US2007128A - Sound-box construction - Google Patents

Description

y 1935- J. M, LUCARELLE 2,007,128

SOUND BOX CONSTRUCTION Filed Aug. 8, 1931 v v v I 2 //5 6 2 ATTORNEYS.

Patented July 2, 1935. I

J UNITED .sTAres PATENT OFFICE 5 Claims. (01. 274-27) I'his invention relates to sound-boxes and more particularly sound-boxes suchas are employed for recordingsounds upon a; cylindrical wax recv rd blank.

One of the defects inherent in such soundboxes as have been heretofore used for the re.

to sound'waves of relatively lowfrequency and weakly or inefficiently to sound waves of relatively high frequency. When a record made under these conditions is reproduced, the sounds produced seem to be lower in tone than the sounds recorded, and have lost many of their quality or personality characteristics. ,A well-known example of this defect is the reproduction of a wax cylinder record of the human voice. Through the loss of many of thehigher wave frequencies and apparent exaggeration of the sound waves of low frequency, the record when reproduced sounds unnatural and the voice is often. unrecognizable. Also the general audible effect is poor, and the reproductionunsatisfactory, often being so dull and muffled as to be almostunintelligible. This is easily understood when' it is remembered what a large part the high frequency overtones have to play in determining the characteristic qualities of the voice. I i It is believed that the cause of the loss of the higher wave frequencies in recording is due to the fact that the energy of speech resides principally in the frequencies below 1000 cycles per second and that articulationand intelligibility reside mostly in the higher frequency sounds, those above 1000 cycles per second. Consequently the diaphragm of the sound-box, responding with greater amplitude to the low frequency sounds, produces a record in which these sounds predominate.

Another objectionable feature of the usual type of sound-box is the tendency of the diaphragm to blast when a strong or loud voice'is recorded. vThis seems to be due to the fact that the force of the loud voice or musical note, as the case may be, is greater than the responsive capacity of the diaphragm. A fluttering of the diaphragm results which in a recorder produces breaks in What should be a smoothly continuous hill-anddale track formed upon the record-cylinder surface. When thereproducing stylus, in reproducing the record, travelsover this portion thereof, it produces a harsh and foreign noise, in addition to a distorted reproduction of the original sound. Not only is the sound or note more or less imperfectly reproducedbut the sound occasioned by the concussion of the sapphire against the abrupt edges of the breaks in the record track, is concurrent therewith.

ume and this may best be attained by the use of comparatively thin diaphragms, which, unfortunately, are more susceptible tobla-st than those of greater substance. V

; It is an object of the present invention to pro- 10 vide a sound-box capable of producing a record substantially free from the evils of blasting, even when sound waves of relatively great amplitude are impressed upon the diaphragm. Another object is to provide means adapted to pre-' 15 vent blasting? even when diaphragms of exceptional thinness are mounted in the sound-box.

Another object is to provide a device of the nature described capable of recording and reproduc-v ing in a highly natural manner. Another object 20 is to increase the voice or tonal range of a sound- "The invention accordingly consists in the fea- 35 tures of construction, combinations of elements,

and ai'rangementsof parts as will be exemplified in the structure to be hereinafter described and the scope of the application of, which will be indicated in the following claims. I

In the accompanying drawing in which is shown one of the various possible embodiments of my invention: V r

Fig. 1 is a side elevation of a sound-box of a well-known type, showing a portion of the tonearm;

Fig. 2 is an end elevation'thereof;

Fig. 3 is a section taken on line 33 of Fig. 4;

Fig. 4 is a section taken on line 4'4 of Fig. 3, 50 and Fig. 5 is a perspective view of a leak-oif, damping and sound wave spreading device, employed .in my sound-box construction.

, Similar reference characters refer to similar 55 It is usually desirable to get considerable vol- :5

parts throughout the various views of the drawing.

The sound-box shown in the present embodiment of my invention involves the use of a sound wave bafile and leak-off. Referring to the drawing, the sound-box structure comprises a tonearm or tube I closed at its end, as by the wall 2 and which is provided with a downwardly turned flange 3 surrounding a circular opening 4. The pan or sound-box head comprises a shallow inverted dishlike member 5 having circumferen tial walls 6. The circular edge 1 of an opening formed in the center of the pan is seated in and secured to the tone-tube by turning the flange 3 over said edge, as at 8, as shown in my present construction, although it will be understood that the tone-arm and pan may be formed integrally. Such an integral construction is shown in the patent to Bodine et al., No. 1,606,744, to which reference is made for a description of the manner in which a combined recorder and reproducer may be mounted and an explanation of its mode of operation as applied to a commercial dictating machine.

The pan is further supported by a boss 9 formed on the tone-arm l to which the pan is attached by means of a screw ID. A diaphragm II is suitably mounted in the sound head, as by means of gaskets l2-|3, which in the present construction are held in place by means of a fillet I4 of plastic material such as beeswax. The diaphragm is preferably made of mica, perforated at its center for the passage of a small screw l5, which is threaded into and makes fast to the diaphragm a stylus or point holder l6. Holder I6 is further supported upon the diaphragm by means of an arm I! having an offset portion l8, which, in assembling, is passed through a perforation in the diaphragm, as at I9. The stylus holder is of familiar form and provides a seat for a recording stylus 20 and a reproducing stylus 2| either of which may be brought into operative engagement with a record-cylinder, by means shown and described in the Bodine patent referred to above.

No novelty is claimed for the features thus far described.

The upper wall of the tone-arm is perforated as at 22, by punching or otherwise, at a point directly opposite the center of the opening 4, to receive a hollow funnel-like plug 23 terminating in an enlarged conical end 24 which extends downwardly through the opening 4 into close proximity to the diaphragm. The plug may be swaged tightly within the opening 22, or made fast therein in any other suitable manner. The object of this plug member is to prevent the impinging of sound waves directly at the center of the diaphragm and to cause them to strike an annular portion of the diaphragm adjacent the periphery thereof, and has other objects as will presently appear.

The result of this limitation of impact appears to be twofold. In the first place it serves to prevent blasting and thus ensures the tracing of a smoothly continuous track upon a record-cylinder during recording. This result permits the use of thinner diaphragms, from which it follows that a tone of a certain intensity will produce sound wave tracks upon the record of greater amplitude; and greater volume is attained when the record is reproduced.

And secondly, it has been found that the deflection of the sound waves accomplished by the conical plug tones down the effect produced upon the diaphragm by vibrations of lower frequency and permits it to respond more accurately to vibrations of higher frequency, thus enabling a record to be made of these higher frequency waves and a consequent improvement of the quality of the tone and the attainment of a higher pitch when the record is reproduced.

Many tests of the standard type of recorder-reproducer, in which the conical plug is omitted, establishes the fact that it is naturally responsive to sounds up to 2500 cycles per second and,

with increasing weakness, to sounds up to 4-300 cycles per second. On the other hand, tests with sound-boxes m which the conical plug was used showed that they were naturally responsive to sounds of 3500 cycles per second and, with increasing weakness, to sounds up to 500% cycles per second. As would be expected, this resulted in more natural recording and reproducing, in that there were saved many overtones and other characteristics which determine timbre or voice personality. This result is believed to be in part due to the damping effect of the air cushion established above the diaphragm and within the interior of the funnel-shaped plug, which aids in preventing blasting and makes the diaphragm more responsive to sound waves of higher frequency.

But a further improvement in the action of the device when used as a recorder has been effected by the provision of a leak-off channel 26 in the plug 23. This channel connects with the interior of the sound-box at a point just above the diaphragm through the conical end of the plug. The upper end of the channel is connected with the atmosphere exteriorly of the sound-box by means of plural passages 28. A cap 29 fits snugly over the upper end of plug 23 and has openings 30 in its cylindrical wall, which may be made to register wholly or to any desired partial extent with the openings 28. Although I have shown means for adjusting the amount of leak-off, beneficial results. may be attained by the use of a leak-off of predetermined and invariable capacity, and under some conditions such an arrangement is preferable.

The chief benefit derived from the leak-oil seems to be that by its use the recorder is able to handle with substantially equal efficiency vibrations covering a wide range of intensity. The excess energy of a loud voice is drained off to the surrounding atmosphere so that the diaphragm is not put under an overstrain. This prevents rattle and blast of the diaphragm and ensures the production of a good record.

Waves of low frequency which have a larger share of the energy of speech than those of high frequency, are leaked off to a greater extent than are the latter, and thus the leak-off passage aids the baffling and damping effects of the plug in effecting the recording of more of the higher overtones or partials of the voice and so enhance the quality of reproduction.

It will be seen that there is provided a construction of an essentially practical nature in which the several objects of this invention are attained.

As many possible embodiments may be made of the above invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense. I

I claim as my invention: I

1. In a dictating machine, in combination. a

sound-box, a disk-shaped diaphragm in said sound-box supporting a stylus, a sound-conduit connectingwith the interior of. said sound-box through a circular opening which with respect to said diaphragm is of relatively small diameter, and a substantially funnel-shaped member mounted with its open base directed toward said diaphragm and its body extending through said opening into said sound-conduit, the diameter of said member in the plane of said opening being substantially less than the diameter of said opening.

2. In a dictation recording machine, a soundbox, a diaphragm in said sound-box, a tone-tube connecting with the interior of said sound-box through a circular opening, a conical plug mounted in said opening with its base open and directed toward said diaphragm, and a leak-on passage in said plug connecting the interior of said soundbox with the atmosphere.

3. In a dictation recording and reproducing machine, a sound-box, a diaphragm in said soundbox supporting a recording and a reproducing stylus, a 'tone-tube connecting with the interior of said sound-box through a circular opening, a hollow conical plug mounted in said opening with its'base directed toward said diaphragm, and a leak-01f passage in said plug connecting the interior of said sound-box with the atmosphere.

4. In a dictation recording and reproducing machine, a sound-box, a diaphragm in said soundbox supporting a recording and reproducing stylus, a tone-tube connecting with the interior of said sound-box through a circular opening, a conical plug mounted in said opening with its base directed toward said diaphragm'a leak-ofi passage in said plug connecting the interior of said sound-box with the atmosphere, and means for wholly or partially obstructing said passage.

5. In a dictating machine, in combination, a sound-box, a disk-shaped diaphragm in said sound-box supporting a stylus, a sound-conduit connecting with the interior of said sound-box through a circular opening which with respect to said diaphragm is of relatively small diameter, a substantially funnel-shaped member mounted with its open base directed toward said diaphragm and its body extending through said opening into said sound-conduit, and a leak-off passage'in said member connecting the interior of said sound-box with the atmosphere.

JOSEPH M. LUCARELLE,

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