In this experiment the spectra of gamma rays resulting from nuclear transitions of 22Na, 60Co and 137Cs are collected using a scintillation detector equipped with bMCA unit. The peaks of spectra are matched with the expected energies and number of counts were used to determine attenuation coefficients for Aluminium and Lead that were used as screens. The attenuation coefficient (µ) over screen material density (ρ) were found to be just a fraction (of the true value) away from the accepted values. For the following gamma energies: 2.506 MeV; 0.662 MeV; 1.275 MeV, µ/ρ were measure to be (0.04578±0.00571) cm2 g-1; (0.0717±0.0139) cm2 g-1; (0.0435±0.0052) cm2 g-1 correspondingly.