FFMPEG trim silence from audio files and concatenate them with specified lengh silence interval.

trim_and_combine_two_audio_files.sh

#!/bin/sh

in_1_fname=./wavefile1.wav
in_2_fname=./wavefile2.wav
out_fname=./out.wav
threshold=-50dB

pause=1.5 # seconds

ffmpeg -loglevel verbose -y \
-i $in_1_fname -i $in_2_fname -filter_complex \
"\
[0:a] silenceremove=stop_periods=1:stop_duration=1:stop_threshold=$threshold [first],\
[1:a] silenceremove=start_periods=1:start_duration=0:start_threshold=$threshold [second],\
aevalsrc=exprs=0:d=$pause[silence],\
[first] [silence] [second] concat=n=3:v=0:a=1[outa]\
" \
-map [outa] $out_fname