US1829899A - Apparatus for the rectification and amplification of sound waves - Google Patents

Description

' H. N. JAMES, 1,829,399 APPARATUS .FOR 'THE RECTIFIGATION AND AMPLIFICATION OF SOUND WAVES Filed June 2'7, 1930 2 Sheets-Sheet 1 Nov. 3, 1 931.

Illlill Patented Nov. 3, 19 31 PATENT OFFICE HENRY NEWTON JAMES, OE CHICAGO, ILLINOIS APPARATUS FOR THE RECTIFICATION AND AMPLIFICATION 01 SOUND WAVES Application filed June 27,

This invention relates to improvements in apparatus for the rectification and amplification of sound waves, and more particularly to a device to be used in coni'unction with any instrument for mechanica ly or electrically reproducing sound, such as the loud speaker unit of a radio receiving set or phonograph;

The object of the invention is to provide an instrument or device, having as its primary function the rectifying and clarifying of reproduced sound waves, and thus eliminating the discordant and distorted tones due to faulty re roduction and amplification.

A further ob ect of the invention is to provide an apparatus especially designed to be used in theaters and auditoriums in which sound is reproduced, as for instance, from records and in synchrony with motion pictures by an electro-magnetic reproducer or dynamic loud speaker, and as such is intended to rectify and clarify the sound as it is projected from the reproducer and then amplifying it to the proper volume for clear reception by the audience.

While the device embodying my invention is in part an amplifier of sound waves, it is not an amplifying horn as its general shape may indicate but, as will presently be seen, is a vibratory shell into which the reproduced sound waves are projected and through the agency of wires tuned to a true harmonic pitch scale extending throughout the full range of sound vibration frequencies, the true tone vibrations are again reproduced by sympathetic vibration of the wires and am lified by the vibratory walls of the shell, w ile the discordant sounds to which the wires do not respond are filtered out and thus eliminated.

A preferred embodiment of my invention is disclosed in the accompanying drawings in which:

Figure 1 is a general view in side elevation of the device. I

Figure 2 is a view in front elevation.

Figure 3 is a view in vertical section longitudinally of the device as taken on line 3-3 of Figure 2. I r

Figure ,4 is an enlarged detail view in ver- 1830. Serial No. 464,142.

tical section through the sound chamber, as taken on line H of Figure 3.

Fi ure 5 is an enlarged detail view showing t e manner in WhlCll the strings of-the sound chamber are tuned.

Figure 6 is a detail view in section through a corner of the sound shell, showing the construction and method of mounting the tuned wires, and

Figure 7 is an enlarged detail view in section of fragments of the shell and the screen supporting the external groups of wires.

Referring to the device in its general aspect, the same consists of a box-like sound duct 1, square in cross-section and from 3 to '5 feet in length and say one foot to two feet square in its internal dimensions. This duct 1 is open at both ends and at one end it connects with and opens into the apex of a pyramidal-shaped shell 2, that is, a four-sided hollow casing diverging from a framed opening connected with the front end of the sound duct 1 to a large framed opening about six feet square.

The device rests in horizontal position on the floor with one of the edges of the shell 2 in contact therewith, thus elevating the sound duct 1 to a height of, say, 2 or 3 feet above the floor. Supporting the rear end of the sound duct is an upright member 3, and extending rearwardly therefrom and below the opening to the duct is a shelf 4 on which rests the sound reproducer 5 which may be assumed to be an electro-magnetic loud speaker such as would be used in reproducing sound from records or a radio receiver. The cone 5a of the loud speaker 5 is directed into the open end of the sound duct and registers with an opening 3a formed in the upright 3, so that the sound waves emanating from the reproducer are delivered axially to said duct. By preference the reproducer is enclosed within a removable housing or hood 6 supported upon the shelf, this hood being a boxlike enclosure of any suitable construction having its walls lined with a heavy nap fabric such as velour. The purpose of this hood is to absorb all sound vibrations emanating from the reproducer which are'not desired to be transmitted into the sound chamber or passage within the duct.

- The sound duct 1 considered as a separate unit of the device, is preferably constructed of wood, with walls of, say, one inch in thickness, or at least of sufficient thickness to resist vibration under the influence of the sound waves. Moreover, the duct is preferably constructed in two sections, that is, a main section 1a of greater length adjacent the sound receiving end, and a short section 16 ad acent the shell 2.

These two sections are joined end to end by abutting end frames 7 7, there being similar frames at the extremities of the duct, and which, as will be presently seen, serve as the supports for banks or series of vertical metal strings which extend across the sound chamber at intervals throughout its length. The sound duct is preferably made in sections for convenience in adapting the device to auditoriums of different sizes, that is to say, a relatively small auditorium will permit of a shorter sound duct and hence the, shorter section can be removed without necessitating a complete reconstruction of this portion of the apparatus. However, for the purpose of this disclosure, the sound duct may be considered as a single section.

In the top wall of the sound duct and at equal and predetermined intervals along a median line are a series of holes 8, say, of

inch in diameter, these holes being fitted with removable stops or plugs 9. There are shown eight stops in the larger section Ia and two in the shorter section 16 of the sound duct. Also in the bottom walls of the duct is a vent hole 10 also provided with a stop or plug 11. It may be stated at this point that these holes are made use of in adjusting the apparatus to the particular auditorium in which it has been installed, in order to secure the best results. Thus by removing a certain stop or stops from the holes 8, together with the stop from the vent hole 10, the volume of sound passing through the chamber is diminished until it meets the volume requirements of the auditorium as determined by its capacity and acoustic conditions.

Adjacent each of the frame members 7 of the sound duct 1 are mounted sets or groups of parallel tuned metal strings or wlres 12 arranged to extend vertically through the interior of the sound chamber (Figures 3 and 4). The strings of each group are strung between bars 14: and 15 extendin transversely across the top and bottom wal s of the duct and abutting against the frames 7, said strings pbassing through small bores in the top and ottom walls of the duct and thence through or into registering bores 14a and 15a in the bars 14, 15 respectively. Thus the lower ends of the strings are fixed to screws 15?) anchored in the under side of the bottom bars 15, while the upper ends of the strings are attached to tuning pins 16 similar to those used on stringed instruments of the mandoline type. As shown in Figure 5, each string is coiled upon a tuning pin consisting of a shaft 17 extending transversely of the bore 14a in the bar 14, which is rotated by a worm wheel 17a on the shaft and a worm 18 on a tuning spindle 18a supported in a bracket 19 secured to the' face of the bar 14. As shown in Figure 3, there are four groups of eight (8) strings each, between the ends of the duct, although the number of groups, the

a definite note in the scale, responds to and vibrates in sympathy with a sound wave of the same frequency entering the sound chamber.

Thus, one group of strings may include the highest pitched notes, another the next lower, and so on until the full ran e is covered between the higher frequency limits mentioned, the maximum of 8192 cycles per second being recognized as the limit of audible reception.

Referring now to the vibrator shell 2, the same consists of a substantial frame work including a small square frame 20 which surrounds the central opening from the sound duct and abuts the end frame 7 thereof, diverging corner frame members 21 of angle section, and a large square frame 22 surrounding the open end. These frame members joined together, form a rigid skeleton frame of pyramid shape, and included therebetween are four thin walls or vibratory panels 23, which surround the four sides of the frame. These vibratory panels may be made of any suitable material such as wood or a composite material having the requisite resonant qualities of a vibratory sounding board. As shown in Figure 6 these panels 23 cut to shape, are fitted at their edges into the frames 20 and 22, and edges of the frame members 21, thus forming angularly disposed divergent walls, each forming a separate vibratory unit.

The shell is preferably braced and reinforced externally, but since these are details which may be modified without affecting the function of the shell, they need not be elaborated upon.

Extending transversely of each of these vibratory panels and within the shell are other series or groups of tuned wires 24 arranged in parallel relation and anchored at their ends to the corner frame members 21,

that is, the wires of each group are fixed at one end to suitable pins 25 anchored in one of the frame members and secured to a corresponding row of tuning pins 26 on the frame members on the opposite side as shown in Figure 6, these tuning pins being similar to those used in piano construction. Narrow bars 27 in which a bridge strip 28 is inserted, are applied along the edges of the frame members 21 adjacent the rows of pins 25 and 26, so that the wires are spaceda uniform distance from the surfaces of the panels 23, and their length is defined.

Thus each frame member supports rows of fixed and tuning pins for the groups of tuned wires on either side thereof, t ese wires being approximately one hundred and fifty in number, that is, about forty in each grou and ranging from one foot to, say, five an one-half feet in length. Moreover, the strings surrounding the interior of the shell are heavier than those within the sound chamber, and are tuned to vibrate at frequencies between 2900 and 500. cycles per second, the shorter strings being manifestly tuned to the higher frequenc pitches. Over the opening or mout of the shell 2 is a screen of tuned wires 29, which for structural reasons are preferably supported upon a separate square frame of about the same size as the open end of the shell 2, and consisting of two heavy beam-like members 30 which support the. ends of the wires, and a plurality of transverse members in the form of tubular columns 31 extending between the ends of the beams. The beams 30, 30 extend horizontally in line with the top and bottom of the shell, and are fastened to the outer frame 22 of the shell 2 by suitable attaching devices such as lag screws 32 and spacing,

sleeves 32a, (Figure 7). The strings 29 are all of the same length and preferably divided,

into two groups on opposite sides of the beams, the same arrangement of anchor pins 33 and tuning pins 34 being carried by the beams for supporting the ends-of the wires.

There are about 160 wires in this screen which extend in a double row entirely across the opening to the shell, and bein relatively heavy wires and under considera le tension when tuned, demand not only a separate frame, but their division into groups on opposite sides, in order to equalize the stresses on the, frame and prevent its distortion.

Moreover, the frame supporting the external groups of strings is made removable so that access may be had to the internal groups of strings for tuning. And finally as in the case of the other groups of wires, these strings are tuned to the physical pitch scale, but being relatively heavier and longer, embrace the lower frequencies of sound wave vibrations, say, from 26 to 500 cycles per second.

Considering now the several groups of tuned strings or wires as a whole, it will be seen that they are divided into three series,

namely, those in the sound chamber of the the strings are all tuned to a different pitch,

although two or more strings may be tuned to the same pitch. Moreover, the tuning is in accordance with the physical pitch scale based on middle C, with a frequency of 256 cycles per second, and ran ing above and below that note throughout tl ie. range of audible frequencies.

Now, considering sound entering the sound chamber from the reproducer 5 as waves or v bratory-disturbances of the atmos here of different frequencies, it follows t at the string or strings having the same frequency Wlll be set in motion and vibrate in sympathy therewith, producing the same note. Thus if the sound reproduced, whether s eech or music, is harmonious, it will again e reproduced 1n its passage through the sound chamber and shell, not only in pure tones from the vibration of the strings tuned to ing and reproduction of sound by mechanical agencies is not altogether perfect, some of the tones being distorted, and other tones, notably those in the lower frequency range, being suppressed. In addition, inharmonious overtones and mechanical noises are created in the course of reproduction and amplification, which interfere greatly with clear and harmonious reception. In passing through the apparatus, these undesirable notes, overtones and noises are modified and suppressed to a great extent, whereas the true and harmonious notes are reproduced, amplified and brought up to their proper volume so that the result is a harmonious bal anced whole in harmonics and chromatics.

The true sense of tone reproduction as accomplished by the use of'the apparatus is erhaps rendered more understandable by hearing in mind that the sound emanating from the reproducer is not the same sound which ultimately reaches the ear. In fact, the sound projected into the chamber of the apparatus is in reality only waves which set in vibration the tuned strings pitched to frequencies of the true physical scale so that the source of the audible sound is the strings and not the reproducer. Consequently no sound or note which is not true or harmonious, is created and amplified for audible reception by the apparatus. Thus it will be seen that the apparatus is not a musical instrument on the one hand, or an amplifying horn on the other, but rather a mechanical device which receives a vast assortment of sound Waves, and functions to rectify those that are slightly off tone, to suppress and modify those that are discordant or foreign, and finally to amplify and project the true and harmonious tones with clarity, mellowness and purity.

Having set forth a preferred embodiment of my invention, I claim:

1. In an apparatus of the character described, the combination with a sound reproducer of an elongated sound chamber of uniform dimensions adapted to receive the sound waves from said reproducer at one end, and having a multiplicity of strings strung transversely thereof and tuned to a predetermined pitch scale, and an amplifying shell having vibratory'walls communieating with the other end of said chamber.

2. In an apparatus of the character described. the combination with a sound reproducer of an elongated sound chamber adapted to receive the sound waves from said reproducer at one end, and having a multiplicity of strings strung transverselv thereof and tuned to a predetermined pitch scale, and a reflecting shell having .vibratory divergent walls communicating with the other end of said chamber.

3. In an apparatus of the character described, the combination with a sound reproducer of an elongated sound chamber open at each end and adapted to receive sound waves from said reproducer, a shell communicating with said chamber and having divergent vibratory walls and a plurality of tuned vibrating elements within said chamber and shell and adapted to be set in vibration by the passage of sound waves therethrough.

l. In an apparatus of the character described, the combination with a sound reproducer of an elongated sound duct of uniform internal dimensions adapted to receive the sound waves from said reproducer at one end and open at its opposite end, said duct having a series of longitudinally spaced holes through the wall thereof, and removable stops for closing said holes communicating with said sound chamber.

5. In an apparatus of the character described, the combination with a sound reproducer of an open ended elongated sound duct of uniform internal dimension, having a series of longitudinally spaced holes through the wall thereof, stops normally closing said holes, and a group of strings extending transversely of said duct and adapted to be tuned to a predetermined pitch scale.

6. In an apparatus of the character described, the combination with a sound repro-' ducer of an elongated sound chamber of uniform internal dimensions, a series of longiscribed, the combination with a sound re'producer of an elongated sound chamber of uniform internal dimension open at one end, groups of tuned strings extending transversely of said chamber, a sound reflecting shell arranged symmetrically about the open end of said chamber, and groups of tuned strings mounted on the inner surface of said shell.

8. In an apparatus of the character described, the combination with a sound reproducer of an elongated sound chamber of uniform internal dimension, groups of tuned strings extending transversely of said chamber and arranged in spaced relation throughout the length thereof, a reflecting shell arranged symmetrically about the open end of said chamber, groups of tuned strings mounted adjacent the inner surface of said shell and tuned strings extending across the large open end of said shell.

9. In an apparatus of the character described, the combination with a sound reproducer of a sound duct having one end open to receive the sound vibration from said reproducer, a sound reflecting shell havin vibratory walls diverging from a centra opening communicating with the other end of said duct, and a frame surrounding its outer end, and a multiplicity of tuned strings extending across said frame.

10. In an apparatus of the character described, the combination with a sound reproducer of a sound duct having one end open to receive the sound vibration from said reproducer, groups of tuned strings extending transversely of said duct, a sound reflecting shell having vibrator, walls diverging from a central opening communicating with the other end of said duct, and a screen consisting of a multiplicity of tuned strin s extending over the open end of said shel 11. In an apparatus of the character described, the combination with a sound reproducer of a sound duct having one end open to receive the sound vibration from said reproducer, a sound reflecting shell having vibratory walls diverging from a central opening communicating with the other end of said duct, and a frame surrounding the outer end of said shell supporting a multiplicity of tuned strings.

12. In an apparatus of the character described, the combination with a sound reproducer of a sound duct having one end open to receive the sound vibration from said reproducer, groups of tuned strings extending transversely of said duct, a sound June, 1930.

reflecting shell having vibratory walls diverging from a central openin communicat ing with the other end of sai duct, groups of tuned strings extending transversely of the inner faces of said walls, and a frame mounted in front of said shell and sup orting a multiplicity of parallel tuned strings.

13. In an apparatus of the character described, the combination of a sound duct 9. sound reflecting shell communicating with one end of said duct, a sound reproducer mounted at the other end of said duct, and a sound absorbing hood surrounding said reproducer.

14. In an apparatus of the character described, the combination of an elongated duct having non-virbratory walls, a sound reflecting shell having a central opening communicating with one end of said duct and vibratory diverging walls, a support at the opposite end of said duct, a sound reproducer mounted on said support, and a sound absorbing hood enclosing said reproducer.

15. In an apparatus of the character described, the combination of a sound duct adapted to receive sound waves at one end, a sound amplifying shell communicating with the opposite end of said duct, a series of tuned strings mounted within said sound duct, and means for varying the volume of the sound produced to the size of the auditorium in which the apparatus is located.

16. In an apparatus of the character de scribed, the combination of a sound duct adapted to receive sound waves at one end, a sound amplifying shell communicating with the opposite end of said duct, and aplurality of groups of tuned strings extending across said sound duct and spaced apart longitudinally thereof.

17. In an apparatus of the character described, the combination of a sound duct adapted to receive sound waves at one end, a

sound am lifying shell communicating with the opposite end of said duct, and a plurality of groups of tuned strings extending across said sound duct and spaced apart longitudinally thereof, and means in said sound duct for varying the volume of the sound produced to the size of the auditorium in which the apparatus is located.

18. In an apparatus of the character described, the combination of a sound duct adapted to receive sound waves at one end, a sound amplifying shell communicating with the opposite end of said duct, and groups of I,

strings extending transversel of said sound duct and across the mouth 0 said shell and capable of being tuned to predetermined scales.

Signed at Chicago, 111., this 24th day of HENRY NEWTON JAMES.

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