US1645329A - Sound amplifier - Google Patents

Description

Patented Uct. 11, 1927.

PATEN HELEN KANDERS, OF NEW YORK, N. Y.

SOUND AMPLIFIER.

Application led April 7, 1925.4 `Serial No.j2 1,316.

Marcli9, 1923, and Serial No. 690,374, ,filed February 4, 1924.

In loud speakers, such as horns and other amplifiers, conditions are present that nnpair the purity of directedtone,

The inherent or dominantnote of the horn is set into sympathetic vibrations each time this specific note appears 'in the varying pitch of the directed voice or other sound. The duration and strength of these sympathetic vibrations are increased with each recurrence, and the prolonged coexistence of disharmonies, viz: the horns own note against the changing pitch of the hvoice, 4causes the notorious clash and impurity of transmitted sound.

Another defect is that in horns of usual construction two different degrees of speed of vibrations are simultaneously existent, which also results in causing a sort of clash. The vibrations of the directed tone are in a forward direction and of uniform speed while the sympathetic vibrations in the amplifier slow down or are accelerated according to the number of times the dominant note of the material is roused.

I have demonstrated with several models, that the dominant note of the loud speaker can be eliminated and the voice transmitted with absolute purity. This is accomplished by providing a reflector' of conic section, (whether parabolic, elliptic, or of other' contour) connected with a sound conduit. The front part of this sound conduit is continued into the reflector so that the tone should strike the opposite wall of the reflector at a right angle or as near to that as possible, so as to prevent any part of the tone from passing out of the loud speaker' without being reflected.

As the distance from the mouth of' the sound conduit to the reflecting wall is negligible, the reflected tone issues co-incidentally and is of great purity as each successive T OFI-uca.. l

tone, due to the forcefulness of its reflection,

absorbs l and thereby eliminates eventual sympathetic vibrations in the material. Y

F or the same reasons there is also only one degree of vibrational speed.

Another feature of my deviceis that/it4 amplifles the transmitted sound in two ways f instead of one (by the length of the sound conduit and by reflection in the bell) and that therefore a comparatively small sized device can compete in tone volume with the largest horn. Other features and advantages of my invention will hereinafter appear.

ln the drawing: 4 ,Y ,y ,Figure lyis a side sectional elevation of my improved .loud speaker, and .Y

Fig.V 2 is a top plan view thereof. In said figures let 1 indicate a sound conduit, which is to convey sound waves that are produced by any well known means, as through the medium of a sound unit, 2.

This sound conduit isV shown as extended vertically for a portion of its length, gradually increasing in cross-sectional diameter, and is given a return bend 3 which terminates in an open mouth 4. This mouth 4 is shown as communicating with the reflector 5, at one side thereof, and at a point just adjacent the focus of said reflector. As shown, the mouth portion is entered through the side of the reflector 5, the forward portion 9 of said sound conduit protruding into the reflector interior to prevent the direct issuance of sound waves.

Since the longitudinal axis through the reflector4 is in a horizontal plane, in consequence the emitted sound from the mouth 4 of the horn is directed toward that side of the reflector opposite said mouth, and as Vthe mouth 4 is located just adjacent the focus of the reflector, full reflective value is achieved for the amplified sound. To aid in this effect the forward wall portion 9 of the sound conduit terminal extends into and lies part way across the interior area of the reflector, thereby preventing the direct issuance to the outside atmosphere of sound waves emitted from the sound conduit. the effect of forward wall portion 9 lying across a part of the reflector interior is to obstruct the direct issuance from the re.- flector of sound waves entering it through the sound conduit, it follows that said wall portion functions in the manner of a barrier or deflector, serving to direct the thus 0bstructed sound Waves to the reflector at a point opposite the entrance to the sound conduit adjacent the reliector focus, to thereby achieve the desired reflective values.

Variations Within the spirit and scope of my invention are equally comprehended by the foregoing disclosure.

I claim: Y

l. A sound amplifier comprising a res e'ctor of conic section and a sound conduit communicating with the reflector at oneside thereof in directional relation to the curved surfacek of saidrefle'ctor at its opposite side, and transversely across the focal laxis of said reflector. f Y

2. A Sound amplifier comprising a reflector of conic section kand a 'sound conduit communicating with the reflector at one side thereof, ata point justadja'cent to its focus, ind in directional relation lto the curved surface of said reflector at its opposite side, and transversely across the focal axis of said reflector.

3. A sound amplifier comprising a reiector of conic section and a sound conduit having means communicating with the reflector' at the side lthereof and at a point just adjacent its focus, the axis of said communieating means being perpendicular to the 5. An amplifier comprising a sound conrduit and a reflector of conic section, the

`mouth of the sound conduit communicating Withthe reflector through the side thereof, and the forward portion only vof the sound conduit projecting' part way into the reiector, in spaced relation tothe reflector surfaei'.

horn of the character described comprising'a body portion having a throat and a bell, said throatopening into said bell at a point forwardly of the inner end of the bell.

7. A semi-refiex horn comprising a body portion havingv a throat and bell, said throat opening into said bell at one side thereof and at a p'oint forwardly of the inner end thereof.

- Executed this 6th day of April, 1925.

HELEN KANDERS.

Images