GB101698A - Improvements in Methods and Apparatus for Transmitting and Receiving Sound Waves through the Ground. - Google Patents

Abstract

101,698. Fessenden, R. A. Oct. 7, 1915, [Convention date]. Audible signals transmitted through the ground; locating sounds.-In electrical apparatus for receiving and transmitting sound waves through the ground the vibrations are transmitted between the earth and electrical apparatus through a separate liquid or solid conductor arranged to produce a difference in phase between different parts of the apparatus. In one form a device 11, such as an oscillator of the kind described in Specification 18765/13, sensitive to or capable of producing vibrations is submersed in water, oil, or other liquid 23 below the surface 13 of the ground. A two-way switch 15 is provided whereby the device 11 may be placed in circuit with an alternating-current generator 19 and key 21 for transmitting, or with a telephone receiver 17 for receiving signals. By replacing the generator 19 and key 21 by a storage battery and telephone transmitter, the apparatus may be used for telephoning. In a modified form, the oscillator, instead of being submersed, is mounted on an horizontal wire or rod supported at its ends by inclined rods screwed or driven into the ground. This arrangement is directive, receiving and transmitting most readily along the line of the supports. The device shown in Fig. 4 for ascertaining the direction of a source of sound comprises two microphone or like instruments 36, 37 in circuit with a differential telephone 39 and battery 38 and mounted on a rod 43 pivoted for movement about an horizontal axis 45 on a support 41 capable of rotation about a vertical axis. Direction is determined by moving the instruments until the sound in the receiver 39 is a maximum or minimum. The instruments 36, 37 are shown submersed in water in a pail 51 below the bottom 52 of a trench, and sights 49a, 50 carried by parallelogram links 42, 44 are provided to enable the direction to be noted on the walls of the trench. A device for transmitting sounds is described in which a rod or wire is secured to the middle cf a diaphragm and is caused to vibrate longitudinally by a rapidly rotated friction wheel.