Acoustical System Employing Tubular Resonators

Abstract

Improved dispersion of the sound from an orchestra toward an audience and reinforcement of the lower frequencies in said sound are achieved through the use of tubular resonators positioned around and above the orchestra. Resonating chambers are formed in the ends of the tubes by means of transverse partitions. Electrically-driven speakers may be positioned in said tubes.

Description

BACKGROUND OF THE INVENTION

It is frequently the case that in an auditorium where an orchestra is to perform for an audience, the acoustics may be such that certain frequencies or ranges of frequencies may be reinforced or may be diminished to such an extent that the sound of the orchestra, as heard, is seriously impaired. This unbalance may be the result of designing the enclosure principally for speech. For the understanding of speech it is desirable that low frequencies be reduced; this is effected by the use of dropped acoustic ceilings and perforated ply-wood panels. The same effect is noted in large halls.

Need for bass reinforcement may also arise where the orchestral performance is to be recorded. Some widely-used types of microphones have low efficiencies at the lower frequencies so that again bass reinforcement is needed.

The need for improved dispersion of orchestral sound arises, particularly, where the wall at the rear of the stage is parabolic in shape. The output of instruments close to the focus of the parabola is projected directly forward whereas the sound from instruments away from the focus is projected to one side or the other. As a result, there are so-called deadspots on the stage. Devices to eliminate such deadspots and improve the dispersion of the sound produced are therefore necessary.

Devices for the improvement of dispersion are also needed for open-air performances. Without the means to assure dispersion in the proper directions, a major portion of the sound output is lost.

SUMMARY OF THE INVENTION

The present invention relates to a device for improving the dispersion of sound toward an audience from an orchestra on a stage, and for reinforcing low frequencies in the spectrum of said sound during the initial portion of reverberation. Vertical tubes are located on the stage at the sides and rear of the orchestra and horizontal tubes are supported above the stage in a direction transverse to the stage and the orchestra. Some of the vertical tubes have chambers formed at the upper open end of a tube by a transverse partition. Also, some of the horizontal tubes have chambers formed at each open end of the tube by transverse partitions. The lengths of the chambers in the different tubes vary in approximately equal steps from about 1/4 of the wave-length of the highest frequency to be reinforced to about 1/4 of the wave-length of the lowest frequency to be reinforced.

The upper ends of some of the vertical tubes may be cut at an angle in order to broaden the band of wave-lengths reinforced by the tubes. The same may be done with the ends of some of the horizontal tubes. The tubes may be used to house loud-speakers.

Accordingly, it is an object of the present invention to provide improved means to reinforce desired frequencies in the spectrum of sound produced by an orchestra.

Another object of the present invention is to provide means to improve the dispersion of sound produced by an orchestra in order to avoid loss of sound energy to regions not occupied by an audience.

A further object of the present invention is to provide means to produce reinforcement of sound in the lower frequencies without the need for supplying electrical energy.

Still another object of the invention is to achieve reinforcement of desired frequencies and improved dispersion of sound with a low cost device.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWING

For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawing, in which:

FIG. 1 is an elevational view of a stage and reflecting shell showing the disposition of vertical and horizontal tubes for reinforcing and dispersing sound in accordance with the invention;

FIG. 2 is a plan view in partial section of the shell and tubes of FIG. 1;

FIG. 3 is a view taken along line 3--3 of FIG. 2;

FIG. 4 is a view taken along line 4--4 of FIG. 2;

FIG. 5 is an elevational view in cross section of a vertical tube showing the mode of establishing the length of a reverberation chamber; and

FIG. 6 is an elevational view in cross section of a vertical tube wherein the open end of a reverberation chamber is cut at an angle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention, the dispersion of sound from an orchestra performing on a stage to an audience is improved by suitable disposition of large vertical tubes at the back and sides of the orchestra and by horizontal tubes disposed above the same orchestra. Moreover, using suitably placed transverse partitions within the vertical and horizontal tubes to form reverberation chambers, each having an open end, selected bands of frequencies in the spectrum of sound coming from the orchestra can be reinforced.

A stage having a reflecting shell and tubes disposed in accordance with the present invention is shown in FIG. 1, where shell 11 surrounds the sides, top and rear of stage 12. Vertical tubes 13 rest on stage 12 and are placed at the sides of the space to be occupied by an orchestra. Shell 11 is typical of one form of existing concert environment.

Horizontal tubes are placed above the area to be occupied by the orchestra and at a height such that mobility of the orchestra members is not hampered. As is evident from FIGS. 1 and 2, the horizontal tubes run transverse to the stage 12, that is, from side to side.

The diameter of the tubes, whether horizontal or vertical, may vary from about 1.5 feet up to about 4.0 feet. For dispersion of sound, the optimum diameter is about 2 feet, whereas for reinforcement of bass frequencies in the sound spectrum, a diameter of about 3 feet is optimum. However, dispersion and bass reinforcement are achieved over the entire specified range.

The need for reinforcement of low frequency tones arises from a number of factors, as described above. Where the auditorium is designed primarily for speech, the introduction of tubes above and around the orchestra in accordance with the present invention tends to rectify the imbalance caused by the construction of the auditorium. Also, where the performance of the orchestra is being recorded, the proper disposition of tubes in accordance with the invention compensates for the non-linear characteristic of the microphones. It should be noted that the reinforcement of the low tones persists for only about 250 microseconds, the rate of decay of each tone being more rapid when bass reinforcement is used.

The need for improved dispersion is particularly great in the case of outdoor performance. Under such conditions, the amount of reverberation is relatively low and sound intensity as heard by the audience is likewise low. Properly placed tubes help to confine the sound leaving the orchestra to the region occupied by the audience. Improved dispersion is particularly needed where the shape of the reflecting shell is essentially parabolic. With such a shell, movement of a player's head over a distance of a few inches can result in a sharp increase or decrease in the sound reaching the audience. The tubes of the present invention prevent such an effect.

Bass reinforcement results from placing a transverse partition in a tube as shown in FIG. 5. Chamber 15 is formed in tube 16 by means of partition 17. Since the chamber 15 has an open end 18, the chamber will reinforce a tone having a wave-length four times as great as the length of the chamber 15. Where it is desired to reinforce a band of frequencies ranging from say 37 cps to about 67 cps, the chambers should range in length from about 4 feet 5 inches to about 8 feet 9 inches, preferably in roughly equal steps. The frequency reinforced by a given chamber can be broadened into a band by cutting the open end of a chamber diagonally as shown at 19 in FIG. 6.

Where electronic amplification is desired, speakers may be installed in tubes as shown at 21 in FIG. 1. The removal of a panel from each tube in front of the speaker is necessary prior to installation of a speaker. In the embodiment shown in FIG. 1, the speakers are installed in tubes 22 in what are termed off-side tubes. However, speakers may be installed if desired in any of the horizontal tubes or the other vertical tubes which are essentially contiguous to the orchestra. Also, speakers should not be installed in tubes having a transverse partition to form a reverberation chamber because specific frequencies would then be too strongly reinforced.

As indicated above, the exteriors of the tubes aid in the dispersion of the orchestral sound. For maximum efficiency in this regard, tubes should be separated by no more than about 1/3 their diameter. Also, it is preferable that the tubes at either side of the orchestral space be aligned as shown in FIG. 2, roughly defining two divergent planes. The angle between the planes should be such as to include the entire audience space, but should not greatly exceed this value. Additional vertical tubes are placed at the rear of the orchestra with the particular objective of preventing anything resembling specular reflection from the rear of enclosure 11. The vertical tubes 22 are exterior to planes 23 and 24 defined by the vertical tubes at the sides of the orchestra. These tubes provide some reverberation using sound reflected from the audience space or from rear and side walls and ceiling if present. In some applications, vertical tubes only may be used; in such applications, horizontal tubes may be omitted because of lack of overhead space or because the vertical tubes alone give sufficient reinforcement and control of dispersion for the required purposes.

Horizontal tubes may be hung above the orchestral space in such relation as to define a plane passing somewhat above all individuals in the audience space. In a preferred arrangement, however, the horizontal tubes are disposed in groups of three as shown in FIG. 3. In each group of three, the middle tube makes contact with the tube in front and the tube to its rear. The rearward tubes in each group define a plane 31 which passes over the heads of all members of the audience. Such tubes are 26, 27, 29 and 30 in FIG. 3. However, the frontward tube in each group here exemplified by 25 and 28 is displaced upward by about half the diameter of the tubes. Surprisingly, this arrangement has been found to give superior dispersion of orchestral sound toward the audience, and particularly toward the upper part thereof.

Tubes which have been found to be satisfactory for the objectives of the present invention are manufactured by Sonoco Products of Hartsville, S. C., under the name of Sonotubes. The tubes are used as concrete forms, are cylindrical and can be had over a range of lengths. For convenience in shipping, tubes can be used in relatively short lengths and coupled together where needed.

The foregoing invention is especially useful in existing environments to substantially improve acoustical qualities for musical performances. The concepts of the invention are equally adaptable for permanent and temporary installation in new and existing structures.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made in the above construction without departing from the spirit and scope of the invention, it is intended that all matter contained in in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Claims

What is claimed is:

1. A system for improving the dispersion of sound toward an audience, said sound being produced by an orchestra on a stage, and for reinforcing low frequencies in the spectrum of said sound during the initial portion of reverberation, comprising vertical tubes on said stage at the sides and rear of said orchestra and horizontal tubes supported above said stage in a direction transverse to said stage and said orchestra, at least some of said vertical tubes having a chamber with one open end formed at the upper end of said tube by a transverse partition, and at least some of said horizontal tubes having a chamber with one open end formed at each end of said tube by transverse partitions, the lengths of said chambers in the different tubes varying in approximately equal steps from about 1/4 of the wave-length of the highest frequency to be reinforced to about 1/4 of the wave-length of the lowest frequency to be reinforced.

2. A system as defined in claim 1, wherein said tubes have a diameter of 1.5 to 4.0 feet.

3. A system as defined in claim 1, wherein an open end of at least one chamber in a tube, forms an angle with the axis of said tube sufficiently different from 90.degree. to cause said chamber to reinforce a band of frequencies.

4. A system as defined in claim 1, wherein said chambers range in length from about 4 feet 5 inches to about 8 feet 9 inches.

5. A system as defined in claim 1, wherein at least one electrically-driven speaker is mounted in a tube, a panel having been cut from the cylindrical wall of said tube to permit transmission of sound through the resultant opening.

6. A system as defined in claim 1, wherein said vertical tubes are about 1 foot apart.

7. A system as defined in claim 1, wherein said horizontal tubes lie close to a plane which is lower toward the rear of the stage and higher toward the front of the stage, the frontward extension of said plane passing above the highest portion of said audience.

8. A system as defined in claim 7, wherein said horizontal tubes are positioned in groups of three, the most forward tube in each group lying above said plane by about one-half the diameter of said tubes, the central tube of each group lying close to the other tubes of said group, said forward tube being thus positioned for the purpose of increasing the fraction of said sound dispersed toward upper portions of said audience.

9. A system as defined in claim 1, wherein said vertical tubes have lengths between 13 and 30 feet and said horizontal tubes have lengths between 35 and 75 feet.

10. A system as defined in claim 1, wherein the diameter of said tubes is about 2 feet, this diameter being optimum for dispersion of sound.

11. A system as defined in claim 1, wherein the diameter of said tubes is about 3 feet, this diameter being optimum for bass reinforcement.

12. A system as defined in claim 1, wherein said vertical tubes at either side of said orchestra define two planes, which when extended, include between them all individuals in said audience.

13. A system as defined in claim 1, wherein said vertical tubes at the rear of said orchestra are disposed in a plane.

14. A system as defined in claim 1, wherein the exterior surfaces of said vertical tubes are spaced, one from the other, by a distance no more than 1/3 the diameter of the tubes.

15. A system for improving the dispersion of sound toward an audience, said sound being produced by an orchestra on a stage, and for reinforcing low frequencies in the spectrum of said sound during the initial portion of reverberation, comprising vertical tubes on said stage at the sides and rear of said orchestra, at least some of said vertical tubes having a chamber with one open end formed at the upper end of said tube by a transverse partition, the lengths of said chambers in the different tubes varying in approximately equal steps from about 1/4 of the wave-length of the highest frequency to be reinforced to about 1/4 of the wave-length of the lowest frequency to be reinforced.