US2065578A - Sound transmission - Google Patents

Description

Dec. 29, 1936. R N 2,065,578

SOUND TRANSMISSION Filed Aug. 14, 1935 6 Sheets-Sheet l KIM KW 19% ENTOR ATTURNEYS Dec. 29, 1936 R, R N 2,065,578

SOUND TRANSMI SS ION Filed Aug. 14, 1935 6 Shets-Sheet 2 4 hm; m g W Arroauzys Dec. 29, 1936.

R. R. GLEN SOUND TRANSMISSION Filed Aug. 14, 1955 6 Sheets-Sheet 3 INVENTOR Dec. 29, 1936. R. R. GLEN SOUND TRANSMISSION Filed Aug. 1.4, 1935 6 Sheets-Sheet 4 I A rg RN 2Y5 6 Sheets-Sheet 5 NV E-NTOR W /WUJM R. R. GLEN SOUND TRANSMISSION Filed Aug. 14, 1935 Dec. 29, 1936.

R. R. GLEN SOUND TRANSMISSION Dec. 29, 1936.

Filed Aug. 14, 1935 6 Sheets-Sheet 6 W /mv mm Efmmmli Patented Dec. 29, 1936 UNITED STATES PATENT OFFICE SOUND TRANSMISSION Application August 14, 1935, Serial No. 36,076

In Great Britain May 30, 1935 25 Claims.

This invention relates to a method and apparatus for modifying sound. It is frequently found desirable to modify sounds which are being electrically transmitted for recording or re- 5 production in order to provide a more pleasing or realistic final result. Thus, for example, it may sometimes be desirable to modify, in the recording of sound for use in combined sound and cinematograph records, the voice of an artist who is particularly suitable for the picture record but whose voice in its natural form is not suitable for the sound record. It is accordingly an object of the present invention to provide a method of modifying the tone quality of sounds being electrically transmitted for recording or reproduction and also to provide apparatus for use in this method.

The invention provides the method of modifying the tone quality of sounds being trans- 20 mitted as electrical impulses for recording or reproduction which comprises the steps of converting the electrical impulses into sound waves in a resonance chamber, adjusting the acoustic characteristics of the chamber and reconverting the sound waves into electrical impulses.

In one form of the invention the electrical impulses are converted into sound waves by means of a loudspeaker at one end of a resonance chamber of tubular form and are reconverted into electrical impulses by a microphone at the other end of the resonance chamber and the adjustment of the acoustic characteristics of the chamber is effected by varying its length.

Owing to the fact that a single loudspeaker is incapable of reproducing correctly the full range of sounds normally required for recording or reproduction it is preferred according to the invention to employ for converting the electrical impulses into sound waves two or more loudspeakers supplied from the same electrical circuit and having different sound reproducing characteristics suited more particularly to different parts of the sound range to be recorded or reproduced.

A further object of the invention is to provide a method and apparatus whereby sounds from a plurality of spaced sources may be satisfactorily combined for recording or transmission. A still further object is to provide in one form of the invention a method and apparatus whereby any desired balance in the combined sound of the sounds from the individual sources may be obtained.

The invention accordingly includes the method of combining for purposes of simultaneous re- (Cl. 181-B.5)

cording or transmission by electrical means sounds from a plurality of spaced sources which comprises the steps of converting the sounds from the said sources separately into electrical impulses, separately amplifying the electrical impulses corresponding to each source, separately converting the amplified impulses from each source into sound waves within a single chamber and re-converting the combined sound waves within the chamber into electrical impulses.

Preferably the electrical impulses corresponding to each source are separately amplified or modulated to an extent sufficient to produce the desired balance in the final combined sound.

A still further object of the invention is to provide a method and apparatus whereby the quality of sounds from several sound sources may be individually modified before the sounds are combined or whereby the quality of the combined sound may be modified after combination.

The invention includes apparatus for modifying the tone quality of sounds being transmitted as electrical impulses for recording or reproduction and comprising a chamber adjustable as to its acoustic characteristics, a soundreproducing device arranged to convert electrical impulses into sound waves within the chamber and a microphone arranged to pick up the sound waves within the chamber and to convert them into electrical impulses. In the preferred form of the apparatus the chamber is of tubular form and is adjustable in length to vary its acoustic characteristics, the sound reproducing device comprises a loudspeaker located at one end of the chamber and the microphone is located at the other end of the chamber. A plurality of loudspeakers may be employed within the chamber.

The invention also includes apparatus for use in combining-for purposes of simultaneous recording or transmission by electrical means sounds from a plurality of spaced sources comprising a plurality of microphones placed adjacent to the several sources respectively, ampliflers arranged to amplify the electrical impulses from each microphone individually, a chamber,

a plurality of loudspeakers each arranged to convert the amplified impulses from a different microphone into sound waves within the chamber, electrical connections between the microphones, amplifiers and loudspeakers and a microphone arranged to pick up the sound waves with in the chamber.

Some specific arrangements of apparatus according to the invention and the methods of using this apparatus will now be described by way of example and with reference to the accompanying diagrammatic drawings in which:--

Figure 1 is an elevation, partly in section of the apparatus employed in modifying the quality of sound from a single source,

Figure 1A is a view of a portion of the chamber shown in Figure 1 and illustrates a modification thereof,

Figure 2 is a modification of the arrangement shown in Figure l in which two loudspeakers are employed having different sound reproducing characteristics,

Figure 3 is a diagram illustrating the arrangement of the apparatus employed in combining sound from a plurality of separate sources,

Figure 4 is a view partly in section of the resonance chamber and associated loudspeakers employed in the arrangement shown in Figure 3.

Figure 5 is an end view of Figure 4 also partly in section,

Figure 6 is a longitudinal section of one of the loudspeaker extensions shown in Figure 4 and showing the relative internal diameters at intervals along the length of the extension,

Figure 7 is a section on the line 1-.' in

Figure 6,

Figure 8 is a section on a reduced scale on the line 8-8 in Figure 7,

Figure 9 is a view showing a spring used in the bayonet form of attachment between the extensions and the resonance chamber shown in Figure 4, and

Figure 10 is a part view of the chamber shown in Figure 4 and illustrating modified forms of the extensions.

Like reference numerals indicate like parts throughout the several figures of the drawings.

The arrangement shown in Figure 1 illustrates the application of the invention to the electrical recording on a photographic film of sounds produced on a film set. A microphone I is located on the set and is electrically connected to an amplifier 2 which is connected to a loudspeaker 4 disposed at one end of a closed cylindrical resonance chamber 6. The loudspeaker is of any suitable type, for example, that described in my copending application for Letters Patent of the United States, Serial No. 748,474 where the driven cone has a diameter of about 11 inches. The loudspeaker is detachably secured to the end of the resonance chamber by suitable means, such as a bayonet form of connection later described with particular reference to Figure 9. The resonance chamber itself is divided along its length into three parts I, 8 and 9 of which the two end parts 7 and 9 may slide within the centre part to adjust the length of the chamber, the parts being shown in Figure 1 in the extended position. In this condition parts 1, 8 and 9 have an overall length of about 42 inches and the chamber has a diameter of about 11 inches. A second microphone I0 is detachably secured at the closed end of the part 9 opposite to the loudspeaker and is connected through a suitable amplifier II to photographic recording apparatus l2.

In use the sounds to be transmitted or recorded are first translated into electrical impulses by the microphone I which then are amplified by the amplifier 2 to any desired extent and the amplified sounds are reproduced by the loudspeaker 4 inside the chamber 6. The sounds in the chamher 5 are picked up by the microphone I 0 and after suitable amplification are recorded on the photographic film. Tappings are taken at H to a monitoring device 16 whereby the operator can hear the sounds as they are being recorded and is able to adjust the quality of these sounds as is required by varying the length of the resonance chamber.

To provide a further means for adjustment of the final sound the loudspeaker 4 is arranged to be readily detachable for interchange with a loudspeaker which may be more particularly suited to an individual artist or sound source.

A further modification of the sound may be effected by placing a screen or screens I4, l5 (for example, of gauze) across the resonance chamber, and screens of different materials may be selected to obtain different results. Modifications in the final sound may also be effected by providing the parts I and 9 of the resonance chamber, with removable tubes, l1 and I8, of materials having any desired sound-absorbing qualities. One such material consists of asbestos fibres held by a bituminous binder others are gypsum, marble, cork, treated felt and wood which may be perforated or fitted with baffies. The portion 8 is also preferably provided with a wrapping of sound-absorbing material as shown .at 18, or by providing a jacket containing a liquid in a manner similar to that later described with reference to Figure 4. This jacket is shown at 30 in Figure 1A.

If desired, two or more resonance chambers and their associated microphones and loudspeakers may be employed for the individual modification of sounds from different sources which are subsequently to be combined. In certain cases the adjustment of the resonance chambers may be inter-connected so that a single control operates the adjustment of all the chambers.

In the modified form of this arrangement shown in Figure 2 two loudspeakers 3 and 4 are employed and are detachably secured to the ends of the arms of a tubular Y-shaped member 5 which is secured to the end of the resonance chamber 6 in place of the loudspeaker 4 shown in Figure 1. In this example the loudspeaker 3 (which is also of the type described in my aforesaid United States application Serial No. 748,474) has a driven cone of diameter of about 6% inches and is adapted to reproduce correctly sounds of high frequency while the loudspeaker 4 has a driven cone of diameter of about 11 inches and is adapted to reproduce correctly sounds of low frequency. f

The two arms of the Y are arranged to be of equal length. The loudspeakers are arranged to be readily detachable (for example, by means of a bayonet connection) from the Y-shaped member for interchange with loudspeakers which may be more particularly suited to an individual artist or sound source. Further, the Y-shaped member is arranged for ready detachment from the resonance chamber in order that it may be replaced either by a member of different form (for example, one having three arms and three loudspeakers) or by a single loudspeaker.

In the example illustrated in Figures 3 to 9 an arrangement is shown which is adapted for use in the photographic recording of sound. In order to record simultaneously and in satisfactory balance the sounds from a number of different spaced sources on the same set or even from different sets, or partly from the set and partly from a sound effects department, a plurality of microphones I are employed, each being placed adjacent to a source of sound (in this case five which may be for example a chorus, the effects department, a tap dancer, a vocalist and an orchestra). The electrical impulses from each microphone are separately amplified by means of individual amplifiers 2 and the amplified impulses are arranged to operate a set of loudspeakers 4 each corresponding to one of the microphones. These loudspeakers are all arranged to produce sound waves within a single closed chamber 20 at one end of which is a microphone ll] connected through suitable amplifiers to the photographic recording apparatus. The degree of amplification of each of the several amplifiers 2 is separately controllable so that any desired balance of sound from the various loudspeakers may be obtained within the chamber 20. By this arrangement it is found that the several sounds can be satisfactorily combined and at the same time proper and fully graduated control of the balance can be obtained.

In'this example the resonance chamber 20 has the shape shown in Figure 4 in section the chamber being of bulbous shape with an extending tubular neck and being a solid of revolution about the axis AA with five extensions 2| for the loudspeakers 4. These exten sions each have the internal shape shown in detail in Figure 6 in order to reduce reverberation at the entrance to the resonance chamber. The shape of the chamber and the character of the interior walls of the extensions are calculated and arranged so as to produce desired reflections, absorptions and resonance efiects, whereby predetermined modifications of the sound in the resonance chamber are acoustically obtained.

The microphone l may be axially adjustable along the mouth of the chamber if desired, and the extensions 2| (which are all identical) with their associated loudspeakers are each readily detachable from the resonance chamber in order that a loudspeaker especially suited to any particular sound source may be quickly inserted where desired.

The form of connection employed in this example is of the bayonet type and consists of three tongues 22 formed on the body of the extension and arranged to pass through openings 23 cut in a screwed ring 24 in engagement with a boss 25 on the resonance chamber, and, on rotation of the extension, to move under springs 26 (Figure 9) secured to the ring 24 up to an abutment 21.

As a further means of controlling, or modifying, the sound from one or more of the loudspeakers screens (e. g. of perforated metal, velvet or the like) may be inserted at 28 across the mouth of one or more of the extensionsthe extensions having a diametral slot cut, as indicated, for the reception of the screens. The

' slots are so arranged that the screens are infilling and emptying plugs 3| and 32. In use the jacket is filled with different liquids in order to obtain different results. Alternatively the chamber may be left unjacketcd and may be coated as required with suitable materials such as a mixture of asbestos fibres with bitumen.

If desired a tapping may be taken oil the leads from the microphone ID in order to provide means whereby the operator may hear the combined sound and when necessary effect adjustment to the controls.

When it is desired to modify the sounds from each source individually before they are combined the extension 2| may be replaced by tubular members which are variable in length. Ihis arrangement is shown in Figure 10 which illustrates a portion of the chamber 20 shown in Figure 4 with two of the extensions 28 replaced by extendible members 35. These members each consist of three portions of which the two end parts may slide within the centre part in a similar manner to the arrangement shown in Figures 1 and 2. In one case the member is provided with a single loudspeaker 4 and in the other case with a Y-shaped extension carrying at its end two loudspeakers 3 and 4 in a similar manner to the arrangement shown in Figure 2. The members 35 are attached to the resonance chamber by means of bayonet connections of the kind already described with particular reference to Figure 9. Screens l4 and I may be inserted across the members 35 in order to provide a further control of the quality of the, sound. It is to be understood that any number of the extensions 2| may be replaced by extendible members 35 in this manner and some of these members may have a single loudspeaker while others may be arranged to carry two or more loudspeakers as may be desired.

I claim:

1. The method of modifying the tone quality of sounds being transmitted for recording or reproduction which comprises the steps of initially converting the sound to be recorded into electrical impulses, converting the electrical impulses into sound waves in a resonance chamber, selectively modifying the acoustic characteristics of the sound waves within said chamber, and re-converting the modified sounds into electrical impulses 2. The method of modifying the tone quality of sounds being transmitted for recording or reproduction which comprises the steps of initially converting the sound to be recorded into electrical impulses, selectively amplifying said electrical impulses, converting the amplified electrical impulses into sound waves in a resonance chamber, selectively modifying the acoustic characteristics of the sound waves within said chamber, and re-converting the modified sound waves into electrical impulses.

3. The method of modifying the tone quality of sounds being transmitted for recording or reproduction which comprises the steps of initially converting the sound to be recorded into electrical impulses, converting the electrical impulses into sound waves in a resonance chamber of tubular form, acoustically modifying said sound waves in said chamber by varying the length thereof, and re-converting the sound waves into electrical impulses by means of a microphone located at the other end of the resonance chamber.

4. The method of modifying the tone quality of sounds being transmitted for recording o reproduction which comprises the steps of ini tially converting the sound to be recorded into electrical impulses, selectively amplifying said electrical impulses, converting the amplified electrical impulses into sound waves in a resonance chamber, modifying said sound waves in said chamber by adjusting the reflecting, absorbing and resonant characteristics of the interior walls of said chamber, and re-converting the sound waves into electrical impulses.

5. The 'method of combining for purposes of simultaneous recording or transmission by elec trical means sound from a plurality of sources which comprises the steps of converting the sounds from the said sources separably into electrical impulses, separably converting the impulses from each source into sound waves within a single chamber, and re-converting the combined sound waves within the chamber into electrical impulses.

6. The method of combining for purposes of simultaneous recording or transmission by electrical means sounds from a plurality of spaced sources which comprises the steps of converting the sounds from the said sources separably into electrical impulses, separately amplifying the electrical impulses corresponding to each source, separately converting the amplified impulses from each source into sound waves within a single chamber, and re-converting the combined sound waves within the chamber into electrical impulses.

'7. The method of combining for purposes of simultaneous recording or transmission by electrical means sounds from a plurality of spaced sources which comprises the steps of converting the sounds from the said sources separately into electrical impulses, separately amplifying the electrical impulses corresponding to each source to an extent sufficient to produce the desired balance in the final combined sound, separately converting the amplified impulses from each source into sound waves within asingle chamber, and re-converting the combined sound waves within the chamber into electrical impulses.

8. The method of combining for the purposes of simultaneous recording or transmission by electrical means sounds from a plurality of spaced sources and of modifying the quality of the sounds which comprises the steps of converting sounds from said sources separately into electrical impulses, separately amplifying the electrical impulses corresponding to each source, separately converting the amplified impulses from each source into soundwaves within a single chamber, adjusting the acoustic characteristics of the chamber, and re-converting the combined sound waves within the chamber into electrical impulses.

9. The method of combining for the purposes of simultaneous recording or transmission by electrical means sounds from a plurality of spaced sources which comprises placing a microphone adjacent to each of the sources, amplifying the electrical impulses of each microphone individually, converting the amplified impulses int-o sound waves within a single chamber by means of a plurality of loudspeakers each corresponding to a different microphone, and reconverting the sound waves within that chamber into electrical impulses by means of a microphone.

10. Apparatus for modifying the tone quality of sounds being transmitted as electrical impulses for recording or reproduction, comprising the combination with microphonic means for receiving and translating sound into electrical impulses, of a chamber adjustable as to its acoustic characteristics, a sound-reproducing device associated with said chamber arranged to convert said electrical impulses into sound waves within the chamber, and a microphone arranged to pick up the sound waves within the chamber and to convert them into electrical impulses.

11. Apparatus for modifying the tone quality of sounds being transmitted as electrical impulses for recording or reproduction, comprising the combination with microphonic means for receiving and translating sound into electrical impulses, of a chamber adjustable in size, a sound-reproducing device associated with said chamber arranged to convert said electrical impulses into sound waves within the chamber, and a microphone arranged to pick up the sound waves within the chamber and to convert them into electrical impulses.

12. Apparatus for modifying the tone quality of sounds being transmitted as electrical impulses for recording or reproduction, comprising the combination with microphom'c means for receiving and translating sound into electrical impulses, of a chamber adjustable in size to vary its acoustic characteristics and provided with a removable sound absorbing lining, a loudspeaker within the chamber, and a microphone also within the chamber.

13. Apparatus for modifying the tone quality of sounds being transmitted as electrical impulses for recording or reproduction, comprising the combination with microphonic means for receiving and translating sound into electrical impulses, of a chamber of tubular form and adjustable in length to vary its acoustic characteristics and provided with a removable screen and lining, a loudspeaker located at one end of the chamber, and a microphone located at the other end of the chamber.

14. Apparatus for modifying the tone quality of sounds being transmitted as electrical impulses for recording or reproduction, comprising the combination with microphonic means for receiving and translating sound into electrical impulses, of a resonance chamber adjustable as to its acoustic characteristics, a removable loudspeaker within the chamber, and a removable microphone also within the chamber.

15. Apparatus for modifying the tone quality of sounds being transmitted as electrical impulses for recording or reproduction, comprising the combination with microphonic means for receiving and translating sound into electrical impulses, of a tubular resonance chamber, a movable screen within the chamber and arranged to modify the acoustic characteristics thereof, a removable sound-reproducing device arranged to convert the electrical impulses into sound waves associated with one end of said chamber, and a removable microphone arranged to pick up the sound waves associated with the other end of said chamber and to re-convert said sound waves into electrical impulses.

16. Apparatus for use in combining for purposes of simultaneous recording or transmission by electrical means sounds from a plurality of spaced sources comprising a plurality of microphones placed adjacent to the several sourcesrespectively, amplifiers arranged to amplify the electrical impulses from each microphone individually, a chamber, a plurality of loudspeakers each arranged to convert the amplified impulses from a different microphone into sound waves within the chamber, electrical connections between the microphones, amplifiers and loudspeakers and a microphone arranged to pick up the sound waves within the chamber.

17. Apparatus for use in combining for purposes of simultaneous recording or transmission by electrical means sounds from a plurality of spaced sources comprising aplurality of microphones placed adjacent to the several sources respectively, amplifiers arranged to amplify the electrical impulses from each microphone individually and separately adjustable as to their degree of amplification, a chamber, a plurality of loudspeakers each arranged to convert the amplified impulses from a difierent microphone into sound waves within the chamber, electrical connections between the microphones, amplifiers and loudspeakers and a microphone arranged to pick up the sound waves within the chamber.

18. Apparatus for modifying the tone quality of sounds being transmitted as electrical impulses for recording or reproduction and comprising in combination a microphone located adjacent to a sound source, an amplifier, a telescoping resonance chamber adjustable so as to vary its acoustic characteristics, a plurality of loudspeakers within the chamber and having different sound-reproducing characteristics, electrical connections from the microphone and amplifier to the loudspeakers, and a microphone arranged to pick up sound waves within the chamber.

' 19. Apparatus for use in combining for purposes of simultaneous recording or transmission by electricalmeans sounds from a plurality of spaced sources comprising a plurality of microphones placed adjacent to the several sources respectively, amplifiers arranged to amplify the electrical impulses from each microphone individually, a chamber, a plurality of loudspeakers each arranged to convert the amplified impulses from one of the microphones into sound waves within the chamber, electrical connections between the microphones, amplifiers, loudspeakers, a microphone arranged to pick up sound waves within the chamber, reproducing apparatus, and electrical connection from the microphone to the reproducing apparatus.

20. Apparatus for use in combining for purposes of simultaneous recording or transmission by electrical means sounds from a plurality of spaced sources comprising a plurality of microphones placed adjacent to the several sources respectively, amplifiers arranged to amplify the electrical impulses from each microphone individually, a chamber, a plurality of loudspeakers each arranged to convert the amplified impulses from one of the microphones into sound waves within the chamber, electrical connections between the microphones, amplifiers, loudspeakers, a microphone arranged to pick up sound waves within the chamber, reproducing apparatus, electrical connections from the microphone to the reproducing apparatus, and a tapping from these connections to a monitoring device.

21. Apparatus for modifying the tone quality of sounds being transmitted as electrical impulses for recording or reproduction and comprising a resonance chamber of tubular form and adjustable in length to vary its acoustic characteristics, a Y-shaped extension on one end of the tubular chamber, two loudspeakers having different sound-reproducing characteristics and located respectively at the ends of the arms of the Y-shaped extension, and a microphone located at the opposite. end of the chamber from the Y-shaped extension.

22. Apparatus for use in combining for purposes of simultaneous recording or transmission by electrical means sounds from a plurality of spaced sources comprising a bulbous chamber having a tubular neck, and a plurality of tubular extensions from the bulbous portion, a loudspeaker at the outer end of each extension, and a microphone within the tubular neck.

23. Apparatus according to claim 22, in which the tubular extensions are provided with means whereby they are individually adjustable as to their acoustic characteristics.

24. Apparatus for modifying the tone quality of sounds being transmitted as electrical impulses for recording or reproduction and comprising in combination a chamber of adjustable length, a removable lining for said chamber arranged to vary the acoustic characteristics of the chamber, a sound reproducing device arranged to convert electrical impulses into sound waves within the chamber, and a microphone arranged to pick up the sound waves within the chamber and to convert them into electrical impulses.

25. Apparatus for modifying the tone quality of sounds being transmitted as electrical impulses for recording or reproduction and com prising a tubular chamber, a detachable and interchangeable tubular lining for a part of the chamber, a loudspeaker located at one end of the chamber, and a microphone located at the other end of the chamber.

ROBERT RODGER GLEN.

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