Nov. v10, 1942. - A. J. YSANIAL ' ' . 2,301,459 ELECTRIC MEGAPHONE Filed Dec. 28, 1940 “23 2 ~ ~ Amp/‘WRI-INVENTOR. 50min! Patented’ Nov. 16,11 2,301,459 ‘ ‘ 9 STATES \ rsNr ‘ OFFlCE 2,301,459 nnncrmc maarnona Arthur J. Sanial, Flushing, N. I, 'assignor to Guided mop Quotation, New York, N. Y., a corporation or New York, ‘ 7 Application December 28, 1940, Serial no. “2,08% _ _ _ , (01. 179-1) ‘ This invention is concerned with‘ an electric which’ the loudspeaker unit a and the tubular‘ megaphone by means of which sounds, such as _ ‘ extension 2 are'rnounted. spoken sounds, supplied to one end oi’ the device ._ A second annular wall forming member 8' is issue from the other end in greatly ampli?ed secured atone end to the support d and extends I volume. ' from that support back towards the support 5 but An object of the invention is the provision- of . terminates shortithereof, as clearly shown in a simply controlled, portable device for usein > Figure 1. The wall forming members 3 and ii’ place of the ordinary megaphone and by means de?ne an annular space 5 which forms a re of which a speaker’s voice may be greatly ampli versely extending annular passage in communica _ lied and easily directed as required. 10 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 instrumentallty, of a cylindrical or other suitably shape‘d' housing ‘l combination microphone and loud ‘speaker re-v 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 5 around the end of the wall nected by’ means of an ampli?er. 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 ?ared end 9 oi the housing ll. by means of which sounds delivered thereto may As will be recognized, the members 2, 3, 3’ be greatly ampli?ed in volume. ' . 20 and 7 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 oi the bell. By means detailed description of one embodiment thereof. of this construction a relatively long sound chum This invention resides substantially in the com‘ ' nel is formed in a. compact manner to provide ' bination, constructionuarrangement and, rela 25 the advantages and bene?ts oi’ the much larger tive location of parts, all as will beexplained in construction which would result ir'i'they were full detail hereinafter. placed end to end. In the accompanying drawing, Preferably the passage at the'base ‘of the bell Figure l is a vertical, central, longitudinal. - 9 is‘ covered-with a, suitable porous or screen cross-sectional view, with some parts in elevation, 3.0 member it, behind which the parts are hidden of the combination microphone loudspeaker unit but without in any wayv interfering with the comprising part otthe complete electric mega issuing sound waves. phone combination. 7 ' ‘ interposed between the end wall of the housing Figure 2 is an elevational view of the complete ‘l and the annular support 3, by means of an an ~ unit comprising this invention. -" nular ?ange it, is a cylindrical housing i5 which As illustrated in. the drawing, the complete ‘ is open at both ends. The ?ange it 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 rivets (not shown). By this construction the vide a folded born for acoustically amplifying and various compartments are‘sealed with respect to directing the issuing sounds; ‘ ‘ ‘each other andfwith respect to the outer atmos ‘As illustrated, the. device consists oi‘ a loud- - , phere. speaker unit 9, of any suitable type such as a . Mounted within the cylindrical housing I5 ‘is a permanent magnet form, provided with a horn microphone I? 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 com- . within a tube ‘i3 of any suitable material, such pletely obstructing the passage through the ex as a soft ?brous materiaL- The microphone ' tension, Surrounding the loudspeaker unit is an housing i2 and the loudspeaker unit housing I, annular support 6 provided with a cylindrical seat - are spacedv apart and interposed between them in on which one end of the annular wall member 3 . a thick disc or layer Ill ‘of felt. Q. is mountedat one end. ‘The other end ‘of this likewise interposed between th'éhousing I‘ and annular tubular member‘! is secured ‘to the end a the microphone housing “is a'gasket 4 of 'felt. of the tubular extension 2 in any suitable man The open outer end oi’ the housing I! is closed . her so‘ as to enclose and seal the chamber within 55. oil by a porous wall I! which may be in the form 2 i' , I 2,801,459 ' ' of a porous fabric or a metal screen. The sound vices being spatially ,180 degrees apart,- prevent receiving side of the microphone unit. of- course, . acoustical feedback between the two. faces the open end wall of the housing I5 so as In order to attain the object of this invention to be exposed to sound waves directed thereinto. in a practical way it is highly desirable that the Otherwise the microphone unit is completely loudspeaker unit be of the type whichis markedly ' housed and sealed and is so mounted asv to be ‘as directional“ The speaker and born to be of a ' little subject as possible to disturbing vibrations. ' type which‘radiates most of thesound generated It will likewise be seen that by reason of the ' thereby substantially in a narrow cone from its gaskets IE and H, as well as ?brous tube l3. and mouth symmetrical with the axis-\of the horn. .the felt wall H, the microphone is sound insu 10 In view of the fact that the directivity of a loud lated from the various passages within the horn, speaker tends to become less sharp at lower fre and ‘is also. isolatedv from mechanical vibrations quencies, it is important that the frequencies induced by the loudspeaker unit in the entire radiated by the electric megaphone be limited structure, as well. Thus an important and novel to those in the frequency spectrum which are feature of this invention is the space relationship 15 suf?cient to_ permit intelligible speech to be between the'mi'crophone and the loudspeaker and transmitted and yet are within the range ofv 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 Attached to the housing ‘l at any suitable place .i Ject, as previously referred to, is that of prevent ' 'ing acoustical feedback between the loudspeaker as at the bottom, is a properly formed handle l9 provided with an'easily accessible finger oper and themicrophone. Therefore, in addition to placing these two devices so that they are 180 ated switch 20 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 combination is illustratedin Figure tendency to feedback acoustically. To re-em 2 ‘wherein a portable ampli?er 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 ?er 22, is shown connected by a cable 2| with the _ oughly insulating the loudspeaker and micro— necessary number of conductorsto 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 l9 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. - I ' 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 ampli?ers of considerable amplifying power to the input of the ‘amplifier, while the loud are available at the present time in small physr speaker will be connected to its output. The 40 cal units, that'the ampli?er 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 byinterruptingf' this invention may be incorporated, when it is the energizing circuits for the ampli?er when practical, in a single-housing.