Shell Script Audio Logger
This looks quite fine, except this part:


if [ "$PART" -eq 0 ]
then
arecord -f cd -c 1 -d$DURATION -t raw -v -v | lame -b 128 -q2 -mm 
-r - ./Documents/"LoggerAudio "$DAY-$MO-$YR\ $H"00".mp3
else
arecord -f cd -c 1 -d$DURATION -t raw -v -v | lame -b 128 -q2 -mm 
-r - ./Documents/"LoggerAudio "$DAY-$MO-$YR\ $H"00 - Part - "$PART.mp3
fi



One problem here is indentation:
it's a lot easier to read when the branches of conditionals are indented.

A bigger problem is that a long and complicated pipeline is duplicated (looks copy-pasted),
which is a bad practice, because it's prone to errors.
Since only the filename is different,
you can set that in the conditional branches,
and then write the complicated pipeline only once.

if [ "$PART" -eq 0 ]
then
    out="LoggerAudio $DAY-$MO-$YR ${H}00.mp3"
else
    out="LoggerAudio $DAY-$MO-$YR ${H}00 - Part - $PART.mp3"
fi
arecord -f cd -c 1 -d$DURATION -t raw -v -v | lame -b 128 -q2 -mm -r - ./Documents/"$out"


Notice that I also slightly simplified the writing style of the filename.