Pre-emphasis: In this step signals are passing through a filter. Pre-emphasis procedure emphasizes the higher frequencies. This process will increase the energy of signal at higher frequency. 21
Yn =Xn -0.95 X n-1 (1)
The goal of pre-emphasis is to compensate the high-frequency part that was suppressed during the sound production mechanism of humans. Moreover, it can also amplify the importance of high-frequency formants. 22
Framing: After pre-emphasis process we split the signal into short –time frame of 20ms -40 ms duration. Usually the frame size (in terms of sample points) is equal to power of two in order to facilitate the use of FFT. Overlapping is used to produce continuity within frames. The voice signal is divided into frames of N samples. Adjacent frames are being separated by M (M