  We analyze results for the Boson Peak from the neutron time of flight
spectroscopy data on Ge-As-Se, and Raman spectra data on m-TCP and OTP, using a
recent mode coupling model that takes into account the coupling of density
fluctuations with vibrational modes in presence of defects in the supercooled
state.
  From the experimental results for different materials we observe that for
more fragile systems characterized by increasing fragility parameter m, a
slower relaxation of the defect-density correlation is needed to give rise to
the observed peak in the spectra.
