How to remove a small 2 second portion of audio from an mpeg video file in Mac?
Use ffmpeg (terminal tool).
https://github.com/fluent-ffmpeg/node-fluent-ffmpeg/wiki/Installing-ffmpeg-on-Mac-OS-X
Copy the audio into a separate file.
Then use ffmpeg again to silence desired part (https://stackoverflow.com/q/38180809/2792138 or https://stackoverflow.com/q/29215197/2792138).
Then merge new audio file with the initial video file, replacing old audio track.