US2279018A

US2279018A - Sound recording method and system

Info

Publication number: US2279018A
Application number: US311518A
Authority: US
Inventors: Wallace V Wolfe
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1939-12-29
Filing date: 1939-12-29
Publication date: 1942-04-07
Anticipated expiration: 1959-04-07

Description

April 7, 1942. w, v. woLFE SOUND RECORDING METHOD AND SYSTEM Filed Dec. 29, 1939 3 Sheets-Sheet 1 JWM.

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April 7, 1942- w. v. woLFE SOUND RECORDING METHOD AND SYSTEM Filed Dec. 29, 1959 3 Sheets-Sheet 5 f c c Patented Apr. 7, 1942 SOUND RECORDING METHOD AND SYSTEM Wallace V. Wolfe, Beverly Bills, Calif., assigner to Radio Corporation o! America, a corporation of Delaware Application December 2s, 1939, serial No. 311,518 19 claims; (ci. 11s-100.3)

This invention relates to apparatus and methods used in the art of motion picture production and particularly to that part of motion picture production which is concerned with the recording and rerecording of sound concomitant with the picture.

It is well known in theart that motion pictures are made in a series of takes or sequences, the sound portion which nally accompanies the various sequences being rerecorded from several sources made either prior to or at the time of the taking or the pictures. The usual procedure is to make a picture sequence and simultaneously therewith make a synchronized sound sequence which will be composed of the dialogue, if any, occurring in the scene. Where certain picture sequences are silent, sound in some form of a musical selection may be .added to form a background for the action. Music may also be added to form a background for dialogue occurring in certain scenes. In many cases, sound eiects, such as hoofbeats, crowd noises, thunder. and the like, may be added to sequences with and without dialogue. These background sound eiects are generally taken from pre-recorded sound tracks and are mixed yto make a nal negative `from which will be printed the combinationpicture and sound lm suitable for theatre use.

The above procedure is known as rerecording, and is sometimes referred to as duping7 and dubbing." Each individual sound track sequence, such as the dialogue, the background music, hoofbeats, etc., are joined together into respective reels or in the form of individual continuous loops which are then run simultaneously through separate reproducers or soundheads. The output of each soundhead is combined in a common circuit, monitored and recorded during the synchronous projection of a reel of the related picture sequences. An operator known as the mixer has in front vof him on a panel a volume control for each of the sound reproducers. There may be one or more of these operators especially where several sound tracks are being combined. These mixers introduce the particular sound eiect at the proper point and control the volume of each sound to obtain the proper coordination and dramatic effect. No matter how skilled the mixer, it is necessary to rehearse. and usually the greater the number of sound tracks being combined, the larger the number of rehearsals. A rehearsal consists of reproducing the related sound track during the .simultaneous projection ofthe picturey and varying the volume controls to obtain the best combination and coordination of the various sounds as indicated on a loudspeaker monitor' system.

After the rehearsals have been made and the mixer and, perhaps, the director, who may be present, are satisfied that the last rehearsal will produce the desired combination effects, a .sound recorder is connected to the common output circuit from the mixing panel, and the mixer at tempts to repeat the last rehearsal while the sounds are recorded. However, as each rerecording rehearsal generally extends over the length of a reel, which isin the neighborhood of a thousand feet of lm, it becomes extremely difllcult to obtain an exact duplication of the last rehearsal. In most instances several portions of the final sound take may not compare in quality with that obtained during one or more of the rehearsals. Thus, it is either necessary to repeat the entire reel to correct or improve these poor portions of the sound recording and make an entire new recording with the attendant chances of other errors, or let the sound track go out with a quality below that which is possible. The present invention, therefore, is directed to a rerecording sound system wherein a special form of record of each rehearsal is recorded on a medium which will automatically and exactly reproduce all or any desired portion of a prior rehearsal while permitting the mixer to correct or alter all or any portion thereof during the process. That is, each rehearsal record is re' corded on a medium from which reproduction may be made immediately and during which the same record may be rerecorded on the same medium with corrected variations. After rehearsal is completed, the iinal take becomes completely automatic. Thus, as the various portions become perfected, they are exactly repeatable so that only the best combinations of sound eilects are obtained on the iinal negative. The system thus saves lm and time, and, most important of all, insures a higher'quality final sound track.

The principal'object of the invention, therefore, is to improve the methods of rerecording film sound tracks.

Another object of the invention is to record a form of control sound track during rerecording rehearsals which may be immediately reproduced for control of a subsequent rehearsal and which may be varied during the subsequent rehearsal.

A further object of -the invention is to duplicate the variations made inthe transmission of electrical currents and to enable changes to be made during the duplication and retransmission of the currents.

A further obiect of the invention is to record the control variation made in a rerecording channel during a rehearsal and reproduce, erase and rerecord the control variations. during a subsequent rehearsal.

A further object of the invention is to enable the best or any desired portions of a number of rerecording rehearsals to be duplicated or changed during the production of the ilnal record.

Although the novel features which are believed to be characteristic of this invention will be pointed out with particularity in the claims appended herewith. the invention itself, its objects and advantages, the manner of its organization and the mode of its operation will be better understood by referring to the following description read in conjunction with the accompanying drawings forming a part thereof, in which- Figure l is a diagrammatic arrangement of a single rerecording channel embodying the invention:

Figure 2 is a diagrammatic circuit arrangement of two rerecording channels embodying the invention; and

Figure 3 is a diagrammatic circuit arrangement of two rerecording channels embodying a modification of the invention.

Referring now to Fig. l, a sound reproducing system usually referred to as a soundhead is represented by a light source 5, lenses l and 1, and a photocell C. These elements are adapted in translate the sound track on a iilm l supplied from a reel Il and taken up by a reel Il. 'I'he film l is advanced past the translation point by a drive sprocket il driven by a motor Il. The variations in light impressed upon thel photoelectric cell l are translated into electrical currents which are fed into a variable gain ampliner Il. The output of this amplifier is impressed upon a standard ampliiier i1 feeding a standard recorder Il of any well known type. For the purpose of monitoring rehearsals and the final recording. a portion of the output of an amplifier i'l is impressed upon an amplifier 2l feeding a loudspeaker 2|.

In the usual rerecording system, a gain control is associated with the standard amplifier for varying the' amplitude of the transmitted currents in accordance with the mixers idea of what the proper sound level should be for the picture action. In the present system these variations in amplitude are accomplished in a different manner. A mixer panel shown at 2l contains a potentiometer, rheostat or resistance pad as indicated which will vary the amplitude of a constant frequency tone supplied trom an oscillator 2l through a switch 21 when the latter is in its left-hand position. The tone is rectined in a rectifier 2s and the direct current is applied to the control grid or grids of the tubes of the variable gain amplliler It which preferably employs variable mu tubes to provide a straightline variable gain characteristic. Thus. the present system employs an intermediate or secondary current source which is varied and which.

in turn. controls the amplitude of the currents in the rerecording channel.

In addition to the use of a secondary control current, the present system employs means for recording and reproducing the secondary current as modined by the mixer. This means is a magnetic wire recording system having a recording element Il connected through a switch Il intermediate the mixer panel 2l and rectifier Il. Reproduction from the wire Il is obtained from a pickup element 3l over conductors 34 through switch 21 when the latter is in its right-hand position. The record on the wire may be erased by an erasing element 3l under a control 30 positioned at the control mixing panel 2l. The lmagnetic wire recorder comprises a takeup reel 31 and a supply reel ll for the wire 39. and a driving motor 40 and a footage marker Il of any satisfactory type. The motor is under control of the mixer at l2. In operating the above system the soundhead motor I4 and ythe magnetic wire recorder motor I0 are synchronized and the wire is driven at the proper relative speed to maintain synchronism between the sound tracks at all times. The wire may be advanced synchronously by running it between driving rollers with a separate takeup reel or it may be in the form of a tape with sprocket holes therein. It may also be run at a relatively slower speed than the regular illm reproducer and recorder.

When the ilrst rehearsal is made, the switch 3| is closed and switch 21 is to the left, connecting oscillator 28 to panel 25. As the mixer operator varies the amplitude of the constant frequency tone from oscillator 28, and thereby varies the gain of the amplifier It to change the amplitude of the signal as indicated in the loudspeaker Il, a record of the constant frequency tone with its varying amplitude is made on the wire l! traveling to the left as indicated by the arrow on the reel l1. A certain start mark is made on the wire 3l at the beginning of the rehearsal and when the wire is rewound on reel 3l, the mark is set at pickup 33 instead of pickup Il for the second run. For the second run or rehearsal, switch 21 is thrown to the right, connecting pickup Il with the mixing panel 2l. Switch 3| may or may not be opened, as will be explained hereinafter. Should certain portions of the first rehearsal be considered satisfactory. the tone from the pickup 33 will automatically control the gain of amplifier Il according to the first rehearsal, the mixer keeping his dial fixed in position at panel 25. During this procedure the mixer may have switch 3l open and the eraser control inactive. If the switch Il is closed and the eraser control is active, then the same variations being reproduced may be rerecorded simultaneously.

During the reproduction, the mixer may change or vary certain portions of the first rehearsal, these changes being rerecorded at ll. It is thus obvious that the new record made by recording element 30 may be a combination of the rst volume variations which are erased at Il and rerecorded at 30, plus any modlncations made therein by the operator by adjusting his dial on panel 25. In this manner, the best variations in the sound obtained during a rehearsal are retained and are always repeatable without their being subject to human error. Thus, to make the final negative, it is only necessary to permit the pickup J3 to control the rectiiler 2l without any attention from the mixer, his control dial remaining iixed. It should be obvious, therefore. that only one film is required for the final recording, that the time required for rerecording is shortened, and that a better quality record is obtained.

Referring now to Fig. 2, in which a multiple channel rerecording system is disclosed, the rst channel comprises a soundhead 50 with its mo- :,avaois tor Il. a variable gain amplifier 52, a standard amplifier 33, and an individual monitoring circuit including an amplifier 04 and loudspeaker l0 with a control switch 56. vA recorder 59 is also connected in the circuit for operation when the negative is to `be made. The second channel is similar to the first and is composed of a soundployed, while the individual monitoring circuits.

may or' may not be used. There are occasions, however, when these individual monitors m-ay be used to advantage and, when so desired, may be simply connected by the

switches

56 and 65.

Similarly to the circuit of Fig. 1. the variable gain amplifier 52 is controlled by a rectifier 10, while variable gain amplifier 6| is controlled by a rectifier 1|. The input of each rectifier is connected to a mixing panel 13 having respective dials 14 and 15 for respective channels. Each rectifier is connectable to a separate oscillator of a different frequency, oscillator 1.1 being connected through a switch 18, when in its lefthand position, to rectier 1|, and oscillator 19 being connected to rectifier through switch 8| when in its left-hand position. The magnetic wire recording system is of the exact type shown in Fig. 1, and identical elements thereof have been given like numbers.

In the present system the constant frequency tones are applied to the same recording element 30, and although the frequencies have a non-harmonic relationship to decrease interference therebetween, bandpass filters 83 and 84 are used in the recording circuits controlled by respective switches 85 and 86 to aid in their segregation. 'I'he output of the pickup element 33 is also connected to bandpass filters 88 and 89 for the same purpose. The system of Fig. 2 operates basically in the same manner as the system of Fig. 1 except that the mixer now controls the ,two dials 14 and 15 during the rehearsal and there are thus recorded on the wire 39 two constant frequency control signals each varying in amplitude according to the manipulation of the respective dials. When repeating a rehearsal, the switches 18 and 8| are thrown to the right. In the operation of this multiple channel system, the eraser control functions in the same manner as in Fig. l, and with it effective, and switches 85 and 86 closed, the signal is rerecorded back on the wire 39. In the process, fixed positions of dials 14 and 15 will exactly duplicate the prior changes made in the channels, While changes may be made in one or both of the channels by adjusting the dials as was done during the prior run. Thus, a plurality of' rerecording channels may be automatically controlled in the manner shown in Fig. 2, additional channels requiring additional oscillators and filters. The wire recorder in this instance may be of the wide tape type wherein two recording elements record along parallel portions of the tape.

Referring now to Fig. 3, another method of recording, reproducing and rerecording the control tones for -a plurality of rerecording channels is shown, the main distinction between Figs. 2 and 3 being that only one oscillator is required for all channels in Fig. 3, but a magnetic recording system for each channel is necessary. In

Fig. 3, thel elements of the rerecording channels are omitted since they are the same as in Fig. 2,

while the elements common to Fiss. 2 and 3 have been given identical numbers. Thus, rectifiers 13 and 1| are shown connected to mixer panel 13 with its respective dials 14 and 15. In this modication, a single oscillator 9| is connected to the mixing panel 13 over channel switches 92 and 93 so that either rectier 10 or 1| may be connected to the oscillator, or the respective rectiiiers may be connected to their' respective magnetic wire pickups 91 and |04. The channel controlled by rectier 10 has the variations of the control tone impressed over a switch 95, when closed, on a recording element 96 of a magnetic wire recorder having the pickup element 91, a wire 98 and an eraser element 99 with its control |00. The channel under control of rectifier 1| has its control tone recorded, when switch |02 is closed, by recording element |03 of a magnetic wire recording system having the pickup element |04, a wire |05, and an eraser element |06 under control of the mixer at |01. The pickup element 91 is connected to switch 93 over conductors |08, while pickup element |04 is connected to switch 92 over conductors |09.

The operation of the system of Fig. 3 is substantially the same as that of Fig. 2 except that the equipment required in Fig. 2 is an oscillator and respective bandpass filters for each channel and a common magnetic recorder, while the system of Fig. 3 requires only one oscillator ior all channels, no bandpass filters, but a magnetic wire recorder for each channel. Each of the magnetic wire recorders has the necessary motor drives, footage controls, etc., as shown in Fig. l, and which are well known in the art. In each case, however, reproduction, removal of the recording, and rerecording of the control tone occur simultaneously, during which time variations may be made by the mixer to correct or improve certain parts of the sound record. In each case, also, whenit is desired to make a nal take, each channel is controlled automatically by the recorded control tone. 'I'he start marks placed at recording elements 96 and |03 when recording enable the wires to be reset at reproducing elements 91 and |04, respectively, when reproducing. Each rehearsal requires a new start mark, the distance between marks being equal to the distance between the recording and reproducing elements. Instead of two complete magnetic wire systems, a single wide-tape system may be used having plural recording and reproducing elements. In all of the systems, amplifiers may be used between the pickup elements and the mixing panels to obtain any desired level of the reproduced control tone.

Referring again to Fig. 3 there is shown connected to recording element 96 and pickup element 91, by dotted lines, a disc recorder and reproducer of the so-called instantaneous or immediate playback type preferably employing socalled acetate blanks. The recorder includes a driving motor for rotating a table ||2 upon which is a blank ||3. The cutter itself is shown at |I4 mounted on the lead screw ||5 in the assembly ||6. The reproducer includes a motor |20 driving turntable |-2| upon which the cut record |22 is placed. The pickup element is of the usual type mounted on the arm |23.

These disc recorder and reproducer units may be substituted for the various magnetic wire recorders shown in the different figures. In using this modification, however, it is necessary that as soon as the record is cut on the recorder it be removed and placed on the reproducer and a new blank positioned on the recorder. 4As subsequent rehearsals are made, the .output of the reproducer will control the gain ofthe re-recording channel in the same manner as described above. Changes may also be made in the course of the rehearsals. which will be recorded on a new disc. When the iinal take is to be made, it is only necessary to place the latest cut disc on the reproducer and permit the system to function automatically. Start marks are, of course, employed on the disc records. as it is well known in the motion picture soundondisc art, while the usual synchronizing system vfor driving the motors at synchronous speed may be employed. It is also to be understood that the use of film recorders and reproduoers could be used but without the advantages of the above-described preferred systems.

With the above-described systems, therefore, the best combination of dialogue, music backgrounds and sound effects derived during a rehearsal are always repeatable without reliance upon human memory or ability. This results in a higher quality iinal product than heretofore obtainable. A saving is also made in material and time of producing the ilnal combination negative for printing to the picture nlm. Recording of the currents in the channels themselves on the magnetic wire recorders or on the discs is possible but not recommended because the complex nature of the channel currents requires high quality equipment. The reproduced quality of a control tone such as a constant frequency from magnetic wire apparatus is very satisfactory, however, for'control purposes.

Although only two rerecording channels have been shown and described as illustrations, it is to be understood that more than two channels may be simultaneously controlled in a similar manner.

I claim as my invention:

l. In sound apparatus. the combination of a source of currents corresponding to sound waves, a transmission circuit for said currents. a variable gain ampliner for varying the amplitude of said currents in said circuit, means for generating a secondary current, means for varying the amplitude of said secondary current by impressing the products of rectification of said secondary current on said variable gain amplifier for varying the amplitude of said sound wave currents, independent means for recording only said secondary current, and means for reproducing only said secondary current to control the amplitude of said sound wave currents during a subsequent transmission of said sound wave currents over said transmission circuit.

2. Sound apparatus in accordance with claim 1 in which said recording and reproducing means function simultaneously to rerecord variations in the secondary current while said original secondary current automatically controlling the variation of said sound wave currents.

3. The method of obtaining the repetition of variations made in the transmission of electrical currents comprising making an individual record of the variations made during the transmission oi' said currents, utilizing said record for controlling the re-transmission of said currents. and making a second transmission record of said first record of transmission variations, said second record including variations made in the transmission of said currents during said re-transmission ci said currents.

4. The method of obtaining the repetition of the variable transmission of manually varied sound wave currents comprising recording the manual variations made during the transmission of said currents. controlling the re-transmission yof said currents by the reproduction of the re corded manual variations, and rerecording the reproduction of the original recorded manual variations together with subsequent manual variations made during the re-transmission of said currents.

5. Sound apparatus comprising a source of sound wave currents, a transmission circuit for said currents, a secondary source of current. means for varying the amplitude of said secondary current, means for connecting said source of secondary current to said transmission circuit for varying the amplitude of said sound wave currents in accordance with the variations of said secondary current, means for recording said secondary current, means for reproducing said secondary current, and means for connecting said reproducing means to said connecting means between said source of secondary current and said transmission circuitl said recording means being adapted to rerecord said secondary current during the reproduction thereof by said reproducing means.

6. Sound apparatus in accordance with claim 5 in which said recording and reproducing means includes a magnetic wire recorder and reproducer having separate recording and reproducing elements, said elements being adapted to function simultaneously {for recording said reproduced secondary current.

'1. Sound apparatus in accordance'with claim 5 in which said recording and reproducing means includes an instantaneous disc recorder and reproducer.

8. 'Ihe method of rerecording sound comprising reproducing a sound record, varying the amplitude of the reproduction of said sound record, recording the variations made in the amplitude of said reproduction, reproducing said recorded variations for controlling the re-reproduction of said sound record, and simultaneously rerecording said reproduced variations as originally recorded and as varied during the re-reproduction of said sound record.

9. In a rerecording system, the combination of a soundhead, a transmission circuit for said soundhead, a variable gain amplifier in said transmission circuit, a rectifier connected to said variable gain amplifier,` means for supplying a constant frequency current to said rectiner. volume control means for said constant frequency current; means for recording said constant frequency current, means for reproducing said constant frequency current, and means for connecting said reproducing means to said rectifier.

10. In a rerecording system, the combination of a plurality of soundheads, an individual transmission circuit for each soundhead, a variable gain ampliner in each transmission circuit, a rectier connected to each variable gain ampliiler, means for supplying a constant frequency current to each of said rectiilers, volume control means for said constant frequency current, means for recording said constant frequency current, means for reproducing said constant frequency current, and means for connecting said reproducing means to said volume control means.

1l. A rerecording system in accordance with claim 10 in which said constant frequency supply means is an oscillator, and` means are provided for selectively connecting said oscillator and said `and reproducer.

13. A rerecording system in accordance with claim 10 in which said constant frequency supply means comprises a single oscillator for said plurality of rectiers, and said recording and reproducing means comprises an individual magnetic wire recorder and reproducer for each of.

said rectifiers.

14. In a rerecording system having a, fader in-Y volving a movable manually operable control member adapted to control the amplitude of an electrical sound current, means for automatically repeating the variations in amplitude produced in said sound current by said fader comprising an ampliiler, means for producing a current proportional to the manual movements of said fader,

means foryarying the gain of said ampliiier by said movement current, means for recording said movement current, and means for reproducing said movement current for impression on said amplifier.

15. A system in accordance with claim 14 in which said movement current is recorded as re- Y produced, said fader varying said current as re'- corded. I

16. A rerecording system comprising a transmission circuit, an amplifier in said circuit, a source of current, manual control means for varying the amplitude of said current, means for impressing said current on said amplifier for varying the gain thereof, a recorder, means for simultaneously impressing said current on a recorder, and means for reimpressing said current when reproduced'y on said amplifier for varying the gain thereof in the same manner as when said current was. recorded. I 1'1. A rerecording system in accordance with claim 16 in which said reproduced current is rerecorded, said manual control means being adapted to vary the amplitude thereof as rerecorded. 18.' The method of rerecording comprising producing anelectrical sound current from an original sound record, audibly reproducing said sound current, manually eilecting desired amplitude modications in said sound current by reference to such audible reproduction, making a record of such amplitude modifications, producing an electrical sound current from said original sound record, repeating the same amplitude modications in said electrical sound current under the control of said amplitude modification record, and making a new record of such amplitude modifications variedby any additional manual variations made during the repetition.

. 19. The method of obtaining 'a control record for varying the amplitude of transmission of a signal current comprising audibly reproducing n said current, manually'efiecting desired amplitude variations in said current, making a control record of said amplitude variations, repeating said audible reproductions of said current and the amplitude variations thereof under control of said control record, and simultaneously rerecording said control record,said rerecorded control record being adapted to embody any manual amplitude variations made during the audible repetition of said signal current.

f WALLACEV. WOLFE.