Abstract: This publication discloses an acoustically active element formed in a multi-layer circuit-board structure (20, 22, 24, 25), a method for manufacturing it, and a multi-layer circuit-board structure. The acoustically active element includes an internal chamber (21) and a membrane (18) or beam arranged in connection with the internal chamber (21), which acts as a vibrating element and is connected electrically to external circuits, in order to produce or measure an acoustic effect. According to the invention, the resonance chamber (21) is formed inside the multi-layer circuit-board structure (20, 22, 24, 25), in connection with the process of manufacturing the circuit board.

Abstract: The invention relates to a method for attenuating magnetic interference in a test room (1, 2, 8, 9) equipped with a shield of ferromagnetic material, in which method the interfering magnetic field is measured and a compensating field is generated on the basis of the measurement result. According to the invention, the interfering field to be measured is resolved in three magnetic field components oriented in different directions, each one of said magnetic field components (x, y, z) is measured with the help of coils (3, 4, 5, 6) wound about the wall elements (1, 2, 8, 9) made from said ferromagnetic material in a manner wherein a flux component passing through at least one of the wall element (1, 2, 8, 9) made from said ferromagnetic material that is oriented parallel to one of said magnetic field components (x, y, z) is measured with the help of coils wound about said wall element.

Abstract: The invention relates to a method for attenuating magnetic interference in a test room (1, 2, 8, 9) equipped with a shield of ferromagnetic material, in which method the interfering magnetic field is measured and a compensating field is generated on the basis of the measurement result. According to the invention, the interfering field to be measured is resolved in three magnetic field components oriented in different directions, each one of said magnetic field components (x, y, z) is measured with the help of coils (3, 4, 5, 6) wound about the wall elements (1, 2, 8, 9) made from said ferromagnetic material in a manner wherein a flux component passing through at least one of the wall element (1, 2, 8, 9) made from said ferromagnetic material that is oriented parallel to one of said magnetic field components (x, y, z) is measured with the help of coils wound about said wall element.