  Guided Acoustic Wave Brillouin Scattering (GAWBS) generates phase and
polarization noise of light propagating in glass fibers. This excess noise
affects the performance of various experiments operating at the quantum noise
limit. We experimentally demonstrate the reduction of GAWBS noise in a photonic
crystal fiber in a broad frequency range using cavity sound dynamics. We
compare the noise spectrum to the one of a standard fiber and observe a 10-fold
noise reduction in the frequency range up to 200 MHz. Based on our measurement
results as well as on numerical simulations we establish a model for the
reduction of GAWBS noise in photonic crystal fibers.
