The aim of study is the recognition on voice-prints. It is very important for CIM system and security system. The authors found out PPQ (Period Perturbation Quotient) is very useful for recognition of voice-prints for elder persons using FFT analyzing method of voices received DAT. The voices of 20 year old 20 male students and 50 year old male 10 teachers as testees are gatherd in 0 similar to 8 kHz DAT for /a//i//u//e//o/ for five seconds and the DFT and cepstrum are analyzed in 0 similar to 4 kHz based on Shannon's sampling theorem using NTT's F-KOUBOU. The fundamental frequency and the formants are obtained from the cepstrum and DFT of it.