Sound level control system

Dec. 2, 1941.

G. M. BEST

SOUND LEVEL.CONTROL SYSTEM

Filed. Jan. 31, 1939

2,265,097

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Patented Dec. 2, 1941

2,265,097

UNITED STATES PATENT OFFICE

2,265,097

SOUND LEVEL CONTROL SYSTEM

Gerald M. Best, Beverly Hills, Calif., assignor to Warner Brothers Pictures, -Inc., a corporation of Delaware

Application January 31, 1939, Serial No. 253,905

Claims. (Cl. 179—100.3)

This invention relates to motion picture sound recording apparatus and particularly to a sound rerecording system wherein a plurality of sound records are simultaneously reproduced and recorded into a single composite sound record.

The general type of rerecording system wherein a group of sound reproducers are operated simultaneously and the outputs thereof fed through a mixing panel to a recorder is well known in the art. The present invention is an improvement of such rerecording systems in the manner of maintaining the input to the mixing panel at a constant average uniform level. In the recording of different concomitant sound sequences for the different picture sequences, usually dialogue, each sound sequence does not always have the same average level thereon. These differences in level may be the result of causes, such as different recording machines, since some sequences may be recorded simultaneously, different recording operators, etc.

For the rerecording operation, the different sound sequences are spliced together and serially reproduced through a single reproducing machine, the output of which is fed to the mixing panel. The result is an output in which the average sound level varies from sequence to sequence.

Although the mixing operator has control over the level in this particular channel, he is usually unable to give the necessary attention to it since he is striving to obtain certain dramatic effects by properly combining the outputs of the various reproducers into the final sound track as he views the picture which is being simultaneously projected. He must also attend to the introduction of the various background effects at the proper points in the picture and must maintain the proper balance between the dialogue and various background effects. Thus, if the inputs to his mixing panel are varying from time to time without notice, his mixing operation suffers.

The present invention, therefore, is directed to an automatic volume control located between the output of a reproducer and the mixing panel. In general, it includes an attentuator pad operated by a relay under control of a breaker box actuated by notches in the film which have been made near the various splices of the different sequences. The level of each sequence is noted on an index card and the relay control is set according to the levels indicated on this card.

An object of the invention, therefore, is to control the amplitude levels of reproduced sound from a sound record.

A further object of the invention is to automatically vary the amplitude level of various sound sequences between the output of a sound reproducer and a sound recorder in accordance 5 with the predetermined average level of the respective sound sequences being reproduced.

A further object of the invention is to maintain a uniform average level of sound output from a reproducer reproducing a record having a series 10 of sound tracks of different average levels.

Although the novel features which are believed to be characteristic of this invention will be pointed out with particularity in the claims appending herewith, the invention itself, its ob15 jects 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 drawing forming a part thereof, in which:

Figure 1 is a diagrammatic circuit arrangement embodying the invention; and

Figure 2 is a detail view of a portion of a sound film being rerecorded showing the film control element.

Referring now to Fig. 1, three sound film reproducers 4, 5 and 6 are illustrated, the films 7, 10 and 15 of which may carry different portions of the final sound to be recorded. For instance, film 7, being supplied from a reel 8 and SO taken up by a reel 9, may contain all dialogue, or a combination of dialogue and musical passages recorded during the shooting of the scenes. The film ί 0, supplied from a reel 11 and taken up by a reel (2, may contain certain types of background 35 effects, such as crowd noises and the like, while film 15, supplied by a reel 16 and taken up by a reel 17, may contain other types of background sounds, such as airplane noises, hoofbeats, etc.

The film 7 is reproduced through the usual type 40 of reproducing optical system comprising a lamp 20, lens 21 and photoelectric cell 22. Similarly, the film 10 is reproduced through optical system .23, 24 and 25; and film 15, through a similar optical system 26, 27 and 28. The outputs of cells ⁴⁵ 22, 25 and 28 are all fed to a mixing panel 30, over conductors 31, 32 and 33, respectively. On the mixing panel SO is shown a plurality of control knobs 35 which actuate impedances known as “mixing pots” for varying the amplitude of ⁵⁰ the currents from the cells 22, 25 and 28, the balance thereof being observed by the mixing operator in the monitor loudspeaker 36 connected over conductors 37.

As far as has been described, this is the gen55 eral type of rerecording system whereby the out

2,265,097 put of the mixer 30 is fed over conductors 38 into a recorder 39 for making a master negative 40, supplied from a reel 41 and taken up by a reel 42.

As mentioned above, in the making of sound negatives, the recording usually occurs at different times and under different conditions so that although an attempt is made to maintain a certain uniform recording level, it frequently happens that the average levels for the various sound sequences vary to a considerable degree. That is, one scene may be at 50% modulation, another at 60%, and another at 35%, etc. If these various levels were reproduced in the theatre, It would not only be annoying to the listeners, but certain sequences might even be eliminated by the background effects. It is realized, of course, that the “mixer” at panel 30 could control these levels to a certain extent, but this is difficult, as explained above. ·, The present invention, therefore, is adapted to automatically equalize the various sound levels from the film 7 before they reach the mixing panel 30. This is accomplished by providing a series resistance 47 and a shunt resistance 48, the amount of each inserted in the circuit between the photoelectric cell 22 and the mixer 30 being controlled by a shaft 50, operated by a bell crank 51, connected through a rod 52 with a control box 54.

The control box 54 is one of the magnetically operated type shown in the U. S. Patent 1,863,051 of June 14, 1932, to A. S. Howell. Briefly, it comprises a magnetic solenoid which, when energized, releases the rod 52 and allows it to take a position previously set by lever 55. A plurality of holes 50 is provided for setting the lever 55 in different positions in accordance with a previously prepared index card. As shown, there are ten holes provided, each of which varies the attenuation pad 47—48 two db. Thus, should the handle 55 be set at a certain position different from the one previously set, then upon energization of the solenoid, the mechanism will adjust itself to the pre-set position. Thus, after each trip, the lever is set to the next position, as shown on the index card which indicates the setting of the lever in the holes 58.

The solenoid within the control box 54 is operated by a breaker switch box 57 over conductors 58, this breaker switch being shown in Fig. 2 as a roller 60 mounted on an arm 61 and bearing against the edge of the film 64 under tension of a spring 62, contact being made or broken at point 63. The positive film 64 is notched as shown at 65 according to the position of the splices of the various sequences. As shown, a strip 67 is shown spliced to a strip 68, the strip 67 being shown with a higher level sound than the strip 68. In this case, the notch 65 is placed in a position so that it will energize the solenoid within the control box 54 and thus set the attenuator to a position set by the arm 55. Thus, the entire negative film will be prepared with notches to actuate the attenuator 47—48 in accordance with the levels of the various sequences. The index card is, of course, prepared from the differences in level of successive sequences. This card is given to the rerecorder operator, who will set the lever 55 after each energization, according to the indications on the card. Thus, in operating the present system, the dialogue or other sounds upon the film 7 will arrive at the mixer panel 30 at an average uniform level so that the “mixer” may devote his entire time to obtaining the proper dramatic effect of the combined sounds.

It is to be understood that the above-described equalization may also be applied to additional channels, such as 32 and 33. Also, other types 5 of control units, such as disclosed in U. S. Patent 1,474,409 of November 20, 1923, to Ο. B. Depue, may be used for control unit 54, such units using a plug board which may be pre-set for a plurality of consecutive sequences. With such a 10 unit, a full film reel could be reproduced without manual attention depending on the number of changes required and the capacity of the unit.