Implemented Model for Post-Masking

As can be seen in Fig. , the post-masking effect varies with the length of the masker burst, from 5-10 ms up to 200 ms. This effect is exploited in the coder in by a one-pole filter on the masking threshold over time:

$$M'_t = 0.85M'_{t-1} + 0.15M_t$$ (19)

The final output mask is then taken as $M_t = \max(M'_t, M_t)$. With this definition, a short burst does not affect $M'_t$ much, while a longer burst will sustain the masking for a number of frames even though $M_t$ goes low again.