Mock spectra synthesized from the z = 4 simulation with the QSO in a void. The solid line gives the Lyα forest spectrum without the influence of the QSO, the dashed line the spectrum from the radiative transfer simulation of the proximity effect for a QSO Lyman limit luminosity of L_νLL = 10³¹   erg   Hz^-1   s^-1. The grey line provides the results of a semi-analytical model of the proximity effect that differ significantly from the radiative transfer results behind the strong absorber at the middle of the spectrum. No noise is added to the spectra for better visibility.