Changing sound volume or bitrate of mp3 files with lame

Sometimes the recording level of mp3 files is very low. If I do some jogging next to a busy road, I cannot hear anything even when the sound volume is on the max. Therefore I have to increase the volume of the mp3 file. Using lame you can do it with the following script:

#!/bin/bash
while [ $# -ge 1 ]; do
infn=$1
outfn="${infn%%.mp3}_3x.mp3"
echo $outfn
lame --mp3input -v --scale=3 $infn $outfn
shift 1
done


The only problem is that filnames with blank spaces make this script to collapse. Have to figure out something else. Also the bitrate can be modified in this way:

#!/bin/bash
while [ $# -ge 1 ]; do
infn=$1
outfn="${infn%%.mp3}_LQ.mp3"
echo $outfn
lame --mp3input -V 9 $infn $outfn
shift 1
done


-V 9 is the lowest bitrate/quality -V 0 is the highest.