Hinged acoustical voice tube
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to acoustical communications headsets and, in particular, to an adjustable, light-weight voice tube for such a headset. 
     2. Discussion of the Prior Art 
     Prior art acoustical communication headsets incorporate an acoustical tube or &#34;voice tube&#34; to carry sound to the microphone in the housing. In all such devices, some accommodation must be made so that the end of the tube is near the user&#39;s mouth, regardless of differences in anatomy between users. Typically, this accommodation involves the use of a sliding, trombone-like attachment. One such attachment being described in U.S. Pat. No. 3,548,118 issued to Hutchings. Other examples can be found in U.S. Pat. Nos. 3,993,879, 4,090,042, and 4,118,606 issued to Larkin. 
     A major problem with trombone-type voice tubes is that they produce a change in voice level when adjusted, much like the change in sound achieved with the slide in the musical instrument. These changes in voice level are unsuitable for oral communication, particularly in those cases where the sound must be transmitted over standardized equipment such as telephone lines. 
     SUMMARY OF THE INVENTION AND OBJECTS 
     It is a general object of the present invention to provide a lightweight acoustical voice tube which can be used with a communication headset. 
     It is another object of the present invention to provide an acoustical voice tube which is adjustable so as to accommodate the differences in anatomy of the voice tube user. 
     It is another object of the present invention to provide an acoustical voice tube where adjustments made to accommodate the user do not impact sound quality or sound level. 
     In general, the above and other objects of the invention are achieved by an acoustical voice tube for use with communication equipment which comprises a hollow, acoustical upper piece having an upper end for detachable coupling with the communication equipment and a lower end, and a lower piece having a lower end adapted for receiving sound and an upper end adapted to accommodate the lower end of the upper piece so as to create a hinged connection between the upper and lower pieces. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a pictorial view illustrating an acoustical voice tube in accordance with the present invention as it would be placed in relation to a user of communication equipment. 
     FIG. 2A is an enlarged underside view illustrating the acoustical voice tube showing the hinged connection between the upper and lower pieces. 
     FIG. 2B is an enlarged side view of the acoustical voice tube showing the hinged connection between the upper and lower pieces as well as the sound filter. 
     FIG. 2C is an enlarged view of the sound filter showing the filter screen. 
     FIG. 3 is the transmit frequency response template of a prior art trombone voice tube in various positions of adjustment. 
     FIG. 4 is the transmit frequency response template of the present invention in various positions of adjustment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a user (10) is shown with an acoustical voice tube (11) placed in proper relation to the user&#39;s mouth and ear, for use with communication equipment (not shown). The voice tube is comprised of a hollow upper piece (12) and a hollow lower piece (13) in hinged connection (14). The hinged connection allows for flexure of 40° (arrows) without undue effort and yet is tight enough to maintain a set position after adjustment. 
     Referring to FIGS. 2A-2C, the upper piece (12) consists of an upper end (15) and a lower end (16). Detachable air-tight coupling and pivotal air-tight rotation of the upper piece (12) in relation to the communication equipment is provided by a rounded notch (17). The lower end (16) of the upper piece (12) has two convex protrusions (18A and 18B), thickened side walls (19) and a rounded, knuckled tip (20). 
     The lower piece (13) has a lower end (21) and an upper end (22). The lower end (21) of the lower piece (13) is adapted for receiving sound, having an end filter (23) to serve as an acoustical resistor. The end filter dampens acoustical resonances by virtue of a filter screen (24) secured by a filter housing (25). The upper end (22) of the lower piece (13) has partially cylindrical side walls (26A and 26B) with a radial axis in a perpendicular relationship to the hollow acoustical upper piece (12). The cylindrical sidewalls (26A and 26B) have bores (27) in a parallel relationship to the radial axis and aligned for air-tight coupling with the two convex protrusions (18A and 18B) of the lower end (16) of the upper piece (12) creating a hinged connection (14) between the lower piece (13) and upper piece (12). 
     In the preferred embodiment, the length of the upper piece (12) is less than one-third the length of the lower piece (13) and the lower piece (13) is curved. The diameter of the hollow, acoustical upper piece (12) and the diameter of the hollow, acoustical lower piece (13) are the same and are less than one-eight of one inch. The lower piece (13) and upper piece (12) are made of clear, impact resistant plastic material. 
     Referring now to FIG. 3, the loss of sound level upon adjusting the position of prior art trombone type voice tubes is demonstrated on a frequency response graph. The y axis measures the relative response in decibels (dB) while the x axis measures the transmit frequency in hertz (Hz). The line designated &#34;green&#34; is the reference template. The line designated &#34;black&#34; shows the transmit frequency response of the trombone type voice tube when it is adjusted so that the lower tube is fully extended. The line designated &#34;brown&#34; shows the transmit frequency response of the trombone type voice tube when it is adjusted so that the lower tube is all the way in. It is clear that the response at any particular frequency is dependent on the adjusted position of the trombone type voice tube. 
     Referring now to FIG. 4, the frequency response for the hinged voice tube of the present invention is shown to be independent of the adjusted position of the tube. Again, the y axis measures the relative response in decibels (dB) and the x axis measures the transmit frequency in hertz (Hz). The acoustical voice tube was evaluated where the hinged connection (14) was positioned so that the angle created by the upper piece (12) and lower piece (13) was 0°, 15° down, and 15° up. It is clear that the response at any particular frequency is exactly the same regardless of the adjusted position of the acoustical voice tube. Flexure of 30° occurs without change in the frequency response or sound pressure level, i.e. sound level. In combination with the pivotal rotation of the upper piece, the acoustical hinged connection permits voice or sound tube positioning over a large area without changing the sound characteristics.