THE DESIGN AND TESTING OF NON LINEAR ACOUSTIC SYSTEMS
AG ELLIOTT · 2024
LINEAR ACOUSTIC SYSTEMSof each primary frequency at 35 and 39 kHz.Once generated, these secondary components proceed independently of the primary waves, suffering from the appropriate spreading loss and the appropriate frequency dependent attenuation loss.For sonar applications it is usually the production of the difference frequency which is of interest because it has several interesting properties and its formulation has been much studied.The advantages of Parametric Arrays can be summarized :-1.Low frequencies can be generated from relatively small high frequency arrays.2. Narrow beams can be produced at low frequencies from small arrays.3. The difference frequency beam either does not exhibit side lobes, or the side lobes are at an extremely low level.4. The difference frequency can be varied over a wide range with only a small change in beamwidth.The disadvantages of Parametric Arrays can be summarized :-1.Poor efficiency of the conversion to the difference frequency.2. Non linear distortion relies upon the physical characteristics of the medium which may or may not remain constant over the primary wave eld, and also may vary from day to day.'