You have data preparation issue earlier here since you mix both NIST SPH files with WAV extension and PCM WAV files with WAV.wav extension. You need to pick either first or second. For first you need to have lines like this in wav.scp:
FAEM0_SI1392 sph2pipe -f wav /home/avijoychakma/Downloads/Acoustic/Github/Kaldi/kaldi/egs/timit/s5/data/data/TRAIN/DR2/FAEM0/SI1392.WAV - |
for the second wav.scp need to look like this:
FAEM0_SI1392 /home/avijoychakma/Downloads/Acoustic/Github/Kaldi/kaldi/egs/timit/s5/data/data/TRAIN/DR2/FAEM0/SI1392.WAV.wav
Note that the first column (utterance id) doesn't have .WAV.
If you are not certain how to prepare such data with awk, you can use the scripting language you know to prepare the data, for example, Python.