US1956081A

US1956081A - System for correcting sound records

Info

Publication number: US1956081A
Application number: US565790A
Authority: US
Inventors: Roy J Pomeroy
Original assignee: Individual
Current assignee: Individual
Priority date: 1931-09-29
Filing date: 1931-09-29
Publication date: 1934-04-24
Anticipated expiration: 1951-04-24

Description

Patented Apr. 24, 1934 ETE STATES PAT SYSTEM Fort coRitEC'rING SOUND RECORDS Roy J. Pomeroy, Los Angeles, Calif.

10 Claims.

This invention relates generally to sound recordation and reproduction; and it may be stated as a general object of the invention to provide methods and means for compensating the distcrtions which arise in the recordation and reproduction of sound. This case is a companion to prior applications entitled System for correcting sound records, Ser. No. 279,789, led May 22nd, 1928, Patent No. 1,828,940, issued Oct. 27, 1931, System for correcting sound records, Ser.

No. 279,799, filed May 22, 1928, Patent No.

1,828,941, issued Oct. 27, 1931, and System for correcting sound records, Ser. No. 565,571, iiled Sept. 28, 1931. The present invention may be considered in the nature of a simplication and improvement on the methods and systems described in said companion cases.

The invention is broadly applicable to any record of sound Waves, but is probably most conveniently illustrated and described in connection with the photographic type of record. The particular type of photographic record with which I have chosen to illustrate the invention consists of a shaded band of constant density, a variable outline representing the sound character and volume. It is to be understood, however, that the invention is not limited to that type of record in any sense, that type of record having been chosen for typical illustration only.

In recording and reproducing sound, distortions are always introduced by reason of nonlinear characteristics of the various units involved. In photographic recording, it is often true that the chief distortions are introduced in the reproducing system, and particularly by the speaking unit, the distortions of the recording system being relatively small by comparison, and the chief concern in such cases is therefore With the distortions of reproduction. v

It is therefore the general object of the present invention to provide improved and simplied means for compensating the distortions of recordation and reproduction, and especially the distortions of reproduction since in certain cases the distortions of recordation may be neglected.

The general method involves the making of a distortion corrected record, wherein the distortion characteristic of the system are added to the true sound characteristics, but said distortion characteristics are added in a reverse sense, so that the added distortion characteristics are compensatory of, or have a neutralizing effect on, the distortions which are introduced by the various units of the system. In the previously mentioned case, Ser. No. 279,789, thisA is accomplished by what may be termed a photographic method, wherein an original photographic record is made, and then reproduced as sound. 'Ihe distorted sound thus obtained is then photographically recorded, and a negative of the resulting distortion record is photographically combined with a negative record of the original sound to make a correction record, and this correction record is then finally photographically combined with an original record to make the distortion corrected record. In application Ser. No. 279,790, there is described a method which substituted for the photographic combining of the original and distortion records, the combining of electrical sound currents representing said records, Whereby there is obtained a resultant electrical current representing the differences of said records, or in other Words the distortion alone. A record of this distortion current is made upon a film, and said record is subsequently printed along with the original record, the result being sound record reversely corrected for distortion, similar to that obtained by the method rst mentioned. In application Ser. No. 565,571, there is described and is claimed a simplication of the last described method.

The present case is similar to the two cases last mentioned, in that there is obtained an electrical current representing the distortions introduced by the various units in the system, but instead of making a record of this distortion representing current, said current is combined with a portion of the current representing the original undistorted sound, or representing the sound distorted only by the recording system, and such combination is so el'ected that the distortionrepresenting current is added reversely to the original or undistorted current. That is, the distortion representing' current is added to the undistorted current in such a manner that there is 9 obtained a current which is distorted reversely tothe distortions resulting from passing through the various units of the system. This reversely distorted electrical current is then recorded, thereby producing a reversely distorted sound record. Upon reproduction or" said record, the distorting effects of the system then act, as in the previous cases, to bring the sound wave back to its original form for reproduction.

Reference is now directed to the accompanying drawing, wherein there is shown a simplified system whereby the invention may be practiced, and in Which:

Fig. 1 is a simplied diagram ofA a circuiting' and recording system in accordance with the invention;

Fig. 2 shows the original sound current;

Fig. 3 shows the distorted sound current;

Fig. 4 shows the current resulting from diiierentially combining the currents of Figs. 2 and 3; and

Fig. 5 shows the sound current obtained by differentially combining the current of Fig. 4 with that of Fig. 2.

In Fig. 1 of the drawing microphone M1 is shown connected by leads 10 and 11 to an emplier A1. Amplifier A1 and other amplifiers to be mentioned may be any suitable electrical or vacuum tube amplifiers adapted to amplify audiofrequency currents. The output leads 12, 13 of amplier A1 are connected to a glow tube G1 or other light Varying device. Positioned to beatfected by the light from glow tube G1 is a photoelectric cell P1, a light slit S1 being shown interposed between the glow tube and cell.

Leads

15, 16 from photoelectric cell P1 connect to an amplifier A2, and the output leads 22, 23 of amplii-ler A2 connect to a speaker H.

Microphone M1 picks up the original sound, and an electrical sound current is conducted therefrom by leads 10, l1 to amplifier A1, and after ampliiication is conducted by leads 12, 13 to glow tube G1. The electrical sound current in circuit l2, 13 represents the original sound and is distorted only by the units M1 and A1, and such distortions may be negligible as compared with other distortions in the system. Light rays are transmitted from glow tube G1 through slits S1 to aiiect photoelectric cell P1, and the resulting sound current from the photoelectric cell is conducted by leads l5, 16 to ampliiier A2, the amplied current passing to speaker I-I and there being reproduced as sound. The sound reproduced by speaker H is picked up by microphone M2, a sound current being conducted therefrom to an amplifier A3. The output leads 20 and 21 of amplier A3 then carry an electric sound current which is identical with that in output circuit 12, 13 of amplifier A1 except for having imposed thereon the distortions arising in glow tube G1, reproducing system P1, A2 and I-i, and sys-- tem M2, A3. The reproducing system P1, A2, l-I, must be one having characteristics identical with the one to be used in nal reproduction, and the system M2, A3 should be one having characteristics identical with the original system M1, A1, or one introducing little or no distortion. Fig. 2 shows the sound current wave 40 in the output circuit 12, 13 of amplifier A1, which wave has the distortions of recording units M1 and A1, and Fig. 3 shows the corresponding sound current wave 41 in the

output circuit

20, 21 of amplifier A3, the latter wave having, in addition to the recording distortions of units M1 and A1, the artificial recording distortions or" glow tube G1 and system M2, A3 and the reproducing distortions of system P1, A2, I-I. Wave 41 is shown at 41 in Fig. 2, superposed over wave 40, and the last mentioned distortions are represented by the difference between said waves.

These electrical sound current waves in

circuits

12, 13 and 20, 21 are now to be diierentially combined, and for this purpose connections such as leads and 61 may be made between said circuits. Circuits l2, 13 and 20, 21 are connected with such regard for polarity that their currents oppose one another, the resulting current then representing simply their difference, or in other words the total distortion of units G1, F1, A2, H,

M2, and A3. Potentiometers 64 and 65 are shown connected in the circuit for the purpose of so balancing the potentials that the sound current components can exactly neutralize, leaving simply the differential distortion representing current. In series with circuits 60, 61 are leads 62, 63 connecting to the input terminals of an amplier A4. With the sound current components neutralized in circuit 66, 61 the resultant distortion representing current in said circuit may consist of a current Wave such as indicated at 46 in Fig. 4.

There is then in the output circuit 70, 71 of amplifier A, an electrical current wave (an amplication of wave 45) representing the artiiicial recording and reproducing distortions resulting from glow tube G1, reproducing system P1, A2, H, and system M2, A3; and there is in output circuit 12, 13 of ainpliiier A1 an original electrical sound current, indicated at 40 in Fig. 2, distorted only by the recording units M1 and A1. These two currents are now to be differentially combined in such a manner as to produce a resultant sound current distorted reversely to the directions of the distortions introduced by the above named articial recording and reproducing units. For this purpose the following connections may be made: Leads l2, 13 are shown connected to a control aniplier A5, although this ainpliiier may not be required since the current in circuit 12, 13 is already in an amplifier state; and, when used, amplifier A5 merely fullls the function of controlling the amplitude level to match the amplitude level of the current in output circuit 70, 7l of amplier A4. The output leads 72, 73 oi varnpliner A5 and the output leads 70, 7l of amplifier A4 are shown connected together through balancing potentiometers 75 and 76 by means of a circuit 7 7, 73, and these connections are made with such regard for polarity that the distortions are subtracted, so to speak, from the sound current output of amplifier or in other words are added reversely to said sound current.

Thus the connections are so made that the two current waves oppose one another, and the result is that the distortion characteristics of the systern G1, P1, A2, I-I, M2 and A3 are subtracted from the sound current wave having the distortions of M1 and A1. In Fig. 5 there is indicated at 40 the outline of the sound current wave output of amplifier A5 (which wave corresponds to the wave illustrated in Fig. 2), and at 48 the resultant re- Versely distorted sound current wave obtained by the opposed combination of the two current waves in circuit 77, 78. It will be obvious by comparison with Fig. 4 that the distortions are subtracted from, or added reversely to, the sound current wave output of amplier A5. In series with circuit 77 78 carrying the reversely distorted sound current there is shown a glow tube G2, preferably of characteristics exactly like that of glow tube G1, before which travels an actinic iilm 80, a slit S2 being shown interposed between glow tube G2 and film 80. Elements G2 and S2 are conventionally illustrated as typical of any approved recording means. Film 8G thus takes a photographic record 82 oi the reversely distorted sound current wave (Fig. 5) oi circuit 77, 78, and this sound record 82 is likewise reversely distorted, as will now be fully understood.

It will be remembered that the output current of amplier A1 resulted from the differential combination of one current wave distorted by recording unit M1 and A1, and another current wave distorted by recording units M1, A1, G1, reproducing units P1, A2, H, and recording units M2 and A3, and that said output wave therefore involves the difference of the two waves,'or in other words the distortions of reproducing units P1, A2, H, and recording units G1, M2, and A3. This last current wave, having the distortions of the last named units, is then combined in circuits '77, '78 with a current wave having the distortion of M1 and A1, and the resultant wave is therefore a sound current wherein the distortions of units M1 and A1 are cancelled by the distortions of units M2 and A3, thus leaving a current wave reversely distorted by the remaining distortions, i. e., those of recording unit G1 and of reproducing units P1, A2, and H. In making record 82, the reverse distortions of G1, whatever they may be, are cancelled in passing through G2, and record 82 is therefore reversely distorted by reproducing system P1, A2 and H, all other distortions having been cancelled. Upon any subsequent reproduction of record 82 by a system having distortion characteristics like those of system P1, A2, and H, those characteristics will then act to correct the Waves resulting from the reversely distorted record by exact cancellation of the remaining reversely introduced distortions, thereby bringing the wave shape back toits original form for audible reproduction.

It may here be mentioned that in case of an appreciable time lag introduced in the artificial reproducing and recording systems, a corresponding time lag may be introduced to the sound current in circuit 12, 13 between the glow tube leads and the balance of the system by the use of usual 1 transmission line pads. Such provisions are well understood in the art and are therefore not illustrated.

While I have now illustrated and described certain specific means for carrying out an embodiment of my invention, it will be obvious that various changes in design, structure and system arrangement may be effected without departing from the spirit and scope of my invention; and it is therefore to be understood that all such .changes are contemplated within the scope of my invention as expressed in the following claims.

I claim:

l. The method of making corrected sound records, that includes producing a substantially une' 3 `distorted original electrical sound current of the 'original sound, audibly reproducing sound therefrom, such sound having the distortions of reproduction, producing an electrical sound current from the distorted sound, differentially comr .bining said last mentioned sound current with a 'portion of the substantially undistorted sound current in such a manner that the sound currents are neutralized except for a distortion-representing current, combining the distortion-represent- `ing current with a portion of the original sound vcurrent in such a manner as to obtain a sound current reversely distorted to the distortions of reproduction, and making a sound record from said reversely distorted sound current.

2. 'Ihe method of making sound records, that vincludes producing an original electrical sound current from the original sound, audibly reproducing sound from a portion of said original sound current, such sound having distortions of reproductions, producing an electrical sound current from said distorted sound, differentially combining said last mentioned sound current with a portion of the original sound in such a manner that the sound currents are neutralized except for a distortion-representing current, combining said distortion representing current, with a portion of the original sound current in such a manner as to obtain a sound current reversely distorted to the distortions of reproduction, and making a sound record from said reversely distorted sound current.

3. The method of making sound records, that includes producing an original electrical sound current from the original sound, audibly reproducing sound from a branch of said original sound current, such sound having distortions of reproduction, producing an electrical sound current from said distorted sound, differentially combining said last mentioned sound current with another branch of the original sound in such a manner that the sound currents are neutralized except for a distortion-representing current, combining said distortion representing current with another branch of the original sound current in such a manner as to obtain a sound current reversely distorted to the distortions of reproduction, and making a sound record from said reversely distorted sound current.

4. The method of making sound records, that includes producing an original electrical sound current from the original sound, such current having the distortions of its production from sound, audibly reproducing sound from a portion of said original sound currents, said sound currents having said above mentioned distortions and the total distortions of reproduction, producing an electrical sound current from said last mentioned sound current, said sound current having in addition to the distortion of the reproduced sound the distortion of its production from the distorted sound, differently combining said last mentioned sound current with a portion of the original sound current so as to obtain a resultant current representing the distortion of reproduction oppositely, combining said last mentioned current with a portion of the original sound current so as to obtain a resultant sound current reversely distorted by said distortions of reproduction, and making a record of said resultant sound current.

5. The method of making corrected sound records, that includes producing an electrical sound current from the original sound, producing from a portion of said sound current an electrical current representing distortions of reproduction, oppositely combining said distortion representing current with another portion of said original sound current so as to obtain a differential sound current distorted reversely by the amount of said distortions, and recording said last mentioned current.

6. The method of making corrected sound records, that includes producing an electrical sound current from the original sound, producing from a portion of said sound current an electrical ourrent representing distortions of recording and reproduction, oppositely combining said distortion representing current with another portion of said original sound current so as to obtain a differential sound current distorted reversely by the amount of said distortions, and recording said last mentioned current.

'7. The method of making corrected records, that includes producing an electrical sound current from the original sound, producing from a portion of said original sound current and by utilization of the distorting characteristics of the sound reproduction system an electrical current representing distortions of reproduction, oppositely combining said distortion representing SOI current with another portion of said original sound current so as to obtain a differential sound current distorted reversely by the amount of said distortions, and recording said last mentioned current.

8. rhe method of making corrected sound records, that includes producing an electrical sound current from the original sound, producing from a portion of said original sound current and by utilization of the distorting characteristics of the sound reproduction system an electrical current representing distortions of recording and reproduction, oppositely combining said distortion representing current With another portion of said original sound current so as to obtain a differential sound current distorted reversely by the amount of said distortions, and recording said last mentioned current.

9. A sound record modifying system, comprising means for producing an original electrical sound current from an original sound, means for distorting a portion of said sound current in accordance with the distorting characteristics of a sound reproducing system, means for diiTerentially combining said last mentioned distorted sound current with a portion of the original sound current, in such manner as to obtain an electrical sound current distorted reversely by the amount of the distortionsand means for recording said reversely distorted electrical sound current.

10. A sound record modifying system, comprising means for producing an original electrical sound current from an original sound, means for audibly reproducing sound fed by said original sound current, means for producing an electrical sound current from said reproduced sound, means for diierentially combining said last mentioned electrical sound current with a portion of said original sound current in such manner as to neutralize said currents with the exception of a resultant electrical current representing distortions of reproducing and picking up the sound, means for negatively combining said distortion representing current with a portion of said original current in such manner as to reversely distort said current, and means for recording said reversely distorted current.

ROY J. POMEROY.