Abstract: A spectator hall at racetracks includes a roof with an inner ceiling decreasing in height from the racetrack, an opening directed to the racetrack, a back wall, a number of seats arranged with increasing height from the racetrack, at least one loud speaker at the ceiling near the opening, and an invisible front wall covering the opening. The invisible front wall is made from a stable material like glass or acrylic polymer, and is mounted stiffly e g by stiffening bars.

Abstract: A spectator hall at racetracks includes a roof with an inner ceiling decreasing in height from the racetrack, an opening directed to the racetrack, a back wall, a number of seats arranged with increasing height from the racetrack, at least one loud speaker at the ceiling near the opening, and an invisible front wall covering the opening. The invisible front wall is made from a stable material like glass or acrylic polymer, and is mounted stiffly e g by stiffening bars.

Abstract: A device for analysis and filtration of sound which comprises at least one frequency-linear filter, at least one frequency-logarithmic filter and a weighting means for the combining and non-linear weighting of the output signals from the frequency-linear filter and the frequency-logarithmic filter. The sound is fed parallel as an input signal to the two sets of filters. In turn, the output signals from the filters are fed to the weighting means where they are combined and weighted non-linearly on the basis of magnitudes relevant to the sound. A decision with respect to the identity of the sound is made in a decision means. The invention also relates to a method for analyzing and filtering sound with the aid of the above-mentioned device.

Abstract: Method and track when assembling rails and sleepers, the assembly being carried out with different degrees of resilient softness between rail and sleeper. The degrees of resilient softness are selected on the basis of a PN sequence.