US2791628A - Sound device - Google Patents

Description

May 7, 1957 Filed June 22, 1953 w. R. EDMONDSON SOUND DEVICE 2 Sheets-Sheet 1 l N VE N TOE V/u IA 2 E anon/05m May 7, 1957 w. R. EDMONDSON 2,791,628

SOUND DEVICE Filed June 22. 1953 2 Sheets-Sheet 2 & IHPULSE I MIXER PICKUP l i 2 29 l F165 42' 21% fi ial Q 2/,

22 PECOPDER ECURDR a 2a I /0' INVLWTOE a WILL m/vEfmavflrw United States Patent Office SOUND DEVICE William R. Edmondson, Los Angeies, Calif.

Application June 22, 1953, Serial No. 363,304

4 Claims. (Cl. 179-1) This invention relates to the stereophonic recording and reproduction of sound, wherein directional components of a sound are recorded and reproduced separately in a manner intended to reproduce for the auditor, the directional characteristics of the original sound. The invention is especially adapted for the recording and reproduction of sound on film in the moving picture art, wherein sound is synchronized with movies.

In the efforts that have been made up to the present time to stereophonically record sound on film, the practice that has been accepted as necessary to the production of realistic effects, has been to provide a separate microphone and supporting boom on each side of the recording area (e. g. sound room) the microphone on one boom recording the sound projected from that side of the area and the microphone on the opposite side of the area recording the sound projected from that side of the area. The microphones are always spaced apart by many feet, usually the entire width of the sound room, so that the sounds which are projected at one side of the room are recorded largely by the microphone stationed on that side, the other microphone being sufficiently far away so as to respond to such a slight degree as to make only a faint record of the sound. The separately made sound records are subsequently brought together in a suitable manner on a sound track, from which the two sound records can subsequently be reproduced by separate loud speakers positioned, in the auditorium, at stations corresponding generally to the original recording stations of the microphone. The essential characteristic relied upon in such an arrangement for contrast between the intensities of the respective sound tracks, is the element of distance from the microphone, and it has hitherto been thought necessary to incorporate this characteristic into any stereophonic sound system in order to obtain satisfactory results.

The imagined necessity for having the separate microphone booins disposed at widely spaced stations has created problems in the recording operation, which the present invention aims to avoid. Specifically, the major object of the present invention is to provide an apparatus for stereophonically recording sound through the use of a plurality of microphones which can be grouped immediately adjacent one another and supported by a single boom so that they may always retain a pre-determined basic relationship to one another which eliminates to a large degree the necessity for skilled manipulation of the Several microphones in properly positioning them for recording. V

A further object is to provide a stereophonic sound recording apparatus utilizing a plurality of microphones mounted in such a manner that they must always maintain a certain predetermined basic relationship to one another, and yet capable of being adjusted in a manner to better adapt the apparatus to the changing requirements for recording close sound as contrasted to the recording of distant sound.

A further object is to provide a method and apparatus for stereophonically recording and reproducing sound with a distinct improvement in the results obtained, as contrasted to the results of prior eiforts.

Other objects will become apparent in the ensuing specifications and appended drawings in which:

Fig. l is a schematic view illustrating the method of. stereophonic recording characterizing the invention;

Fig. 2 is a side view of the microphone unit;

Fig. 3 is a front view of the microphone unit; and.

Fig. 4 is a front view of a modified form of the microphone unit.

Fig. 5 is a schematic illustration of a method of recording sound in accordance with the invention;

Fig. 6 is a view of a small section of sound record tape made in accordance with the invention; 7 Fig. 7 is a schematic illustration of a method of converting a two-track sound record into a three-track sound record in accordance with the invention; and v Fig. 8 is a schematic illustration of the method..of.re-. producing sound in accordance with the invention. .4

Referring now to the drawing in detail, I have indicated schematically, in Fig. 1, a pair of sound sources which are generally designated A and A. The drawing illustrates how the apparatus may be used, in one position, at B, .for recording sound at close range and in another position, indicated at B, for recording sound at a greater distance. The sound waves radiating from the sources A and A are indicated by the lines C and C in the one instance and by the lines c and c in the other instance.

In order to better illustrate the essential features of-the.

invention, the pairs of lines C and C indicate relatively narrow sectors of the sound waves radiatingfrom the respective sources, such sectors being those portions of the waves which are centered upon the area of reception by the recording apparatus. Since the sectors, as thus selected for illustrative purposes, are relativelyv narrow,

they may be regarded as directional beams, and will be referred to hereinafter as such.

The invention, in its simplest form, utilizes a. pair of microphones 10, 10" which are mounted in close proximity, the spacing being as close, for example, as the spacing between the ears of a normal human being. In

this respect, the invention is based upon the premise,

that it should be possible to obtain the same directional characteristics through the reception of two slightly divergent sound waves from a commonsource, into microphones that are spaced as closely as the human ears, to the same extent as such directional characteristicis attained by reception through the human ears, thus spaced; although it is to be understood that up to this point, no one has disclosed the possibility of obtaining this result.

Generally, the invention achieves the result by interposing between the microphones 10, 10', a barrier which is indicated generally at 11. The barrier 11 is of suflicient dimensions and is so placed between microphones 10 and 10 as to completely shield each microphone from a respective sound beam C or C (or c or c) .as the case may be. For example, in the full line position of the microphone unit shown in Fig. 1, microphone 10' is completely shielded from all direct waves in sound beam C coming from source A and at the same time microf phone 10 is completely shielded from all direct waves in" beam C coming from source A. This will be apparent upon viewing the relationship between microphone 10 and the side margins of barrier 11 as indicated by the side. The microphone 10 is completely included within the area embraced between these lines, which, on the far Patented May 7, 1957;-

verting the two track tape or film of Fig. 6 into a three track tape or film, indicated at 29. Such soundrecord may have tracks 24, 24 corresponding to the similarly numbered tracks of Fig. 6, and, in addition, a third track 24" comprising a record of the composite sound derived from the separately recorded sounds picked up by microphones 10 and 10'. For producing the third sound track 24", the invention may utilize a standard impulse mixer, designated 30, together with a pair of reproducing units, designated E and E (or a pair of reproducing circuits in a single reproducing unit) said reproducing circuits having respective pick-up heads 31, 31' actuated by the sound tracks 24, 24 of the respective records 22, 22'. The signals recorded by recording heads 31, 31', are transmitted to the impulse mixer through circuits 32, 32' and corresponding signals are taken from the mixer through circuits 33, 33' for actuating re-recording heads 34, 34' so as to produce the sound tracks 24, 24' of the triple track record 29. At the same time, a third signal is developed in mixer 30 by the mixing of the signals which are put into the mixer through circuits 32, 32', this third signal being delivered from the mixer through a circuit 33" to a recording head 34", which produces the sound track 24". Sound track 24 will reproduce a sound constituting a composite of the sound reproduced from tracks 24, 24'.

Fig. 8 illustrates the reproduction of sound from three track record 29, in an auditorium. A movie screen is indicated at 40. Dynamic speakers are indicated at 41, 41 and 41". Speakers 41 and 41' may be disposed at respective sides of the auditoritun as previously indicated. Speaker 41 is located centrally of the auditorium, in a suitable overhead position. Speakers 41 and 41' reproduce from sound tracks 24 and 24' and speaker 41" reproduces from sound track 24". Three recording heads 42, 42' and 42", responding to the respective sound tracks 24, 24' and 24", are employed in the reproducing apparatus. The image of the actor A of Fig. 5, photographed in connection with the recording of the actors voice, is indicated on screen at F. It may be noted that the image F is located to the right of the center of the screen, just as actor A was located'to the right of the microphone unit 10, 10' as viewed from the point of view of the recording and photographing station. Correspondingly, the more intense sound, recorded by microphone 10 and recorded on soundtrack 24, is reproduced by speaker 41 while the less intense sound is reproduced by speaker 41', and accordingly the auditor obtains the directional effect of the sound coming from a point to the right of center, i. e., from the image F.

Reference has been made above to the use of the invention in connection with sound movies. At this point it may be explained that the invention is equally applicable to television, wherein both sound and visual images are recorded at a distance, transmitted by wire or aerial routes and reproduced in a television receiver. In the application of the invention to television, the recording of the sound on track would be dispensed with in those situations where the transmission is direct, i. e., the situation commonly referred to as live shows. In such a situation the illustrated microphone unit will be used for binaural reception of the sound at the scene of recording, the sound being recorded simultaneously with the operation of the television camera and the television signals being transmitted in the conventional manner. The sound signal would, however, be split so that there would be two sound signals instead of only one, and the television receiver would be provided with dual sound reception circuits and with dual speaker units which in this instance would be located outside of the television cabinet, so that they could be disposed on opposite sides of the auditor. Alternatively, the speaker units could be disposed within the television cabinet but set apart several feet so as to beam their respective sound waves to the auditors along paths converging provide the directional effect.

A further important characteristic of the invention is the provision for adjustment to varying conditions of close reception and distant reception. In the full line showing in Fig. 1, illustrating the close-up reception, the microphones 10, 10' are disposed fairly near to the center of the barrier 11. This provides the proper shielding relationship between the barrier and the respective microphones with reference to the direction of the sound forces from the microphone unit. The microphones are disposed somewhat eccentrically for the reason that the microphone unit is not disposed on a common axis with the sound sources but is located forwardly of the common axis of the sound sources A, A. In the more distant reception illustrated in dotted lines, the microphones 10, 10, in accordance with provisions made by the invention, have been adjusted away from the center of the barrier 11 so as to be partially beyond the periphery of the barrier. For even more distant recording, the units might be actually disposed completely beyond the periphery of the barrier although it will be understood that from a practical standpoint it is possible to restrict the range of adjustment to limits wherein the limit positions of the microphone do not extend substantially beyond the ends of the barrier.

The mechanism for providing such adjustment com prises a slide 45 attached to the upper edge of the barrier 11 and a pair of slideways 46 which slidably receive the respective sides of slide 45. Slideways 46 may consist in portions of a clamp bracket 47 adjustably mounted on a boom 48 and adapted to be secured by a thumbscrew 49. Microphones 10, 10 are carried at the respective ends of a yoke 50 which is mounted in bracket 47 as illustrated. Thus both microphones may be retained in sufficiently so as to laterally opposed relation while barrier 11 is adjusted between them.

Fig. 4 illustrates how, for multiple directional mixed sounds, three microphones may be utilized for direct recording of three sound tracks (e. g., sound tracks 24, 24', 24"), the central microphone 10" being disposed between two barriers 11, 11 and the outer microphones 10, 10' being located to the outside of the respective barriers. Yoke 50a may be considerably longer than yoke 50, parts being shown broken away to illustrate length.

I claim:

1. Sterophonic sound recording apparatus comprising a pair of microphones; a sound arresting barrier, said barrier being of disc form and having convex, non-reverberatory side faces; a common support upon which said microphones and barrier are mounted, with the microphones spaced apart laterally and disposed on opposite sides of the barrier in symmetrical relation thereto so that each microphone may be shielded by the barrier from sound waves directly impinging upon the other microphone; said barrier having a thickness dimension, between said microphones, only a fraction of its major dimension in a plane normal to a line joining said microphones; and independent recording mechanisms, each including a recording head electrically connected to a respective microphone, a sound record device, and means for moving the sound record device in contact with the respective recording head so as to simultaneously record, on the respective record devices, sound tracks for the sound waves impinging on the respective microphones.

2. Stereophonic sound recording apparatus comprising a pair of microphones; a sound arresting barrier, said barrier being of disc form, having respective side portions of sound absorbent material, and horizontally elongated; a common support upon which said microphones and barrier are mounted, with the microphones spaced apart laterally and disposed on opposite sides of the barrier in symmetrical relation thereto so that each microphone may be shielded by the barrier from sound waves directly impinging upon the other microphone; said support including means connecting said microphones and barrier for relative horizontal adjustment between said barrier on the one hand and said microphones on the other hand; said barrier having a thickness dimension between said microphones, only a fraction of its major dimension; and said microphones being centered rearwardly of the longitudinal center of said barrier.

3. Apparatus as defined incl aim 2, wherein there are only two microphones and a single barrier.

4. Apparatus as defined in claim 2, wherein there are two barriers and three microphones, including a central microphone disposed between. the barriers and two outer microphones disposed respectively beyond remote sides of the barriers.

References Cited in the file of this patent UNXTED' STATES PATENTS 1,624,486 Fletcher E1; 21 Apr. 12, 1927 1,765,735 Phinney June 24, 1930 1,942,925 Jenkins Jan. 9, 1934 2,122,010 Savage et a1. June 28, 1938 2,520,798 De Boer Aug. 29, 1950

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