US2403231A

US2403231A - Reverberations modulator

Info

Publication number: US2403231A
Application number: US517321A
Authority: US
Inventors: Parisier Maurice
Original assignee: Individual
Current assignee: Individual
Priority date: 1944-01-07
Filing date: 1944-01-07
Publication date: 1946-07-02
Anticipated expiration: 1963-07-02

Description

Jul 2, 1946. M, PARBIER 2,403,231

REVERBERA'I'IONS MODULATOR Filed Jan. 7, 1944 2 Sheets-Sheet 1 Fl G. 1 38 36 34 53 29 37 Mug/c5 .PA Ava/ER INVENTOR ATTORNEY Patented July 2, 1946 BEVERBERATIONS MODULATOR Maurice Parlsier, New York, N. Y. Application January 7, 1944, Serial No. 517,321

Claims. (01. 179-1) My invention relates to sound conditioning for radio transmission and has particular reference to sound conditioning by means of acoustic reverberation chambers in which the sound is electrically reproduced, conditioned, and further transmitted for broadcasting or recording.

It is well known fact that quality of sound such -as music depends to a considerable-extent on the particular properties of the space, for instance, a hall in which the sound is produced. The sound is repeatedly reflected from the walls, producing a more or less lasting effect of reverberation which aflects the characteristics of the sound.

For obtaining the best acoustic results, music halls are usually specially designed to produce a uniform pleasing-effect of reverberation (without objectionable echo, however).

It has been found, however, that the particular type of a confined space, such as a hall, while it may be very effective for certain kinds of sound, for instance, for violins or chamber music, may be unsatisfactory for other kinds of sound, such as produced by wind instrument, organ, singing, etc, a

The reverberation effect depends on the physical dimensions of the confined space or hall, and to a considerable extent, on the surface of its walls, being difierent for smooth and rough surfaces, metal or wood, etc. Fabric (such as curtains) also considerably change the acoustic properties.

Reverberation effect is produced when a standing wave of sound is obtained in a confined space. When the sound is stopped, each individual mode of vibration will decay exponentially, and the combined eflect of the reverberation may be expressed by the formula:

' where V is volume of the room in cubic centimeters, a is a total room absorption=(A'a'+ A2a2+ A, A2 being areas in square centimeters, having coeflicients of absorption a, a2, etc.

It has been found that a hall, built to obtain the best results for one particular type of sounds, may not be satisfactory for other sounds, A hall, suitable for sounds of low frequencies, may be entirely unsatisfactory for sounds of high frequencies. For the best results in the sound transmission by radio, it is necessary therefore to find means to change the reverberation properties of the room in accordance with the variations in the types of sound.

Proper control of reverberation is particularly important in radio industry, for producing and recording music, speech, singing, etc., modulating the sound to suit particular requirements, so as to produce natural and most pleasing effects.

My invention has for its object to, provide means and method of sound transmission whereby the reverberation effect is produced artificially, by means of a chamber in which the sound is reproduced electrically and retransmitted also electrically after it has been modified acoustically in the chamber. The chamber or enclosure is so, constructed that its acoustic and. reverberationproperties can be rapidly changed at will, even during transmission of the sound. The chamber for this purpose is provided with movable or collapsible walls which can be operated at a distance, by an electric motor, for instance, for causingthe walls to collapse or to expand for varying the volume of the enclosure. For varying the other factor of the reverberation, i, e. sound-reflecting properties of the walls, the walls are made re-v placeable. operated by an electric motor, for instance, at a distance, so that one particular set of walls can be quickly replaced by another set, having different kind of surface. A plurality of telescopic walls may be provided for this purpose or, preferably, the walls may be made of a suitable flexible material, such as fabric, plastic, etc., mounted on rolls from which it can be stretched along the sides of the chamber. Different portions of the flexible material may have different finish or may be even made of different materials.

I have found that for the purpose of imparting particular acoustic properties to the sound by means of an adjustable acoustic reverberation chamber forming a part of a, sound transmission system, such a chamber may be of relatively small dimensions.

With proper adjustment, it is possible to obtain with such a small chamber the eflect of the sound as produced in a large concert hall, in an open space, etc. 7

A single artificial reverberation chamber may not be satisfactory, however, for transmitting mixed sounds in which sounds of widely different frequencies are used as, for instance, in the orchestral music, operas, singing, etc. Another object of my invention is, therefore, to provide means for independent conditioning of the sounds of different frequencies. I transmit for this purpose by electrical means through a series of acoustic reverberation chambers, each chamber being adapted to receive electric impulses corresponding to a particular band of frequencies. Each chamber is adjusted for producing the dethe desired final acoustic effect.

. ing reverberation chamber. are then recombined; means being provided to thereby.

Another object of my invention is to modify individually the volumes of the different bands of sound frequencies and to recombine these bands into a single transmission channel for obtainin For certain purposes it may be desirable to separate the sound into two main channels for transmission, one portion of the sound being directly transmitted through regular microphones and amplifiers, the other portion being separated into different bands of frequency, each band being then separately conditioned in a correspond- The two portions adjust the volume or amount of energy in each portion (and in each band) prior to their being combined together. The first portion, however, may be also divided into bands.

My invention is more fully described in the accompanying specification and drawings in which- Fig. l is a sectional elevational. view of my sound conditioning or reverberating chamber or enclosure;

Fig. 2 is a vertical sectional view of the same taken on the line 2-2 of Fig. 1; v Fig. 3 is a sectional elevational view of a modifled chamber; a

Fig. 4 is a diagram of connections of a radio transmission of sounds in which a series of my sound conditioning chambers is employed;

Fig. 5 is a fractional diagrammatic view of one group of reverberation chambers; and

Figs. 6 and 7 are diagrammatic views of modified acoustic chambers.

My reverberation chamber or enclosure l for sound conditioning, a shown in Figs. 1 and 2, in one of its practical embodiments, consists of a frame, preferably of a rectangular form, made of longitudinal bars 2, attached at the ends to

end walls

3, 4. These walls are stationary in the present instance and carry electrosonic conversion means, the wall 3 supporting a loud speaker 6 of an ordinary suitable type, and the wall 4 supporting a microphone I, also of a suitable ordinary type. The frame may be of relatively small dimensions. Brackets 8, 9, l0, H are mounted at the ends of the frame for shafts I2, l3, I4, l5 at one end of the frame and shafts l6, l1, l8, at the other end. (The fourth shaft is not shown in the drawings.) The shafts mount rolls of a flexible sheet material I9 such as fabric, plastic, thin sheet metal, etc., the material being stretched between the end rolls, forming walls of the enclosure I. The shafts I2, l3, l4, l5 are provided with bevel gears 22 at the ends, meshing with ears 23, and one of the shafts is also provided with a sprocket 24 connected by, a chain 25 with a sprocket 26 on the shaft of a motor 28. The shafts I6, l1, and H3 at the other end of the frame are provided with spiral clock springs 29 which keep the sheet niaterial under tension causing the motor to turn in one or the other direction, it is possible to wind the sheet material on one set of shafts, unwinding from the other, and to reverse the process by reversing the motor rotation. Each sheet consists of sections made of different materials, each section being of one particular material or having a particular'flnish.

The length of each section corresponds to the length of the frame. It is possible, therefore, by moving the sheets in one or the other direction to bring desired sections of the sheets over the sides of the frame, thereby forming a chamber with desired acoustic or reverberating properties. I have found that by changing the material of the walls of the reverberation chamber it is possible materially to change the quality orcharacter of the sound which is being transmitted by the radio.

The character of the sound or its'reverberation is also ailfected by the volume of the chamber. I provide for this purpose means to vary the volume at will, controlling from a central point both the type of thewalls and the volume of the chamber.

Forchanging the volume of the chamber, rolls 30 are provided at the main frame on shafts 3| hearing against the sheet material. The shafts are connected together by bars 20 and are. provided with braces 32, pivotally connected at 33 to levers 34, 35. The latter are pivoted at 36 to the brackets 8, 9 at one end of the frame, the other ends of the levers being connected together by bar 21 with nuts 31

engaging screws

38, 39 having right and left thread and rotated by a motor 40. By energizing the motor for rotation in one or the other direction, it is possible to move the levers together or apart, thereby compressing or releasing the walls.

As an additional arrangement for modifying reverberation properties of the chamber, I provide means to change the relative angular positions of the loud speaker and of the microphone. These instruments are mounted for this purpose on pivots 4|, 41 and are operated by small motors 52, i3.

A modified reverberation chamber is shown in Fig. 3. A frame 42 is slidably mounted inside a long tubular enclosure 44, the walls of the enclosure forming walls of the reverberation chamher, having a loud speaker 6 and a microphone 'l on the end walls 45 and 46. The tubular enclosure comprises sections, having different finish of their walls made of different materials. The frame 42 can be moved into any desired section by a motor 48, driving a belt 49, mounted on pulleys 50, 5|, the ends of the belt being attached to the frame 42, the return portion of the belt passing through suitable holes in the end Walls 45, 46.

My acoustic reverberation or sound conditioning chamber can be used for imparting any desired quality to the sound transmitted by radio as for broadcasting, recording, etc. Thus it is possible to modulate the sound of a musical instrument or orchestra to create an impression that the music is being played in an open space, in a large hall, in a small room, etc.

A single reverberation chamber, however, does not produce entirely satisfactory result for the reason that sounds of different frequency differently respond to the conditioning in a particular acoustic reverberation chamber. It is desirable,

therefore, to separate the sound into several through an amplifier 55 into' bus bars 56. One

portion of the total electric energy of the sound is transmitted directly throush an manner .01.

moans:

line 58, amplifier II, to theamplifier-mixer l0. The other portion of the sound energy is divided into different frequency bands, passing through amplifiers 8|, 82,13 and

through'reverberation chambers

68, 61, 88, from which the electric impulses are collected by bus'bars l8 and conduct- [various changes and further modifications may be made without departing from the spirit and ed to an amplifier 10 and to the mixer-amplifier 60. Potentiometers H, 1!, II, M are provided to regulate the relativeamounts oi enersy passing through the difl'er'ent branches of the transmission system.-

Similar potentiometers

15,18.

11 are provided at the amplifiers I and II, and for the amplifier B0.

Separation of the sound into bands of .diflerent frequency maybe accomplished mechanically or electrically. Mechanical means consists in the I adjustment of the volume of the reverberation changes and modifications.

crophone in the enclosure; a remotely controlled chamber whereby the particular chamber becomes responsive to frequencieswithin a certain range.

Adjustable chambers

88, 81, 68 are used for this urpose. They may be so adjusted that and reverberation chambers of constant volume The control motors '28, 40 of the reverberation chambers are connected by leads 82, 83, 84 with controller 85, 86. All the potentiometers for the branch lines and the motor control apparatus are placed on a control table where an operator can manipulate them in accordance with'the desired final eflect. Additional potentiometers 8l-may be provided between the microphones and the line 69. V

A more or less large number of reverberation chambers or enclosures may be used for radio recording or broadcasting. The chambers 88. 61, 68, 69, also 88, 61', 68', 69' may be connected in groups of a few as shown. in Fig. 5. each group containing several chambers. The microphone circuits are connected with potentiometers 92 for regulating relative strength of impulses from the individual chambers. A common potentiometer 94 may be provided for further adjustment of the individual signals before they are passed into

amplifiers

95, 96.

A modified acoustic reverberation chamber is shown in Fig. 6 comprising an enclosure 98 provided at the'sides with bypass ducts 89 and I00 with shutters l0l, I02 which can be adjusted to any desired degree of opening. The bypass ducts can be used to vary the volume of the chamber, and, also to divide the sound waves into several channels of diilerent length thereby adding novel acoustic effects. a

In another modification shown in Fig. 7 the enclosure 103 is provided with an additional chamber I04 at the side, having" ducts I 05 being directly opened into the surrounding space and provided with shutters I06. The open ducts modify the reverberation properties of the chamber. Movable piston-like members I 01'. may be also provided to vary the volume of the extension chamber.

In combining several acoustic chambers as shown in Fig. 4, the controls can be assembled in one place where an operator can manipulate contact points or switches arranged in the. form of 1 electric impulses.

a keyboard. A special music or other chart may be provided for guiding the operator.

It will be understood that variou features and rinciples of each of the embodiments of the in- 7,

in the art after understanding the invention, that scope or the invention, and it i intended there fore in the appended claims to cover all such What is claimed as new cured by Letters Patentis:

I claim as my invention: 7 1. A reverberation modulator comprising an enclosure having a wall made of a'flexible material; means to support a loud speaker and a mimotor at the enclosure; means to move said walls by the motor in a transverse direction for varying the volume of the enclosure, and means for passing said flexible wall in a plurality .of generally transverse directions to bring the various portions thereof from a gathered position as desired.

2. A reverberation modulator comprising a frame; walls movably supported at avplurality of sides of the frame having a series of interchangeable portions of different reverberation roperties along their length; a motor at the enclosure; means to move the walls by the motor lengthwise for placing portions or the walls with desired reverberation properties over the frame; and meansto support a loud speaker and a microphone in the frame; said moving means serving to interchange portions of said walls to bring one portion out of operative relation with said loud speaker and microphoneand to bring another portion into operative relation with said loud speaker and microphone.

3. Means to control reverberation in sound transmission by radio comprising a plurality of reverberation enclosures for loud speakers and microphones, each reverberation enclosure bei adapted to reproduce a sound of a limited band of frequency difierent from the' frequencies of the other reverberation enclosures; means to combine the electric impulses from different enclosures into a single channel; and means to modulate the reverberation in different enclosures by varying physical properties of the enclosures.

4. Means to control reverberation in sound transmission by radio comprising means to. convert sound into electric impulses; a plurality of enclosures forming reverberation chambers; means to separate from the electric impulses bands of selected frequencies and to direct the bands into the individua1 reverberation chambers; means to .convert the selected bands into sound in the reverberation chambers; means to modulate the sound by varyin physical properties of the reverberation chambers; means to convert the modulated sounds into electric impulses; and means to combine the electric impulses from the reverberation chambers with the unmodified 5. Means to control sound transmission com-. prising a plurality of reverberation enclosures; means to convert a sound into electric impulses of different frequencies; means to selectively reproand desired to be see position to an operative means; means: to individually vary the intensity 0! the electric impulses from different enclosures qualities and means move said movable set to interchange said. portions to bring one portion into voperative relation with said stationary wall portions and another portioncut of operative relation, with said stationary wall portions, said chamber having substantially constant volumetric characteristics during said change.

9. A reverberation modulator comprising a set otstationary wall portions,a set of movable wall diflerent frequency bands in different reverbera- "ticn chambers; modulating the sound in the chambers by varying by remote control-reverberation properties of the chambemiconverting' the sound in the chambers into electric impulses; in-

dividually modulating the impulses; and combining' the impulses from diflerent chambers into a single channel.

,7. A reverberation modulator comprising en- .closure means a wall of which has interchangeportions, 'electrosc'nic conversion means carried by one set, the various portions of the movable set having surfaces of varying sound'reflecting qualities. and power means Ior eflecting'accurate ,and measurable relative adjustment of said well and-said electrosonic means to interchange portions '01 said walliorming part of said enclosure to bring a portion 01' said wall out ot operative relationship' with said conversion means and to bring a .wallpcrtion having different reverberaable portions oi diflerent reverberation characteristics, electrosonic means, and 'means to im- I part relative movement to said wall and said electrosonic means to bring said electrosonic means and one portion or said wall out of operative relationship and to bring said electrosonic means and another portion oi said wall into operative relationship.

8. Areverberationmodulator comprising a set or stationary wall portions, a set or movable wall 'portio'ns, 'electrcsonic conversion means'carrled by one set. the various portions of the movable 'set havingsuriaces or varying sound reflecting tion' characteristics into operative relationship with said conversion means.

10. A reverberation modulatorcomprising a set of stationary wall portions, a set ct movable wall portions, electrosonic conversion means carried by one set, the various portions of the movable set I having surfaces or varying sound reflecting qualities, and remote control means ,to move said movable set relatively to said stationary set to remove one ot'the portions or said set and to bring into operative relationship another of the portions of said set;

v MAURICE PARISIER.