@article{AbelBergweilerGerhard2006,
  author    = {Abel, Markus and Bergweiler, Steffen and Gerhard, Reimund},
  title     = {Synchronization of organ pipes : experimental observations and modeling},
  issn      = {0001-4966},
  doi       = {10.1121/1.217044},
  year      = {2006},
  abstract  = {We report measurements on the synchronization properties of organ pipes. First, we investigate influence of an external acoustical signal from a loudspeaker on the sound of an organ pipe. Second, the mutual influence of two pipes with different pitch is analyzed. In analogy to the externally driven, or mutually coupled self-sustained oscillators, one observes a frequency locking, which can be explained by synchronization theory. Further, we measure the dependence of the frequency of the signals emitted by two mutually detuned pipes with varying distance between the pipes. The spectrum shows a broad '' hump '' structure, not found for coupled oscillators. This indicates a complex coupling of the two organ pipes leading to nonlinear beat phenomena.},
  language  = {en}
}
@article{WegenerBergweilerZscherpeletal.2006,
  author    = {Wegener, Michael and Bergweiler, Steffen and Zscherpel, Detlef and Wirges, Werner and Gerhard, Reimund},
  title     = {Detection of elliptical oscillations and monopole breathing of organ-pipe bodies with piezoelectric polymer sensors},
  year      = {2006},
  abstract  = {In this paper, a measuring technique is presented for the detection of radial oscillations of tube walls excited by changes in internal air pressure. On organ pipes, the oscillations were investigated by means of piezoelectric polymer films slightly tensioned around the pipe bodies. Employing sensors with patterned electrodes, the well-known elliptical oscillation of the cross section as well as an additional monopole breathing of the organ-pipe body were detected. For the monopole breathing, a close relationship between the pressure distribution of the air-column resonances inside the pipe and the circumference variations along the pipe was observed},
  language  = {en}
}
@article{WegenerBergweilerWirgesetal.2005,
  author    = {Wegener, Michael and Bergweiler, Steffen and Wirges, Werner and Pucher, Andreas and Tuncer, Enis and Gerhard, Reimund},
  title     = {Piezoelectric two-layer stacks of cellular polypropylene ferroelectrets : transducer response at audio and ultrasound frequencies},
  issn      = {0885-3010},
  year      = {2005},
  abstract  = {Piezoelectric cellular polypropylene films, so-called ferroelectrets, are assembled in a stack with two active transducer layers. The stack is characterized with respect to its linear and quadratic response in a frequency range from 1 kHz to 80 kHz. A relatively smooth frequency response in the sound-pressure level is found for the individual layers as well as for both layers driven in phase. The piezoelectric response of the two-layer stack is twice the response of an individual layer over a rather broad frequency range. Furthermore, the influence of the preparation conditions on the resonance frequency and the effect of the quadratic distortion on the radiated sound are investigated both for the individual transducer films in the stack and for the stack system as a whole},
  language  = {en}
}
@article{WegenerBergweilerWirgesetal.2004,
  author    = {Wegener, Michael and Bergweiler, Steffen and Wirges, Werner and Pucher, Andreas and Gerhard, Reimund},
  title     = {Voided space-charge electrets : piezoelectric transducer materials for electro-acoustic applications},
  year      = {2004},
  language  = {en}
}
@article{WegenerGerhardWirgesetal.2003,
  author    = {Wegener, Michael and Gerhard, Reimund and Wirges, Werner and Bergner, Andr{\´e} and Bergweiler, Steffen},
  title     = {Breathing modes of organ-pipe bodies : experimental detection with ring-shaped piezoelectric-polymer sensors},
  year      = {2003},
  language  = {en}
}
@article{BergweilerBergnerGoerneetal.2003,
  author    = {Bergweiler, Steffen and Bergner, Andr{\´e} and G{\"o}rne, Thomas and Wegener, Michael and Gerhard, Reimund},
  title     = {Breathing modes and sound radiation of metallic organ pipes},
  year      = {2003},
  language  = {en}
}