[en] The complex charge ordering phenomena for polycrystalline La_1-xSr_xFeO₃ (1/3≤x≤2/3) have been studied by measuring the low temperature magnetization, resistivity and the longitudinal ultrasonic velocity (V_l). At low doping levels (1/3≤x≤0.5), a dramatic velocity increase is observed below 210 K, and the relative stiffening of V_l is proportional to the Sr concentration. The analysis suggests that this feature may correspond to the short-range charge ordering state of Fe³⁺ and Fe⁴⁺. At high doping levels (0.5< x≤2/3), the resistivity shows a sharp increase around 200 K, and the relative stiffening of V_l decreases with increasing x. This implies that the charge disproportionation transition 2Fe⁴⁺ → Fe³⁺ + Fe⁵⁺ occurs. In particular, the V_l of La_1/3Sr_2/3FeO₃ undergoes another softening transition below 181 K, which is attributed to the breathing-type distortion of Fe-O octahedron in the sequence...Fe³⁺Fe⁵⁺Fe³⁺.... The detailed form of the sound velocity anomalies in La_1-xSr_xFeO₃ (x = 1/3,2/3) is different, revealing the presence of complex charge ordering phenomena. To complete the ultrasonic characterization in La_1-xSr_xFeO₃, sound measurements were performed on La_0.1Sr_0.9FeO₃, whose ground state is a typical antiferromagnetic order, and the anomaly is small