Bash script to change volumen random

randomVolume.sh

#!/bin/bash
COUNTER=0
STARTWAIT=20
echo "waiting $STARTWAIT seconds!"
sleep $STARTWAIT 
echo "Random volumen >:D"
while true; do
        echo "number: $COUNTER"
        if [ $(( COUNTER % 2 )) -eq 0 ]; then
                RANDOMPERCENT=$( node -e "console.log(Math.round(Math.random()*50)+10)" )
        else
                RANDOMPERCENT=$(( ( RANDOM % 55 )  + 10 ))
        fi
        echo "volume: $RANDOMPERCENT %"
        echo "------------------------"
        amixer set Master $RANDOMPERCENT%
        let COUNTER+=1
        sleep 10
done