wn() {
    for pid in $(ps ax | grep afplay | grep -v grep | awk '{ print $1 }');
    do
        kill -9 $pid > /dev/null 2>&1;
    done;
    volume=$1;
    if [ -z $volume ]; then
        volume=1;
    else
        if [ $volume = "0" ]; then
            return;
        fi;
    fi;
    afplay $HOME/white-noise/white-noise.mp3 -t 100000 -v $volume &
}