for f in *.flac; do flac -cd "$f" | lame -b 320 - "${f%.*}".mp3; done

or

for a in ./*.flac; do ffmpeg -i "$a" -qscale:a 0 "${a[@]/%flac/mp3}"; done

find . -type f -name "*.flac" -print0 | while IFS= read -r -d '' file; do echo "$file"; flac -cd "$file" | lame -b 320 - "${file%.*}".mp3; done

find . -type f -name "*.mp3" -print0 | while IFS= read -r -d '' file; do echo "$file"; lame -b 192 "$file" "${file%.*}".192.mp3; done

find . -type f -name "*.mp3" -print0 | while IFS= read -r -d '' file; do echo "$file"; [[ $(file "$file" | sed 's/.*, \(.*\)kbps.*/\1/' | tr -d " ") -gt 192 ]] && lame -b 192 "$file" "${file%.*}".192.mp3 && mv "${file%.*}".192.mp3 "$file"; done