Improvements in or relating to the measurement of the time occupied by sound in travelling to and from a reflector

Abstract

Abstract 174,355. Blondel, A. E. Jan. 19, 1922. Short-time movements. - Comprises apparatus for timing the short interval between an initial sound and its echo, and consists in means for measuring the distance travelled by a simultaneous disturbance propagated through an acoustic system. The echo, heard in one telephone T', is compared with a sound produced in a second telephone T by a disturbance which has travelled at a known speed over a measured section AM1, AM2 . . or AM, of a " propagator " or sound-conveying system AB, adjustments being made until the sounds in the two telephones are heard simultaneously. In one form of the invention (not shown), the " propagator " AB comprises a spiral tube filled with air, hydrogen, water, alcohol, ether, or the like, and flared at the far end to prevent reflection of the disturbance travelling in it. In a further modification, the propagator AB comprises an artificial line made up of inductances and capacities along which an electric disturbance travels at a low rate. In further modifications, the propagator AB may comprise a rod, wire, cord, or metallic strip capable of transmitting longitudinal, transverse, or rotational disturbances. Thus in the form shown in Fig. 12, a cord H is attached at its lower end to a pivoted bracket 35, which receives a blow from the striker Q<1>. The disturbance initiated by the striker Q<1> travels up the wire, in one form, until it breaks contact at l<1> with a sliding contact-maker, or, in another form, until it affects a microphone m. In either case, a sound is produced in the telephone T, which is protected from any sound due to the reflexion of the disturbance by a short-circuit or disconnection applied by the time-lag switch 38, the reflection itself being checked by a magnet 36. The sliding contact-maker or the microphone is adjusted until the sound produced in the telephone T coincides with the echo of the initial sound. Instead of a cord H, a flat steel or bronze strip, loaded for transmitting torsional disturbances, may be used. When such a disturbance has travelled an adjustable distance along the strip, it causes a sound in the telephone bv affecting a microphone or causing the strip to make or break an electric circuit or to break a magnetic circuit, means being described for preventing any subsequent reflected disturbance from having a similar effect. Reflection is checked by arranging a pawl and ratchet at the far end of the strip, or the telephone may be put out of action by the disturbance reaching that point. The steel strip may be replaced by a tube cut into a helix, or a loaded helical spring, or a series of coaxial discs connected by springs, or a ladder comprising two wires connected by cross-pieces.

Inventors

No inventors recorded.

Bibliographic Details