For any sonochemical process, the maximum effect depends on a range of conditions and process optimization can lead to a considerable savings in electric power. In this paper, the optimization investigation focuses on the acoustic features of the ultrasonic reactor, such as the transducer impedance and the frequency components of sound pressure with respect to the reactor configuration, namely the liquid height and the upper end configuration for a cylindrically shaped sonochemical reactor. Measurements were carried out for the liquid heights varying in the range of 142 to 163 mm with and without an aluminum reflector mounted on the upper end of the liquid column for a ultrasonic frequency of 129 kHz. Our data revealed that the impedance of the transducer and the sonochemical efficiency are strongly dependent on the liquid height and on the upper part configuration of the reactor: free or fixed end. Moreover, the maximum sonochemical efficiency was attained at liquid heights where the transducer impedance showed minimum values, the distance between two consecutive maxima being lambda/2 (where lambda = 11.6 mm in this work). The frequency components of the sound pressure into the liquid were also investigated, and it was discovered that the maximum sonochemical efficiency was reached when the harmonic components were enhanced and subharmonic were reduced. An automatic control system for increasing the sonochemical efficiency by maintaining the impedance at the minimum level with the help of frequency is presented here.