Abstract: Acoustic actuator plate structures are used in acoustic applications. The acoustic actuator plate structure according to the invention contains an electret material and comprises a structurally weaker electret layer (1), where the specific resistance of the electret material is at least 10 ?m and the yield point of it is high, and a structurally stronger support structure layer (2), where the plastic region of the support layer material is wider than the plastic region of the electret material. The electret layer (1) can be formed of a material that retains its electret properties extremely well even in high temperatures and humid conditions. This material may be brittle. The support structure layer (2) provides mechanical and structural strength to the acoustic actuator plate structure.

Abstract: The invention relates to a plate-like electrostatic actuator which comprises at least one plate-like stator with an electrode formed on its surface and at least one moving diaphragm, and in which a signal is transmitted to the electrode along a signal line. In the solution of the invention, the delay directing the sound field of the actuator is formed at least partly of an RC circuit composed of components of the actuator.

Abstract: The invention relates to a plate-like electrostatic actuator which comprises at least one plate-like stator with an electrode formed on its surface and at least one moving diaphragm, and in which a signal is transmitted to the electrode along a signal line. In the solution of the invention, the delay directing the sound field of the actuator is formed at least partly of an RC circuit composed of components of the actuator.

Abstract: Acoustic actuator plate structures are used in acoustic applications. The acoustic actuator plate structure according to the invention contains an electret material and comprises a structurally weaker electret layer (1), where the specific resistance of the electret material is at least 10 ?m and the yield point of it is high, and a structurally stronger support structure layer (2), where the plastic region of the support layer material is wider than the plastic region of the electret material. The electret layer (1) can be formed of a material that retains its electret properties extremely well even in high temperatures and humid conditions. This material may be brittle. The support structure layer (2) provides mechanical and structural strength to the acoustic actuator plate structure.

Abstract: An electromechanical transducer comprising at least one transducer element which has a multilayer structure comprising at least two layers such that the transducer element is capable of changing its thickness. The transducer element allows air to flow inside the transducer element in the direction of thickness thereof and inside and out of the transducer element through at least one surface of the transducer element in the direction of thickness of the transducer element. The transducer element can be used e.g. for transforming energy from mechanical energy into electric energy and/or vice versa.

Abstract: An electrostatic transducer, a method for connecting the same and a manufacturing method. The electrostatic transducer comprises at least one stator, which comprises an insulating layer and a conducting layer, and a film element which is arranged to vibrate in response to voltage supplied to it and which is provided in such a manner that an air gap is formed between the conducting layer and the film element. The electrostatic transducer also comprises at least one fastening edge arranged on the outer edge of the electrostatic transducer, the fastening edge being arranged to be fastened to a fastening element of a second electrostatic transducer.

Abstract: The invention relates to a method and an apparatus for sound processing, where sound is attenuated by measuring it and by producing with an actuator a sound field of opposite sign in view of the original sound field. A desired value signal (I) is supplied to the actuator which reproduces the signal. To the actuator is attached a sensor, measuring sound pressure, and the difference of the sensor signal (B) and the desired value signal (I) is applied as high gain feedback to the actuator. As a consequence, sound not pertaining to the desired value signal (I) can be attenuated in a simple manner, and sound in accordance with the desired value signal (I) can be produced simultaneously with the same apparatus.

Abstract: The invention relates to a method of and an arrangement for damping a wall movement. In the invention, the strength of an electric field between a surface of a wall and an air-permeable mass plate parallel with the surface is controlled to provide a force opposite to the wall-moving force. A sound wave, for instance, may cause a force moving a wall back and forth, which force is cancelled by the opposite force by means of the method and arrangement of the invention, whereby the movement applied to the wall by the sound wave can be stopped.

Abstract: The present invention relates to an electroacoustic transducer where the voltage of a capacitive acoustic element is controlled by charging and discharging the charge of the element via an inductance (L) by fast switches (K1, K2). In the case energy unconverted into the acoustic energy of the transducer can be transferred to an energy storage of an electrical circuit formed by the inductance (L) and the capacitance (C1, C2, C0) during each control sequence and in this way the transducer can be made to operate with a good coefficient of efficiency.

Abstract: An acoustic element comprising a platelike active element. The platelike active element comprises creases. The creases can be produced such that the platelike active element forms a space comprising at least one opening and/or gap, whereby the space and the opening and/or the gap constitute a Hemholz resonator.

Abstract: The invention relates to an acoustic element and method for sound processing. The acoustic element (1) is made of a porous stator plate (2) which is either electrically conductive or plated on at least one of its surfaces to be conductive. A moving diaphragm (3, 3a, 3b) has been attached to the stator plate (2). To measure as well as produce sound pressure and particle velocity, the equipment comprises two pairs of aforementioned acoustic elements (1). Elements serving as sensors control elements serving as actuators to attenuate and absorb sound.