| 摘要 |
PURPOSE:To attain the signal band compression and expansion of a signal without changing the time axis by applying Fourier transformation to a signal extracted by multiplying a window function having a length and a coefficient of a limited time or over with a voice signal and compressing and expanding the sigjnal at a frequency axis. CONSTITUTION:The voice signal in 6.4kHz inputted to a terminal 1 through an LPF of 3.2kHz is subject to A/D-conversion 2 by a clock of 6.4kHz, inputted to a shift register SR3 and further latched to an SR4. The window function having the length and coefficient being a limited time or over is multiplied to the signal from the SR4 by a multiplier 5, its output of the time axis is converted into the frequency axis by the Fourier transformation FFT circuit 6 for a short time, a prescribed coefficient is applied by a vertical device 7, its output is fed to a spectrum transformation circuit 8, where the output is subject to compression and expansion on the frequency axis. The output signal of the circuit 8 is multiplied with the coefficient by the multiplier 9 and the frequency axis is inverted into the time axis by an inverting FFT circuit 10 and its output is multiplied with the window function by a multiplier 11 and inputted to the SR12. The output of the SR12 is added by an SR13 at each corresponding word and outputted after A/D converted 14. |
