Acoustic absorber and sound-absorption method

The present invention relates to an acoustic absorber and to a sound-absorption method for damping sound in a fluid flowing in a duct. An acoustic absorber () comprises a housing or wall (), defining an interior absorber chamber () connected by openings () to a duct () to reduce the sound in the duct (). The natural frequency and impedance of the absorber () are variable, so that the absorber () can be adapted to a sound field in the duct () in a manner corresponding to the respective operating conditions. Such adaptation is achieved mechanically, for example, by an elastic membrane () for varying the volume of chamber (), or thermally, for example, by a heating wire () or a wire braid ().