How to balance audio volume level to the same ?

[invalid-password]

Dear all, my mission is to adjust volume level of many MP3 music before uploading to the music store (some MP3 are too low, some are too loud so I must adjust them to the same level).

Manually, I can use audio editing software to compare them by ear, and adjust one by one. But it may take a very long time.

Does anyone know a special tool to do it in a faster way ?
Or a digital processing algorithm ?

[golagoda]

I'm pretty sure what you're looking for is ReplayGain (http://wiki.hydrogenaudio.org/index.php?title=Replaygain)

[invalid-password]

Ah, thank you !

[hello_hello]

There's a link to MP3Gain on the replay gain page. It's the best program to use for MP3s as it adjusts them losslessly.
I keep all my music in a lossless format without altering the original volume and convert it to MP3 for use on my portable player.... after running MP3Gain on the MP3s to level out the volumes. It works a treat.