Two-beam transverse acoustoelectric voltage (TAV) spectroscopy has been employed in the characterisation of the high-resistivity semi-insulating indium phosphide (InP:Fe) samples. At low temperatures, an absorption peak at 1.409 eV is observed. The absorption peak is due to ether excitonic or surface state transition and is quenched upon shining bias light of energy 1.378 eV. The TAV amplitude increases slightly as compared with one beam when bias light of energy 1.13 eV is used. The quenching and the increasing of the sharp peak are interpreted as being due to the presence of a level of about 1.378 eV and a level of Fe impurity at 1.13 eV below the conduction band.