3 305 043
ACOUSTIC COMMUNICATION DEVICE AND TOY
Charles E. Pfund, 16 Balcarres Road, West Newton,
Mass. 02165, and John W. Dawson, Winter St., Nor-
well, Mass. 02061
Filed Mar. 8,1965, Ser. No. 437,821
7 Claims. (CI. 181—27)
This invention relates generally to short-range communication devices and, more particularly, to an acoustic hand-held portable device for two-way communication. The device of this invention is particularly adapted to be carried by an individual and used both for transmission and reception while orienting the directive axis of the device toward a remote person who is equipped with a similar device thereby utilizing the directive gain of both devices for communication over substantial distances. By virtue of the simplicity and reliability of the device, it can be employed in a variety of applications and, in view of its economical construction, makes a novel toy for outdoor use.
Portable acoustic megaphones have been provided in the past for communication such as shown in the patent to Cunningham, 2,496,988, but such devices are limited in their gain and directivity and suffer from the unusually long aspect ratio of the device and difficulty in sighting for any given aperture of the exponential radiating horn. Parabolic acoustic signaling devices have also been provided in the prior art, such as shown in the patent to Maurer et al., No. 1,649,538, and while the paraboloids there employed are capable of significant gain, they do not provide a hand-held device which is capable of being optically oriented on a remote like-equipped station while being used for both transmission and reception.
It is, accordingly, the principal object of the present invention to provide a simple, compact, sturdy and light weight paraboloid acoustic communication device which is capable of being used for both transmitting and receiving and oriented by the user accurately toward a remote station during either the transmission or reception operation. These objects are achieved by a variety of constructions which utilize the acoustic gain of a parabolic reflector with the additional structure necessary for both acoustic transmission and reception being provided in a simple construction which is rugged and readily assembled from simple parts. The device in accordance with the invention provides a completely portable station which can be used for transmission and reception while aligning the acoustic directional axis of the paraboloid toward a remote station.
The features and objects of the invention will be understood from the following detailed description taken in conjunction with the accompanying drawings wherein:
FIG. 1 is a view in perspective of a local and remote station each consisting of an individual equipped with a device in accordance with the invention;
FIG. 2 is a top plan view partly in section showing one form of device suitable for both transmission and reception while sighting along the axis of the directivity pattern of the paraboloid;
FIG. 3 is a modified form of the invention employing a flexible acoustic conduit and an alternate form of optical sighting device;
FIG. 4 is a fragmentary view of a further alternate embodiment employing separate mouthpiece and earpiece devices with a novel switching element for changing from transmission mode to reception mode;
FIG. 5 is a sectional view taken along the line 5—5 of FIG. 4;
FIG. 6 is a fragmentary view of an alternate feed horn arrangement for paraboloid;
FIG. 7 is a plan view of a paraboloid with an acoustic tube terminating in a flared horn for energizing the paraboloid;
FIG. 8 is a similar view partly in section of another 5 alternative employing an exponentially tapered acoustic conduit terminated in a folded horn structure for energizing the paraboloid;
FIG. 9 is a view of another alternative employing an acoustic conduit and a convex reflector for illuminating j0 the paraboloid;
FIG. 10 is a top plan view of a modification employing a segment of a paraboloid having the paraboloidal surface offset with respect to the vertex of the paraboloid and requiring no acoustic feed conduit; 15 FIG. 11 is a top plan view of a paraboloid with a curved exponential horn feed adapted for transmission and reception with the operator standing at the edge of the dish instead of on the convex side thereof; and FIG. 12 shows a modification employing electronic 20 amplification for the reception mode.
Referring now to FIG. 1, the device of the invention in accordance with its simplest embodiment is seen to comprise a paraboloid 11 constructed of any suitable material, such as metal or plastic, and preferably re25 inforced by a curved rim 12 and provided with .an axial speaking tube 13 which extends from the convex side of the paraboloid to a point on the concave side of the paraboloid just short of the mathematical focus thereof. The distal end of the tube 13 has affixed thereto 30 by means of struts 14 an annular inverting bend in the form of a bowl 15 which acts to invert the direction of sound passing to and from the tube 13 thereby energizing the entire concave surface of the paraboloid 11. The effective acoustic continuity of the voice channel 35 even where physical discontinuity is necessary in order to reverse the direction of the sound progagation is important in devices such as herein disclosed where the physical size of the elements is generally not large in comparison to the wavelengths involved. In particular, 40 the optical analogy is not precise for defining the effect of secondary reflectors at the focus of the paraboloid. This is illustrated by the fact that in the acoustic device useful (although diminished) gain is achieved even with the bowl 15 not present whereas the presence of 43 a secondary reflector in an optical device is essential. The tube 13 is preferably of substantial inner diameter, of the order of one inch or more, and is mounted at the vertex of the paraboloid 11 by means of a reinforcing collar 16 of any suitable construction. On the concave side three radial supporting struts 17 may be employed to give the tube 13 structural rigidity in alignment with the acoustic directive axis 10 of the paraboloid 11. On one of the struts 17 a bead 18 may be secured 5_ positioned for alignment with a small hole 19 in the surface of the paraboloid 11 thereby providing an optical sight which is parallel with the direction of the axis of the paraboloid 11.
The entire structure as thus described may be readily 60 held and used as indicated for both transmission by speaking into the open end of the tube 13 or by turning the head to position the ear at the open end of the tube 13 for listening. In the listening mode the directivity can be maintained at the aligned position established during 65 transmission and the detection of incoming sound can be maximized due to the directive pattern of the paraboloid to maintain the alignment by means of the sensitivity of the ear in hearing the decrease in sound amplitude that