Convert sound files to mp3 using lame

convertToMP3.sh

#!/bin/bash

# loop through files in the currently active directory
for f in *.$1
    do
        # case statement for arguments (you can convert wav, flac, and ogg to mp3)
        case $1 in
            wav)
                # converts wav files to mp3 using lame
                lame -b320 "$f" "${f%.*}".mp3
                ;;
            flac)
                # converts flac files to mp3 using flac/lame
                flac -cd "$f" | lame -b320 - "${f%.*}".mp3
                ;;
            ogg)
                # converts ogg to mp3 using oggdec/lame
                oggdec "$f" -o - | lame -b320 - "${f%.*}".mp3
                ;;
            *)
                echo "Usage: $0 {wav|flac|ogg}"
        esac
        shopt -s nullglob
        # check for mp3 files in current directory
        if [[ -n $(echo *.mp3) ]]; then
            # check if mp3 directory exists
            if [ ! -d "mp3" ]; then
                # creates mp3 directory if it doesn't already exist
                mkdir mp3
            fi
            # move all mp3 files to the mp3 directory
            mv *.mp3 mp3/
        fi
    done