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A. J. SANIAL 2,301,459 Nov. 10, 1942

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A. J. SANIAL 2,301,459 Nov. 10, 1942 Nov. 10, 1942. A. J. SANIAL 2,301,459 ELECTRIC MEGAPHONE Filed Dec. 28, 1940 BY Patented Nov. 10, 1942 2,301.459 te UNITED STATEs PATENT OFFICE ELECTRIC MEGAPRONE Arar Y. Sania, Flushing, N. Y., assigner to Guided RadioCorporation, New York, N.Y., a corporation of New York Application December 28, 1940, serial No. 372,086 3 Claims. (C. 179-1) This invention is concerned with an electric which the loudspeaker unit and the tubular negaphone by means of which sounds, such as extension 2 are mounted. spoken sounds, supplied to one end of the device . A second annular wall forming member 3 is issue from the other end in greatly amplified secured at one end to the support 4 and extends votine. from that support back towards the support 3 but An object of the invention is the provision of terminates short thereof, as clearly shown in a simply controlled, portable device for use in Figure . The wall forming members 3 and 3 place of the ordinary negaphone and by means define an annular space 5 which forms a re of which a speaker's voice may be greatly ampli versely extending annular passage in communica fied and easily directed as required. O tion with the passage through the tubular exten Another object of the invention is the pro sion 2. Surrounding these elements is an outer vision in a single portable instrumentality, of a cylindrical or other suitably shaped housing combination microphone and loud speaker re which with the wall member 3 forms another Spectively associated so as not to cause any elec annular passage 8 which is in communication trical interference therebetween when intercon with the passage is around the end of the wall nected by means of an amplifier. member 3. At its other end the passage 8 is in A more general object of the invention may be communication with the atmosphere through said to be the provision of an electric megaphone the bell or flared end 9 of the housing . by means of which Sounds delivered thereto may As will be recognized, the members 2, 3, 3' be greatly annplified in volume. 20 and together form a folded horn, the entrance Other and more detailed objects of the inven to which is at the loudspeaker unit and the exit tion will become apparent from the following of which is at the mouth of the bel. By means detailed description of One embodiment thereof. of this construction a relatively long sound chan This invention resides substantially in the com nel is formed in a compact manner to provide bination, construction, arrangement and rela 25 the advantages and benefits of the much larger tive location of parts, all as will be explained in construction which would result if they were full detail hereafter. placed end to end. W in the accompanying drawing, referably the passage at the base of the beli Figure is 8 vertical, central, longitudinal, 9 is covered with , suitable porous or Screen cross-sectional view, with some parts in elevation, 30 member 6, behind which the parts are hidden of the combination nicrophone loudspeaker unit but without in any way interfering with the comprising part of the complete electric mega issing Sourad Waves. phone combination. interposed between the end wall of the housing Figure 2 is an elevational view of the complete and the annular support &, by means of an an unit comprising this invention. rular ange 6, is a cylindrica, housing is which As illustrated in, the drawing, the complete is open at both ends. The fange 5 is gripped combination of the invention includes a mega between these members by rubber gaskets 2 and phone unit made up of a microphone of any suit all of these parts may be secured together in any able type and a loudspeaker of any suitable type, suitable manner, such as by means of bolts or all enclosed within a housing constructed to pro 40. rivets (not shown). By this construction the vide a folded horn for acoustically amplifying and Various coapartments are sealed with respect to directing the issuing sounds. esch other and with respect to the outer atmos As illustrated, the device consists of a loud phere. speaker unit , of any suitable type such as a Mounted within the cylindrical housing 5 is a permanent magnet form, provided with a horn microphone 2 of any suitable construction. The consisting of a tubular extension 2 in the mouth periphery of the microphone housing is enclosed of which is secured a support, without come . within a tube 13 of any suitable material, such pletely obstructing the passage through the ex as a soft fibrous material. The microphone tension. Surrounding the loudspeaker unit is an housing 2 and the loudspeaker unit housing , annuitar Support provided with a cylindrical seat are spaced apart and interposed between them in on which one end of the annular wall member a thick disc or layer. of felt, is mounted at one end. The other end of this Likewise interposed between the housing 5 and annular tubular member 3 is secured to the end the microphone housing 2 is a gasket 4 of felt. of the tubular extension 2 in any suitable man The open outer end of the housing 5 is closed ner so as to enclose and seal the chamber within 55 of by a porous wall 8 which may be in the form 2 2,301,459 of a porous fabric or a metal screen. The sound vices being spatially 130 degrees apart, prevent receiving side of the microphone unit, of course, acoustical feedback between the two. faces the open end wall of the housing 5 so as In order to attain the object of this invention to be exposed to sound waves directed thereintp. in a practical way it is highly desirable that the Otherwise the microphone unit is completely. 5 loudspeaker unit be of the type which is markedly housed and Sealed and is so mounted as to be as directional.. The speaker and horn to be of a little subject as possible to disturbing vibrations. type which radiates most of the sound generated It will likewise be seen that by reason of the thereby substantially in a narrow cone from its gaskets 6 and 7, as well as fibrous tube 3. and mouth symmetrical with the axis of the horn. 0. In view of the fact that the directivity of a loud the felt Wall the microphone is Sound insul speaker tends to become less sharp at lower fre lated from the various passages within the horn, quencies, it is important that the frequencies and is also isolated from mechanical vibraticns radiated by the electric megaphone be limited induced by the loudspeaker unit in the entire to those in the frequency spectrum which are structure, as well. Thus an important and novel sufficient to permit intelligible speech to be feature of this invention is the space relationship 15 transmitted and yet are within the range of between the microphone and the loudspeaker and frequencies for which the horn maintains its the physical structure by means of which they are highly directional properties. By using a sharply incorporated into one unit, so that mechanical. directional loudspeaker one of the important and acoustical feedback between the two is objects of this invention is obtained. This ob eliminated. 20 ject, as previously referred to, is that of prevent Attached to the housing at any suitable place ing acoustical feedback between the loudspeaker as at the bottom, is a properly formed handle 9 and the microphone. Therefore, in addition to provided with an easily accessible finger oper placing these two devices so that they are 180 ated Switch 28 by means of which the apparatus degrees apart in space, a highly directional loud may be cut into and out of use. 25 speaker is employed, thereby minimizing any The general combinationisillustrated in Figure tendency to feedback acoustically. To re-em 2 wherein a portable amplifier of suitable type, phasize the point, mechanical feedback through such as a battery operated vacuum tube ampli the structure of the device is prevented by thor fier 22, is shown connected by a cable 2 with the oughly insulating the loudspeaker and micro necessary number of conductors to the micro 30 phone from each other against the transmission phone unit. As illustrated this cable extends to of vibrations therebetween through the struc the handle 9 and to the switch mounted thereon. ture of the unit. The insulating structural fea From it the individual conductors may extend to tures likewise serve to isolate the units from any and for connection to the microphone and loud direct airpath connections so as to contribute to speaker units in accordance with well known the prevention of acoustical feedback. practice. It will of course, be apparent to those skilled. Thus as will be readily understood, the micro in the art that in view of the fact that vacuum phone will be connected through the cable, 2 tube amplifiers of considerable amplifying power to the input of the amplifier, while the loud are available at the present time in small physi speaker will be connected to its output. The 40 cal units, that the amplifier may readily be in switch 20 may control the circuits in any suit corporated when desired directly in the electric able manner, as by simply interrupting the megaphone unit, whereby all the apparatus of microphone circuit when open or by interrupting this invention may be incorporated, when it is the energizing circuits for the amplifier when practical, in a single housing.
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