The paper deals with the two various optimization processes finding such geometrical form of acoustical cavities which leads to excitation of predefined acoustic resonance. A computing times and accuracy of a solutions are compared. The attention is focused both on the first two formants that are important for vowel production, and on a domain between the third and the fifth formant. This frequency domain is important for voice timbre, namely for singing voice. The problem is solved by the help of transfer matrix method using conic acoustic elements. The results should help to have a physical background for voice rehabilitation, for teaching of operasingers at musical faculties and for better understanding of biomechanics of voice production.