US2039173A - Sound record - Google Patents

Description

M 5 1936- N. LEVINSON 2,039,173

SOUND RECORD Filed June 24, 1955 mnnmmmw PEQU/QED 5OUND LEvEL (THEATEI? Sou/v LEVELS //v DB. ABOVE 0.006 WATT I -/0 A AUDIENCE NOISE LEVEL v NVE R. NATHAN LEVINSON THEATEIP NOISE LEVEL BY I ATTORNEYS.

Fuss.

Patented Apr. 28, 1 936 PATENT OFFICE SOUND RECORD Nathan Levinson, Hollywood, Calll'., asslgnor to United Research Corporation, Long Island City, N. Y., a corporation of Delaware Application June 24, 1935, Serial No. 28,029

2 Claims.

This invention relates to the recording and produced in a theatre without the necessity of the operators changing his fader settings or without changing the print transmission of the sound track.

This is accomplished by intercutting variable area and variable density sound tracks as here= alter described, low level sounds being recorded as a variable density track portion, and high level sounds being recorded as a conjoining variable area traclr portion.

For further details of the invention, reference may be made to the drawing wherein:

Fig. l is a plan view of a film negative having one well known noiseless variable area type of record.

Fig. 2 is a plan view of another type of well known noiseless variable area negative film record.

Hg. 3 is a plan view of a well known noiseless variable density type of negative sound record.

Fig. l is a plan view of a talking motion picture positive film according to the invention and showing aeombinaticn sound track comprising the high volume noiseless variable area and low vol= e noiseless variable density records arranged in series.

Fig. 5 is a graph showing the relation of increase in volume level or the sound track in i 4.

Fig. 6 is a schematic representation of sound and theatre noise levels.

Fig. 7 is a plan view of a positive film showing a modified combination sound track according to the invention.

As is well known, the best unmodulated print transmission for variable density recordings is approximately 20%. This value or" print trans mission results in minimum distortion and most pleasantreproduction of sound recorded.

The output level oi" a variable density print varies with print transmission so that if it is desired to reduce the output level, the print can be darkened, or it it is desired to increase the output level, the print can be lightened. Such a. change in 'print density isaccompanied by a, quality change which is hardly noticeable within the limit oi, say, 16 to 30% print transmission. When the print transmission is changed beyond these 5 points, however, the quality begins to sufler.

The fact that the output level oi a variable density print depends upon print transmission, has been known and used for a number oi years. m It is used to increase the efiectlve volume contrast of the recording; for example, the print transmission of the opening title music is usually increased to, say, 50%, with the result that it plays e db. louder in the theatre than a. normal print. In this way, an efiective 8 db. increase in the output level of the recorded sound is obtained.

While this additional output level is very desirable, it is undesirable to obtain it by increaslog the print transmission because the result of 20 increasing the print transmission is to corre spondingly increase the ground noise on the film as well as to cause an impairment in quality. Referring to Fig. 6 of the drawing, the normal volume required for the average theatre is about 25 (plus) 20 db., 0 db. being 0.006 watts. In such a theatre the theatre noise level due to equipment is about a -25 db. level. The average audl once noise is about 15 db. level as is shown by Figure 6. When the (plus) 20 db. level is secured from a variable density print, whose normal transmission is 20%, and whose percentage modulation is the film noise level using 8 db. noise reduction is -l6 db. or 1 db. below the audience noise. It can be seen that it the normal 35 percentage modulation is reduced. to say 30%, the amplifier gain would have to be increased approximately 2 db. to secure the required (plus) 20 db. level. The noise levelwould also be increased 2 db. to e. 1e db. level where it would 40 be louder than the audience noise and be heard. Therefore, in order to secure a recording in which the surface noise will not be hecwd in the theatre, we are restricted at present to use a normal modulation of approximately e955.

When a normal modulation of 40% is used, the a increase in volume due to lull% modulation is only 8 db., which is not suhlcient to give the re quired volume contrast in recordings.

At one time it was or on practice to cue the pictures, that is, the operator changed the amplifier gain settings according to a. cue to give the proper volume contrast. This method, however, could not be relied upon for accurate control of the volume. A more successful method of scourwith the satisfactory contrast in ing an additional loudness is by varying the print transmission thus allowing the picture in the theatre to be reproduced on a single ii'ader setting volume that is required by the action. This change in print transmission, however, results in a deterioration of sound quality. How these defects are overcome will now be described.

As is well known, a variable area track consists of clear film outlined by modulation whose density is very great, in fact, practically opaque. As a result, the unmodulated portion oi a variable area film consists of a sound track, one-half of which is opaque, and the other half oi which is transparent. Its normal unniodulated transmission, therefore, approidmately 50% or 2 times the optimum unmodulated transmission for variable density track.

This difierence in unmodulated transmission results in a variable area track of the same percentage modulation being reproduced at a level which is approximately 8 db. higher when run onthe same reproducing system as the variable density track. Thus, by intercutting variable density and variable area recordings, I secure an 8.'db. level increase without changing the iader setting. Therefore, I secure the same effect prevlously described, in which I increase the volume of a variable density print by increasing print transmission, but I secure it without any impairment in quality. 1

The developed negative shown in Fig. 1 may be recorded in any well known manner in which a beam 0! light moves laterally from one edge of the sound track to the other in accordance with the frequency and level of the sound impressed thereon, while Fig. 2 is a developed negative in which the light moves oppositely from a center line in accordance with the frequency and volume level of the sound being recorded. Fig. 1 may have an anti-ground noise component in which the exposed portion is decreased to an envelope of the sound waves following the peaks while the record of Pig. 2 may be of the anti-ground noise type in which at times of no signal no light is impressed upon the film during recording or upon the photosensitive device during reproducing. The antiground noise characteristics of the tracks in Figs.

' 1 and 2 may be obtained by biasing the mirror of the recording galvanometer as is well known, or otherwise.

In Fig. 3 the variable density type of recording is shown as a developed negative in which the different opaoities or transparencies are represented by lines of difierent thickness.

Let us assume that the recording is to be made of the opening music in a. picture, this opening music comprising high volume levels while the sound before and after is of a type having a particularly low volume. In that case the negative in aoeaive Fig. 3 may be employed as the record of the low intensity sounds while the negative in either l or 2 may be employed as the record of the high volume sounds. These negatives are then spliced together for printing.

In is a positive print resulting from the spliced negatives just mentioned. The graph .in 5 represents the increase in volume for this record section, point A representing the limiting volume level possible to record without distortion the variable density type of recording. For a further increase in volume the variable area type of recording is employed as illustrated beyond the point A. It has been found that a gain in undistorted volume of eight decibels above that attainable with 106% modulation of the variable density method is possible by this combination while the over-all sound reproduction is of a higher-quality than is possible with any one type alone. Since the positive emulsion has a gamma difierent from the negative gamma, developing of the combination print is possible without destroying the advantages attributable to each type of sound track.

7 shows a modified combination sound tracl; which provides a further increase of volume contrast. This increase is accomplished by reducing the width of the normal variable density track which is intercut with the variable area track; that is, if the normal variable density track portion is reduced in width to one-half, as shown at i, there will be a 6 db. level contrast between it and a full width variable density tracl; portion 2. Or, if the one-half width variable density track portion l is intercut with the variable area track of Figs. 1 or 2, the resulting volume contrast will be six plus eight or 14 db., without changing the percent of modulation, or the print transmission, or the amplifier gain. The reduction of the track width to obtain the one-half width portion i may be accomplished during duhbing in the course of making the master negative of the full width portion 2 and the reduced portion 1'], and this master negative together with the master negative of the variable area track portion, as illustrated, for example, in Figs. 1 and 2, are printed onto a single positive film to provide the combination sound track illustrated in Fig. 7.

Having thus described the invention, what is claimed as new and desired to secure by Letters Patent, is:

l. A sound film record having a variable density sound track portion for low volume sounds and a variable area sound track portion for larger volume levels of the sounds.

Z. A. sound film record having a normal width variable density track portion between a variable density track portion of less than normal width and a variable area track portion.

' NATHAN LEVDISON.

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