Abstract: Device for generating acoustic waves comprising an assembly of substantially parallel deformable walls, made of a conductive elastomer material, the series of walls delimiting contiguous spaces therebetween alternately leading over two opposite surfaces of said assembly into two cavities, that are sealed relative to one another; and a rigid revolving chamber containing the assembly and having two sealed cavities opposite two surfaces. Two circular screened slots formed in the chamber define two vents that ensure communication between the cavities and the external acoustic medium. Means are also provided for applying, in a controlled and variable manner, a set of electric potentials to the walls in order to induce an electric field between the walls, consecutively active, and inactive for a control polarity, and inactive and active for the opposite polarity, so as to decrease the space covered by the field, i.e. and in series, and to thus equally increase the contiguous space.

Abstract: Device for generating acoustic waves comprising an assembly of substantially parallel deformable walls, made of a conductive elastomer material, the series of walls delimiting contiguous spaces therebetween alternately leading over two opposite surfaces of said assembly into two cavities, that are sealed relative to one another; and a rigid revolving chamber containing the assembly and having two sealed cavities opposite two surfaces. Two circular screened slots formed in the chamber define two vents that ensure communication between the cavities and the external acoustic medium. Means are also provided for applying, in a controlled and variable manner, a set of electric potentials to the walls in order to induce an electric field between the walls, consecutively active, and inactive for a control polarity, and inactive and active for the opposite polarity, so as to decrease the space covered by the field, i.e. and in series, and to thus equally increase the contiguous space.

Abstract: An active device for attenuating noise in a defined region using anti-noise waves. Sensors capable of detecting noise waves and the direction of the waves and providing data to a processor for controlling an electro-acoustic source so that the source emits anti-noise waves in a direction counter to the direction of the incoming noise waves.

Abstract: A device for attenuating noises generated by moving sources includes a set of arranged electroacoustic sources which emit an opposite antinoise wave in response to an incident wave as sensed and processed. The electroacoustic sources are arranged to preferably emit a synchronous antinoise wave having a radius of curvature approximating that of the incident wave.

Abstract: The ultrasonic pulse-echo method for locating and characterizing flaws in a partly submerged metal structure utilizes a device comprising an acoustic antenna (3), means (18) for preprocessing the echo signals, data transmission means (23-23') and a central processing unit (6).

Abstract: An apparatus for obtaining the farfield directional pressure intensity of a sonorous source placed in a fluid medium from pressure measurements taken in the nearfield of the source is disclosed. An acoustic antenna is placed in the nearfield of the source to map the acoustic pressure nearfield. The antenna consists of either a single receptor, or of two separate receptors, one fixed in position to define the direction and the other variable in position over the acoustic antenna. Each receptor is comprised of two oppositely facing parallel planar arrays of acoustic detectors separated by a predetermined distance. The detectors are arranged in each array in a predetermined matrix. The detector signals from both arrays are processed by either of two different methods, an additive or a multiplicative method, to obtain the farfield directional pressure intensity of the source.