Abstract: A casing unit is provided that includes a cylindrical peripheral wall portion of quartz or glass, a cover of metal, and a fixing unit configured to fix the casing unit in or to a housing of a hi-fi tube amplifier. Also provided is a hi-fi audio tube amplifier that includes a plurality of tubes configured to amplify audio signals, and a plurality of the afore-mentioned casing units. Each casing unit encloses one tube of the plurality tubes at three sides, and the fixing unit of each casing unit is configured to fix the respective casing unit in or to a housing of the hi-fi audio tube amplifier.

Abstract: There is provided a safety helmet (1) having an outer helmet shell (2), shock-absorbing material (3) and an electroacoustic transducer (5) for the delivery of a sound signal. The shock-absorbing material (3) has an outside (4) and is arranged within the outer helmet shell (2) with the outside (4) adjacent to the outer helmet shell (2). The electroacoustic transducer (5) is arranged in that case at the outside (4) of the shock-absorbing material (3).

Abstract: There is provided a safety helmet (1) having an outer helmet shell (2), shock-absorbing material (3) and an electroacoustic transducer (5) for the delivery of a sound signal. The shock-absorbing material (3) has an outside (4) and is arranged within the outer helmet shell (2) with the outside (4) adjacent to the outer helmet shell (2). The electroacoustic transducer (5) is arranged in that case at the outside (4) of the shock-absorbing material (3).

Abstract: There is provided a transducer system for an active noise compensation apparatus, which has a first end at the ear side and an electroacoustic transducer. The electroacoustic transducer has a diaphragm system and a magnet system, wherein the central region of the diaphragm system is curved towards the magnet system and is in the form of an inverted calotte. A sensor microphone is arranged in a volume between the first end and the region of the curvature of the diaphragm system.

Abstract: There is provided headphones for connection to an external active noise compensation device. The headphones have at least one earphone, a microphone near the ear, and a passive circuitry network for increasing the amplification of the external noise compensation device. In that way noise compensation in respect of the external noise compensation can be increased by increasing the overall amplification by the passive network.