Title:
Sound recording method and system
United States Patent 2279018


Abstract:
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 the art that motion pictures...



Inventors:
Wolfe, Wallace V.
Application Number:
US31151839A
Publication Date:
04/07/1942
Filing Date:
12/29/1939
Assignee:
RCA CORP
Primary Class:
Other Classes:
29/DIG.28, 84/DIG.26, 360/13, 369/3, 369/4, 369/85, 381/63
International Classes:
G11B5/02
View Patent Images:



Description:

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 the art that motion pictures are made in a series of "takes" or sequences, the sound portion which finally accompanies the various sequences being rerecorded from several l sources made either prior to or at the time of the taking of 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 effects, such as hoofbeats, crowd noises, thunder. and the like, may be added to sequences with and without dialogue. These background sound effects are generally taken from pre-recorded sound tracks and are "mixed" to make a final negative from which will be printed the combination picture "and sound film suitable for theatre use.

The above procedure is known as rerecording, and is sometimes referred to as "duping" 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 circu't, monitored and recorded during the s-'nchronous projection of a reel of the related picture sequences. An operator known as the "mixer" has in front of 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 effect 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 of the picture 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 at0 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 is in the neighborhood of a thousand feet of film, it becomes extremely 5 difficult 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.

2.% 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 recorded 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 final "take" becomes completely automatic. Thus, as the various portions become perfected, they are exactly repeatable so that only the best combinations of sound effects are obtained on the final negative. The system thus saves film 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 reproso duced 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 in the transmission of electrical currents and to enable changes to be made during the duplication and retransmission of the currents.

A further object 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 final record.

Although the novel features which are believed to be characteristic of this invention will be pointed out with particularity in the claims ap- I pended 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 i n conjunction with the accompanying i drawings forming a part thereof, in whichFigure 1 is a diagrammatic arrangement of a single rerecording channel embodying the invention; Figure 2 is a diagrammatic circuit arrange- g ment 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. 3 Referring now to Pig. 1, a sound reproducing system usually referred to as a soundhead is represented by a light source 5, lenses I and 7, and a photocell 8. These elements are adapted to translate the sound track on a film I supplied 3 from a reel II and taken up by a reel II. The film I is advanced past the translation point by a drive sprocket I3 driven by a motor 14. The variations in light impressed upon the photoelectric cell I are translated into electrical cur- 41 rents which are fed into a variable gain amplifier I I. The output of this amplifier is impressed upon a standard amplifier 17 feeding a standard recorder II of any well known type. For the purpose of monitoring rehearsals and the final 4 recording, a portion of the output of an amplifier 17 is impressed upon an amplifier 20 feeding a loudspeaker 21.

In the usual rerecording system, a gain control is associated with the standard amplifier for M varying the amplitude of the transmitted currents in accordance with the mixer's 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 21 contains a potentiometer, rheostat or resistance Pad as indicated which will vary the amplitude of a constant frequency tone supplied from an oscillator 26 through a switch 27 when the latter is in its left-hand position. The tone is rectified in a rectifier 21 and the direct current is applied to the control grid or grids of the tubes of the variable gain amplifier II 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 modified by the mixer. This means is a magnetic wire recording system having a recording element 30 connected through a switch 31 intermediate the mixer panel 21 and rectifier 22.

Reproduction from the wire t3 is obtained from a pickup element 33 over conductors 34 through switch 27 when the latter is in its right-hand position. The record on the wire may be erased by an erasing element 15 under a control 36 positioned at the control mixing panel 25. The magnetic wire recorder comprises a takeup reel i7 and a supply reel 3i for the wire 39, and a driving motor 40 and a footage marker 41 of any satisfactory type. The motor is under control of the mixer at 42. In operating the above system te sohe soundhead motor 14 and the magnetic .5 wire recorder motor 40 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 0 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 film reproducer and re a recorder.

When the first rehearsal is made, the switch S31 is closed and switch 27 is to the left, connecting oscillator 26 to panel 25. As the mixer operator varies the amplitude of the constant frequency tone from oscillator 26, and thereby varies the gain of the amplifier II to change the 0 amplitude of the signal as indicated in the loudspeaker 21, a record of the constant frequency tone with Its varying amplitude is made on the wire 13 traveling to the left as indicated by the arrow on the reel 27. A certain start mark is I made on the wire 3 at the beginning of the rehearsal and when the wire is rewound on reel 31, the mark is set at pickup 33 instead of pickup 21 for the second run. For the second run or rehearsal, switch 27 is thrown to the right, con) necting pickup 33 with the mixing panel 21.

Switch 11 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 13 will automatically I control the gain of amplifier Is according to the first rehearsal, the mixer keeping his dial fixed in position at panel 25. During this procedure the mixer may have switch 91 open and the eraser control inactive. If the switch II is closed I 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 13.

It is thus obvious that the new record made by ' recording element 30 may be a combination of the first volume variations which are erased at 35 and rerecorded at 30, plus any modifications 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 33 to control the rectifier 28 without any attention from the mixer his control dial remaining fixed. 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 first channel comprises a soundhead 50 with its motor I1, a variable gain amplifier 52, a standard amplifier 53, and an individual monitoring circuit including an amplifier 64 and loudspeaker 55 with a control switch 56. A recorder 58 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 soundhead 59 with its driving motor 60, a variable gain amplifier 61, a standard amplifier 62, and an individual monitoring circuit including an amplifier 63, and a loudspeaker 64 with a control switch 65. There is also a monitor circuit common to both channels composed of an amplifier 61 and a loudspeaker 68 which is always employed, while the individual monitoring circuits 1l may or may not be used. There are occasions, however, when these individual monitors may 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 2( gain amplifier 52 is controlled by a rectifier 70, while variable gain amplifier 61 is controlled by a rectifier 71. The input of each rectifier is connected to a mixing panel 73 having respective dials 14 and 75 for respective channels. Each 2 rectifier is connectable to a separate oscillator of a different frequency, oscillator 71 being connected through a switch 78, when in its lefthand position, to rectifier 71, and oscillator 19 being connected to rectifier 70 through switch 3 81 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 3 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.

The 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 78 and 81 are thrown to the right. In the operation of this multiple channel system, the eraser control functions in the same manner as in Fig. 1, 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 74 and 75 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, the elements of the rerecording channels are omitted since they are the same as in Fig. 2, while the elements common to Figs. 2 and 3 have been given identical numbers. Thus, rectifiers 71 and 1 are shown connected to mixer panel 73 with its respective dials 14 and 75. In this modification, a single oscillator II is connected to the mixing panel 17 over channel switches 92 and 93 so that either rectifier 71 or S11 may be connected to the oscillator, or the respective rectifiers may be connected to their respective magnetic wire pickups 91 and 104.

The channel controlled by rectifier I7 has the variations of the control tone impressed over a i switch 95, when closed, on a recording element 96 of a magnetic wire recorder having the pickup element 97, a wire 98 and an eraser element 99 with its control 100. The channel under control of rectifier I7 has its control tone recorded, when 0 switch 102 is closed, by recording element 103 of a magnetic wire recording system having the pickup element 104, a wire 105, and an eraser element 106 under control of the mixer at 101.

The pickup element 97 is connected to switch 93 over conductors 108, while pickup element 104 is connected to switch 92 over conductors 109.

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 0 and respective bandpass filters for each channel and a common magnetic recorder, while the system of Fig. 3 requires only one oscillator for all channels, no bandpass filters, but a magnetic wire recorder for each channel. Each of the 5 magnetic wire recorders has the necessary motor drives, footage controls, etc., as shown in Fig. 1, and which are well known in the art. In each case, however, reproduction, removal of the recording, and rerecording of the control tone 40 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, when it is desired to make a final take, each channel is controlled automatically 45 by the recorded control tone. The start marks placed at recording elements 96 and 103 when recording enable the wires to be reset at reproducing elements 97 and 104, respectively, when reproducing. Each rehearsal requires a new 50 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 repro55 ducing 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 con60 nected to recording element 96 and pickup element 97, 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 65 a driving motor III for rotating a table 112 upon which is a blank 113. The cutter itself is shown at 114 mounted on the lead screw 115 in the assembly 116. The reproducer includes a motor 120 driving turntable 121 upon which the cut record 70 122 is placed. The pickup element is of the usual type mounted on the arm 123.

These disc recorder and reproducer units may be substituted for the various magnetic wire recorders shown in the different figures. In using 75 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. As subsequent rehearsals are made, the output of the reproducer will control the gain of the 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 final 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 sound-on-disc art, while the usual synchronizing system for driving the motors at synchronous speed may be employed. It is also to be understood that the use of film recorders and reproducers 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 final product than heretofore ob- 2 tainable. A saving is also made in material and time of producing the final combination negative for printing to the picture film. Recording of the currents in the channels themselves on the magnetic wire recorders or on the discs is possible but 3 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 con- 3 trol 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. 41 I claim as my invention: 1. In sound apparatus, the combination of a source of currents corresponding to sound waves, a transmission circuit for said currents, a variable gain amplifier for varying the amplitude of said 4. 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 5c 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 5 currents comprising making an individual record of the variations made during the transmission of 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 of 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 of said currents by the reproduction of the recorded 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 !0 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 circuit, said recording means :5 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 0 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.

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

8. The method of rerecording sound comprisSing 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-repro5 duction 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 rectifier, 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 amplifier in each transmission circuit, a rectifier connected to each variable gain amplifier, means for supplying a constant frequency current to each of said rectifiers, 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.

11. 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 reproducing means to said volume control means.

12. A rerecording system in accordance with claim 10 in which said constant frequency supply means comprises an oscillator for each of said rectifiers, each of said oscillators having a different frequency, and said recording and reproducing means for the frequencies of said oscillators comprises a single magnetic wire recorder 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 rectifiers, 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 involving 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 amplifier, means for producing a current proportional to the manual movements of said fader, means for varying the gain of said amplifier 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 reproduced, said fader varying said current as recorded.

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 on said amplifier for varying the gain thereof in the same manner as when said current was recorded.

17. 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 an electrical sound current from an original sound record, audibly reproducing said sound current, manually effecting desired amplitude modifications 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 modifications in said electrical sound current under the control of said amplitude modification record, and making a new record of such amplitude modifications varied by 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 said current, manually' effecting 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.

WALLACE V. WOLFE.