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Background: Gamma-ray spectrometry helps in radiation shielding problems and different applications of radioisotopes. Experimental arrangements including broad beam geometries are widely used. The aim is to investigate and evaluate the γ-ray spectra via attenuation by environmental materials. Materials and Methods: The photo peak to nominated parts in the γ-ray spectra and the attenuation coefficients μb ⁄ρ from broad beam geometries are measured for the materials water, soil, sand and cement at the energies 0.662, 1.25, and 1.332 MeV with a 3" × 3" NaI(Tl) detector. Results and Discussion: The γ-ray spectra vary according to changes in the effective atomic number Zeff of the attenuator, the photon energy and the solid angle. The peak to total ratios are the most sensitive parts to variations in the experimental conditions and overturn in the region 0.663 MeV to 1.332 MeV. This is indicated as inversion trend. The results are discussed in view of Zeff and the experimental conditions. The intensity build-up is larger at the lower energy and larger scattering angles in agreement with Klein-Nishina formula and other results. The buildup factor B is 1 at high γ-energies and small scattering angles. Conclusion: The sensitivity to material characteristics decrease gradually from peak: to total, to Compton valley, to Compton plateau ratios. Rigorous collimation is necessary at small energies. Cement, of the largest Zeff , is characterized by the maximum broad beam mass attenuation coefficients μb ⁄ρ. The obtained results provide information to decide for the suitable experimental set-up based on aim of the work.