Noise Gate

This effect removes background noise during quiet passages of an audio clip.

Threshold Specifies the level below which noise is removed. Set a threshold value high enough to remove noise. If important audio is cut off at the ends, reduce the threshold value.

Decay Specifies the speed of the transition between silence and sound. If you hear noise at the ends of important audio passages within the clip, decrease the delay value. If important audio passages sound cut off at the ends, increase the decay value.

Applying Effects > Audio effects included with Premiere > Noise Gate