Just to add, you don't need the sox section of the command, it works the same i.e. audio in from mic is echoed into the earpiece without any delays
pi@sbitx:~ $ arecord -Dplughw:CARD=5,DEV=0 -t wav -f S16_LE -r 96000 -c 2 -| aplay -D hw:CARD=2,DEV=0 -
