A shock wave generator for use in an extracorporeal lithotripsy apparatus has a liquid-filled housing with an exit aperture for shock waves which are electromagnetically generated and conducted to a focusing element for focusing onto the calculi, and a plate-shaped element having a smaller cross-sectional area than the emitted shock wave is disposed in the path propagation of the shock wave. The plate-shaped element consists of a material having an acoustic impedance substantially corresponding to the acoustic impedance of the liquid in the housing, and having a propagation speed of sound therein which deviates from the propagation speed of sound in the liquid.

An acoustic lens having a variable focal length for employment in an acoustic propagation medium has two lens walls, namely an entry wall and an exit wall at least one lens wall being deformable for varying the focal length, a lens liquid located between the lens walls, and a pressure compensation system which maintains the static pressure of the lens liquid the same as the static pressure of the acoustic propagation medium adjoining the deformable lens wall.

The present invention relates to an acoustic focussing device for the focussing of ultrasonic and shock waves, particularly for the no-contact crushing of a concrement disposed in the body of a living being. Several boundary surfaces are arranged behind one another in the propagating direction of the sound waves, in which case adjacent gaps contain liquids of different sound velocities. At least one gap is connected with a non-adjacent gap. At least one of the boundary surfaces is deformable. At least one of the boundary surfaces can be moved in parallel to the propagating direction of the sound waves by means of which movement liquid is displaced between connected gaps and the radius of curvature of at least one of the deformable boundary surfaces is changed.

An ultrasound diagnosing device in which resolving power becomes uniform in a direction orthogonal to a scanning direction of sound rays over a wide range from the shallow to the deep. Ultrasound signals are transmitted and received by changing combination of the arrays associated with transmission and/or receiving of the ultrasound waves depending on a depth of an object for observation by using an ultrasound probe incorporating a plurality of unidimensional arrays of a plurality of ultrasound oscillators arranged in parallel and an acoustic lens having intrinsic focal points for every array on the side of an ultrasound radiation face of these arrays.

An acoustic filter is provided for attenuating or suppressing the negative pressure half-waves of an elastic wave, comprising an enclosure containing a liquid whose saturating vapor tension is close to the atmospheric pressure. A pump causes the liquid to flow and a regulator fixes its temperature.