Many of the effects being looked at affect the overal volume of a signal. The processing is all done in floating point numbers and converted to 16 bit shorts for playing.

In the analogue world, when a signal attempts to go beyond what the boundaries of what an analogue amplifier is capable of reproducing the signal is clipped resilting in a flat topped waveform.

For instance a sine wave (red) clipped at 75% of its full scale value (blue).