student cannot have his headset physically attached to the distributor without the slide-valve being fully opened. This enables the teacher to verify at a glance that the particular student is receiving sound at his headset. In contrast, with the use of poppet-type valves it is possible for a child to insert his headset probe loosely into an acoustic port without opening the associated valve and, in the absence of closesupervision, it may be some time before the teacher becomes aware that the particular headset is not receiving sound.

While the present invention has been shown and described in one exemplar form only, it will be obvious to those skilled in the art that it is not so limited but is susceptible to various changes and modifications without departing from the spirit and scope thereof.

We claim:

1. ln an acousticdistributor for use in classrooms and the like for transmitting sound waves from a single electro-acoustic transducer to a plurality of listeners without disturbing other nearby persons:

a substantially cylindrical thick-walled enclosure formed of sound absorbing polymeric material and having an interior-to-exterior attenuation characteristic for audio frequency acoustic waves of the order of about 60 decibels; loudspeaker mounted within said enclosureand adapted to be electrically connected to a source of audio frequency signals for producing high intensity acoustic waves within said enclosure;

a plurality of angularly spaced substantially cylindrical apertures extending radially outward through the walls of said enclosure in a single horizontal .plane spaced in front of said loudspeaker whereby sound waves of substantially equal intensity are propagated toward all said apertures;

a plurality of acoustic headsets, each including an elongated listening tube having at its input end a semi-rigid probe adapted to be inserted into any one of said apertures, for conducting sound waves from said one aperture to the person using the particular headset;

a plurality of valve mechanisms mounted exteriorly of said thick-walled enclosure, respectively adjacent the outer ends of different ones of said apertures;

with each valve mechanism being operable, in a direction substantially normal to the longitudinal axis of the adjacent aperture, from its closed position to its open position upon, and as a direct consequence of, the insertion of a listening tube probe into the associated aperture and being operative to exert a retaining force on the inserted probe whereby the probability of inadvertent disconnection of the headset listening tube from the enclosure is substantially reduced.

2. An acoustic distributor comprising:

a thick-walled enclosure substantially impervious .to

sound waves;

a speaker mounted within said enclosure and adapted to be coupled to a source of audio frequency electrical signals for producing high intensity sound waves within said enclosure;

a plurality of sound conducting ports extending through the walls of said enclosure from an interior sound chamber adjacent the front of said speaker to the exterior of said enclosure; and

slide-valve means mounted exteriorly of said enclosure adjacent each port and slidably operable, in a direction substantially normal to the axis of the adjacent port, from a closed position to an open position and vice-versa whereby sound leakage from said enclosure by way of ports not having listening tubes coupled thereto is substantially avoided.

3. An acoustic distributor in accordance with claim 2 in which:

said enclosure comprises a substantially cylindrical manifold portion with said sound-conducting ports extending radially through the side walls of said manifold portion and being angularly spaced therearound in a single horizontal plane.

4. The acoustic distributor of claim 2 wherein each slide valve means comprises (a) a slide valve element which is reciprocally movable in a direction substantially normal to the port with which it is associated, and (b) spring means for resiliently biasing said element toward the closed position and contiguously adjacent and covering the exterior end of the port associated therewith.

5. The acoustic distributor of claim 4 wherein each slide-valve element is formed of a relatively soft and resilient polymeric material and has a wedge-like configuration withthe thicker portion below the associated port so that when the wedge-like valve element is moved upwardly by' its associated biasing means, it wedges between the outer surface of the enclosure side wall and a peripherally encompassing base member to thereby substantially seal the associated port against undesired sound leakage.

6. The acoustic distributor of claim 4 wherein each of said ports is adapted to receive a hollow semi-rigid probe carried at one end of a headset listening tube and wherein each slide valve element is formed of a relatively soft and resilient polymeric material and has a wedge-shape configuration, with the slide valve element being contacted by said rigid probe and moved from the closed position to the open position upon insertion of the rigid probe into the associated port.

7. The acoustic distributor of claim 3 wherein said enclosure provides a sound intensity differential of the order of decibels between the interior and the exterior thereof and wherein said slide-valve means comprises a plurality of wedge-shaped slide valve elements angularly spaced around the exterior of said enclosure, respectively overlying the outer ends of said ports, and eavhmovable downwardly to accommodate insertion of a listening tube probe into its associated port.

8. An acoustic distributor in accordance with claim '4 and further including a plurality of sound tube headsets for respectively conducting sound from said enclosure to a plurality of individual listeners;

. the walls of said enclosure in a single horizontal plane spaced in front of said speaker whereby sound waves of substantially equal intensity are propagated toward all said ports.

10. An acoustic distributor in accordance with claim 2 in which said enclosure comprises a. a substantially cylindrical manifold member having a planar top surface on the peripherythereof,

b. a substantially bowl-shaped top member having a bottom surface contiguously engaging the top surface of said manifold member, and

c. a sealing ring formed of a resilient polymeric material clamped between the bottom surface of said top member and the top surface of said'manifold member, with said sealing ring having aninternal groove which engages the peripheral rim of the speaker for supporting the speaker in a horizontal plane within said enclosure in a manner such that sound conduction from the rim of the speaker to the solid walls of said enclosure is substantially obviated.

Claims (10)

1. In an acoustic distributor for use in classrooms and the like for transmitting sound waves from a single electro-acoustic transducer to a plurality of listeners without disturbing other nearby persons: a substantially cylindrical thick-walled enclosure formed of sound absorbing polymeric material and having an interior-toexterior attenuation characteristic for audio frequency acoustic waves of the order of about 60 decibels; a loudspeaker mounted within said enclosure and adapted to be electrically connected to a source of audio frequency signals for producing high intensity acoustic waves within said enclosure; a plurality of angularly spaced substantially cylindrical apertures extending radially outward through the walls of said enclosure in a single horizontal plane spaced in front of said loudspeaker whereby sound waves of substantially equal intensity are propagated toward all said apertures; a plurality of acoustic headsets, each including an elongated listening tube having at its input end a semi-rigid probe adapted to be inserted into any one of said apertures, for conducting sound waves from said one aperture to the person using the particular headset; a plurality of valve mechanisms mounted exteriorly of said thick-walled enclosure, respectively adjacent the outer ends of different ones of said apertures; with each valve mechanism being operable, in a direction substantially normal to the longitudinal axis of the adjacent aperture, from its closed position to its open position upon, and as a direct consequence of, the insertion of a listening tube probe into the associated aperture and being operative to exert a retaining force on the inserted probe whereby the probability of inadvertent disconnection of the headset listening tube from the enclosure is substantially reduced.

2. An acoustic distributor comprising: a thick-walled enclosure substantially impervious to sound waves; a speaker mounted within said enclosure and adapted to be coupled to a source of audio frequency electrical signals for producing high intensity sound waves within said enclosure; a plurality of sound conducting ports extending through the walls of said enclosure from an interior sound chamber adjacent the front of said speaker to the exterior of said enclosure; and slide-valve means mounted exteriorly of said enclosure adjacent each port and slidably operable, in a direction substantially normal to the axis of the adjacent port, from a closed position to an open position and vice-versa whereby sound leakage from said enclosure by way of ports not having listening tubes coupled thereto is substantially avoided.

3. An acoustic distributor in accordance with claim 2 in which: said enclosure comprises a substantially cylindrical manifold portion with said sound-conducting ports extending radially through the side walls of said manifold portion and being angularly spaced therearound in a single horizontal plane.

4. The acoustic distributor of claim 2 wherein each slide valve means comprises (a) a slide valve element which is reciprocally movable in a direction substantially normal to the port with which it is associated, and (b) spring means for resiliently biasing said element toward the closed position and contiguously adjacent and covering the exterior end of the port associated therewith.

5. The acoustic distributor of claim 4 wherein each slide-valve element is formed of a relatively soft and resilient polymeriC material and has a wedge-like configuration with the thicker portion below the associated port so that when the wedge-like valve element is moved upwardly by its associated biasing means, it wedges between the outer surface of the enclosure side wall and a peripherally encompassing base member to thereby substantially seal the associated port against undesired sound leakage.

6. The acoustic distributor of claim 4 wherein each of said ports is adapted to receive a hollow semi-rigid probe carried at one end of a headset listening tube and wherein each slide valve element is formed of a relatively soft and resilient polymeric material and has a wedge-shape configuration, with the slide valve element being contacted by said rigid probe and moved from the closed position to the open position upon insertion of the rigid probe into the associated port.

7. The acoustic distributor of claim 3 wherein said enclosure provides a sound intensity differential of the order of 60 decibels between the interior and the exterior thereof and wherein said slide-valve means comprises a plurality of wedge-shaped slide valve elements angularly spaced around the exterior of said enclosure, respectively overlying the outer ends of said ports, and eavh movable downwardly to accommodate insertion of a listening tube probe into its associated port.

8. An acoustic distributor in accordance with claim 4 and further including a plurality of sound tube headsets for respectively conducting sound from said enclosure to a plurality of individual listeners; with each of said headsets having a rigid probe carried at the input end of its sound tube and adapted for sliding the associated slide valve element from the closed condition to the open condition when said probe is inserted into one of the ports of said enclosure.

9. An acoustic distributor in accordance with claim 2 in which said speaker is mounted in a horizontal plane within said enclosure and in which said ports are angularly spaced around and extend radially through the walls of said enclosure in a single horizontal plane spaced in front of said speaker whereby sound waves of substantially equal intensity are propagated toward all said ports.

10. An acoustic distributor in accordance with claim 2 in which said enclosure comprises a. a substantially cylindrical manifold member having a planar top surface on the periphery thereof, b. a substantially bowl-shaped top member having a bottom surface contiguously engaging the top surface of said manifold member, and c. a sealing ring formed of a resilient polymeric material clamped between the bottom surface of said top member and the top surface of said manifold member, with said sealing ring having an internal groove which engages the peripheral rim of the speaker for supporting the speaker in a horizontal plane within said enclosure in a manner such that sound conduction from the rim of the speaker to the solid walls of said enclosure is substantially obviated.

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