  The coherent acoustic waves can be created by InGaN double quantum wells. We
measured the signals information of the coherent acoustic waves at the
interface of GaN/glycerol to obtain the attenuations of glycerol at 295 K and
120 K by the femto-sec laser pump probe technique in THz regime. The
attenuations of glycerol are calculated by using the acoustic mismatch model
(AMM) through the complex acoustic impedance. We compared pump probe results
with inelastic neutron scattering (INS) and inelastic X ray scattering (IXS),
found they are matched within 0.5 THz at room temperature. The glycerol
attenuations are found increasing monotonically to 1.75x10^8 m^(-1) and
1.3x10^8 m^(-1) till 0.5 THz by the pump probe technique at 295 K and 120 K,
respectively.
