Download audiaucity
Its freeware
Get the lame plugin for it, also free.
Its pc software
Copy the notification soud to computer. Open in audacity, then select the whole waveform of the audio file and in the menu of effect or somthing like that you can edit your wave file with things like amplify, it will automatically amp it to the max volume possible before peaking.
Then just select the wavefile again and select export selected audio to mp3, name it, and copy it back to the notifications folder on your phone.
Boom, much louder.
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