bash functions arguments

This script is called fuu;

#!/bin/bash

speak() {
        case $1 in
                1)echo one
                ;;
                2)echo two
                ;;
                3)echo three
                ;;
        esac
}

speak

exit 0

when i run fuu 2 i expect "two" like result and i get nothing.

Please, What i'm doing wrong?

speak "${1}"

Thanks.