US2079959A - Means and method for eliminating background noise in recording sound - Google Patents

Description

May 11, 1937. R. 5. FEAR 2,079,959

MEANS AND METHOD FOR ELIMINATING BACKGROUND NOISE IN RECORDING SOUND Filed Nov. 17, 1934 2 Sheets-Sheet l 4- 9 Q 2 m m: AMPLIFIER H 27 3 ELI I 5 RECORDER 9 1s IDEMHENETlZE R m I6 14 EU 1 F T UF' I'l'l AMPLIFIER AMPLIFIER INVENT OR.

May 11, 1937. R G FEAR 9 2,079,959

MEANS AND METHOD FOR ELIMINATING BACKGROUND NOISE IN RECORDING SOUND Filed Nov. 1'7, 1934 2 Sheets-Sheet 2 illllli jili w I 1|| m :1

p n i in 1 73 74 I INVENTOR.

Patented May ll, 1937 umreo STATE-S PATENT OFFICE MEANS AND METHOD FOR ELIIWINATING BACKGROUND SOUND NOISE IN RECORDING My invention relates-to a method for eliminating back ground noise in recording sound, more particularly to a new andnovel means foreliminating back ground noise when sound is recorded for use with motion pictures.

Hence one of the purposes of my invention is to provide means and method for eliminating back ground noise in sound recording.

Another object ofmy invention is to eliminate back ground noise in sound on wax or photographic type of recording.

Another object of my invention is to provide a time delay means, whereby an original sound may be delayed or stored electromagnetically or otherwise for a period of time sufilcient to enable controlling means to be actuated during such time delay.

All of these objects and others will appear to those skilled in the art of sound recording and 9 can be better understood by reference to the appended specification and drawings wherein like numerals indicate corresponding parts in the several views. r

Referring to the drawings.

Figure 1 is a diagrammatic view of the apparatus used to accomplish my purposes;

Figure 2 is an enlarged front elevation of the electromagnetically operated shutter;

' 'Figure 3 is a side elevation thereof;

30 Figure 4 is a diagrammatic view of the apparatus when used upon a phonographic disc recorder; and

Flgurefi isa vertical section taken'on the line 5-5 of Figure 4.

35 The several views illustrate one method of accomplishing my purpose wherein the means used is to translate sound or a record of sound into. varying electrical currents, to amplify said electrical' currents by conventional means such as by a vacuum tube amplifierfand then to magnetically record such electrical impulses upon a steel wire, belt or disc.

This is done by passing an endless steel wire belt, or disc moving at a constant speed between 4 two poles of an electric magnet.

This can be better understood by referring to Figure 1 where is shown a microphone i, the

output electrical current of which is fed by means of wires 2 and 3 into the amplifier 4, wherein the electrical currents generated by the microphone are amplified to a degree suitable for actuating the electromagnet 5, which is actuated by the amplified electrical currents that pass out of the amplifier 4 and thru feed wires 8 and An endless steel wire or belt 8 passes between the poles 9 and Ill of the aforesaid magnet and then around the two pulleys H and [2, one of which may be driven at a constant speed by any suitable means, not shown.

In the diagram (Figure 1) the endless steel wire or belt 8 is shown as passing around pulley H, then between pole pieces 9 and ill of the magnet 5, then around pulley l2, after which it passes thru and between the pole pieces l3 and l of the second electromagnet l5, then between pole pieces l6 and ll of a third electromagnet 18, then it passes thru another electromagnet l9 having pole pieces and 2|, after which it again engages pulley H thus completing the travel cycle aroundthe two-pulleys.

The electromagnet i5 is connected to wires 22 and 23, which are connected to amplifier 24, wherein electrical currents generated by the electromagnet I5 are suitably. amplified. 4

Wires 25 and 26 feed the output of the amplifier to the electromagnetically operated shutter 26a.

Referring to Figure 2:

'The electromagnetically operated shutter 260. has coils 21 and 28 that have cores terminating in pole pieces 29 and 30 and slots 3| and 32 into which the shutter leaves 33 and 34 are fitted. This shutter 26a being electrically operated only when a sound is recorded on the wire 8 prevents any noise to enter the recorder.

Referring to Figure 3 Frame 35 supports the two coils 21 and 2B, and

-is arranged with a hinge pin 36 to support the two shutter blades 33a and 34a. Springs 31 and.

.38 held to the frame 35 by screws 39 and 40 which hold the shutter in a normal closed position when the mechanism is not operating.

Again referring to Figure 1: i The electromagnet pick up i8, feeds current thru wires 4| and 42 into amplifier 43, where the varying currents generated by the pick-up 18 are amplified.

These amplified currents feed the light valve M, which maybe of identical construction to the magnetically actuated shutter 26a as shown in Figures 2 and 3.

An exciter lamp 45 which may burn at a constant intensity has a condenser lens 46 that focuses light onto the shutter of the light valve.

An objective lens 41 is arranged to pick up the light metered thru the shutter of the light valve and focus this metered light into the film recorder 48.

of film 50 is supported upon a spindle 5| and is led'down into the recorder where it engages with feed sprocket 52, being held thereon by holding means 58, after which it is led to recording sprocket 54, upon which it is held by engaging means 55. After leaving sprocket 54, the film 50 is led under tension roller 56, over guide roller 51, over recording shoe 58 and roller 59 and back onto recording sprocket 54, being held thereon by film sprocket engaging means 60, after which it is again led back onto feed sprocket 52, being held thereon by film engaging means 6|, and after leaving the feed sprocket 52 it is led or pulled out of the recorder by take up spindle 62 of the magazine 9.

The recorder may be mounted upon a base 63, and driven by a motor 64 arranged to rotate ata constant speed.

The operation of my invention as described in the above mentioned combination of elements, still referring to Figure 1, is as follows.

The microphone 8 picks up sound and converts the sound waves into electrical impulses. These are amplified by the amplifier 4, and

energize electromagnet 5 which in turn mag-- netizes the wire or belt 8 as it passes thru the aforesaid magnet and records sound thereon.

The wire 8 then passes around pulley l2 and between the poles of the electromagnet I 5 and the sound recorded upon said wire energizes said magnet, which then becomes a magnetic pick-up, causing electrical currents to flow into the amplifier 24. These currents are then amplified by the amplifier 24 to a degree powerful enough to actuate a relay and cause it to close. This relay which is embodied within the case of the amplifier 24, closes an electrical circuit powerful enough to actuate the electromagnet 26 and cause the shutter blades 33 and 34 to fly open./

The relay within amplifier is adjusted so that it will remain open as long as it is energized by any sound that may have been recorded upon the wire 8, which in turn is picked-up by the magnet l5, and sothat it will close when there is no recorded sound upon the wire 8.

As it takes a small fraction of time for the relay mechanism and the shutter mechanism 26a to operate, the re-recording pick-up I8 is located at a point remote enough so that the aforementioned mechanisms can be actuated by the-recorded sound before the sound recorded upon the wire passes into the electromagnetic pick-up l8.

When the sound recorded upon the wire has passed by the electromagnet l5, causing the magnetically operated shutter to open, and passes between the pole pieces l6 and ll of the magnetic pick-up 18, it causes electrical currents to be generated in the electromagnetic pick-up l8, and these currents after being amplifiedby the amplifier 43 actuate the light valve 44, thus metering the light emanating from the exciter lamp 45 and thus re-recording the sound, that had heretofore been recorded upon the steel wire, upon the film passing thru the film recorder.

After the sound recorded upon the wire 8 passes the pick-up l8, it passes between the poles of the electromagnet l9;

This magnet I 9 is energized by a battery 65 and mum magnetic record to affect the magnetic relay or this same condition may be adjusted in the amplifier 24 so that the shutter 26d will normally remain closed and only open when sound of a definite intensity has been recorded upon the wire. Hence it is possible to entirely eliminate any recording of low level sound that may havev been picked up by the microphone.

In the foregoing I have illustrated and described my invention when used to control the recording that is being done by a metering light valve, but it is obvious that a glow lampmay be substituted with equally satisfactory results.

My invention may-be used and actuated by recording from a wax record such as illustrated in Figure4 with exactly the same results.

It will be obvious that any degree of time delay desired may be secured by the above arrangement and that it is not necessary to synchronize the wire or disc recording mechanism with the recorder or its associated apparatus.

Referring to Figure 4.

The wax disc 66 is placed in the usual manner on a phonograph machine having uprights 61 and 68 the which the screw driving shaft 69 passes and at oneend of said screw driving shaft is attached the worm gear 10 actuated by worm H journalled in bracket I2 secured to the upright 61. This worm ll meshes with worm gear 13 secured on the driving shaft 14 of the motor 15, which driving shaft 'also operates the wax disc 66 at a constant speed.

A rod 83 is secured to the uprights 61 and 88 on which the recorder means to move as well as to steady the said movement.

The arm 17 carrying the pick-up I8 is pivotally secured at 84 to the frame of the machine and at the other end of said arm being provided with a hinged portion 19 to which the pick-up l8 means is attached.

A similar arm 80 carrying the noise reduction shutter pick-up 26a pivotally secured at 85 to the frame of the machine and at the other end of said arm being provided with a hinged portion 82 to which the noise reduction shutter pick-up is attached.

The wiringof these several parts are similar to the wiring descriptionof Figure 1.

While the details of the means and method for securing noise reduction in recording sound have I .been specially described in Figure 1, and one of the modified forms of construction shown in Figure 4, this invention is not confined thereto as other changes and modifications may be made without departing from the spirit and scope of my invention as defined by the appended claims.

What I claim is:

1. In an apparatus of the characterdescribed, a moving sound record medium, means for magnetically recording sound on the record medium, an electro-magnetle pickup-amplifier-relay operated shutter cooperative with the record medium and adapted to operate at a predeterminedsound intensity, and a second electromagnetic pickupamplifler-light valve recorder, also cooperative with said record medium for re-recording the sound on a second record medium. I

2. The apparatus as set forth in claim 1,.wherein the said second electromagnetic pickup is spaced from the first named electromagnetic pickup at a distance therefrom corresponding to a time delay interval necessary for of the amplifier-relay operated shutter.

3. The apparatus as set forth in claim 1, wherein a means is provided for de-magnetizing the the operation moving sound record medium following the sound re-recording 'operation.

4. The apparatus as set forth in claim 1, wherein the said movable sound record medium is in v 5. The apparatus as set forth in claim'l, wherein the said moving sound record medium is in the form 01 an endless flexible metal member and a means is provided to impart motion to the member at requisite speed for the effective re- 5 cording and re-recording of sound.

RALPH GORDON FEAR.

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