Changing the playback speed of sound means changing the sampling interval (that is, changing the sampling frequency), but this frequency should still be above 2f (Nyquist rate), otherwise distortion will occur.

2. Realize the amplification and attenuation of sound signals.

The so-called amplification or attenuation does not change the characteristics of sound signals in frequency domain, but only changes the amplitude in time domain. At this time, an all-pass filter is needed to add an inherent parameter. Changing parameters can realize the function of sound signal amplification and attenuation.

3. Realize the mixing effect

The so-called mixing is to superimpose different sounds without affecting the characteristics of time domain and frequency domain respectively.

4. Realize the echo sound effect

The amplitude of time-domain echo decreases and the frequency-domain characteristics remain unchanged. Just add a delay to the original signal, add an amplitude parameter in the time domain, and then superimpose it with the original signal (the same as the third).

5. Realize the sound effect of male and female voice changes.

The change of male and female tones changes the amplitude of frequency domain, but it is linear.