Use SoX to batch convert audio files to a different format. First arg is currently existing format, second arg is the new audio format. All files will go into a new folder. Example: sh convert_audio.sh wav ogg -> will convert all .wav files in current directory to .ogg files, and place them in a folder named 'ogg'.

convert_audio.sh

#!/bin/sh

mkdir $2

#adds a '.' to the beginning of the passed in string, if it is not already there
add_dot_to_beginning_of_args () { 
	initialLetter="$(echo $1 | head -c 1)"
	one=$1

	if [ "$initialLetter" !=  "." ] ; then
		one=".$1"
	fi

	echo $one
}

#add the '.' to the front of the passed-in filename extensions, if it is not already there
one=$(add_dot_to_beginning_of_args $1)
two=$(add_dot_to_beginning_of_args $2)

#loop over all files in current directory with $1's extension
for file in $(pwd)/*$one; do 
	filename=$(basename "$file") #filename without path
	name=$(echo $filename | cut -f 1 -d '.') #just filename, no extension
	sox "$name$one" "$2/$name$two" #convert the audio files to the new extension
done