Mechanical linkage projectors

Fundamental constraints pertaining to resonant types of low-frequency underwater projectors explain why a nonresonant approach has permitted the design of a relatively small, efficient, and inexpensive projector whose output frequency, piston motion amplitude, and operating depth are all independently controllable. The resulting unit is inherently a “standard” source not requiring calibration by auxiliary instruments. Overall energetic efficiencies of 1% to 2% have been achieved in operating at 15 Hz and shallow depths (500 ft). Design principles have been worked out for achieving instantaneous switching of output amplitude, frequency, and phase as well as for the simultaneous output of two or three anharmonically related signals. The first unit displaces about 216 lb, uses a 1/12th HP electric motor to generate a 15-Hz signal at a source level of 171 dB re 1 μPa at 1 m, and would cost about $7000 each to manufacture in lots of ten.