As you know Mp3 is a lossy format unlike Flac (loss less) and therefore ripping mp3 audio into high quality files requires tools. If you want to increase mp3 quality without changing the bitrate or if you want to change the bit rate of the mp3 file to increase the file size then here are some online and freeware ways to do the same.
Note that you will not really get very high quality mp3 output but this can upgrade the volume of your mp3 files.
Mp3 Quality Increase With Bitrate
One of the effective way to increase the bitrate of mp3 file is by using freeware software’s. Software like nero audio encoder or audio encoders will increase bitrate to 320kbps. Note that when the bitrate is increased, the mp3 file size also increases and you can compress it once again but this will turn out to provide lossy format.
Related: Compress Mp3 File Size
Increase Mp3 Loudness Volume
Vloud is a free online service that is helpful for PC and laptops which plays songs at an high volume. With this online tool, you can increase the volume sound of your mp3 file to light, loud, louder and download the file again onto your desktop. Browse the mp3 you want to increase the sound quality and upload to vloud, wait till the process completes and you will have an decent increase in the mp3 sound.