The only thing i can think of right now to boost the volume is to alter each file seperatly. Its a time consuming thing but can help you. And it works whit all wave files that can be found in SH3/Data/Sound folder.
Open the sound recorder in windows Start/program/acessoare/entertainment/soundrecorder.
(I hope that is the correct path coz iam not sure if i spelled it right in English coz i have a swedish keyboard and windows
)
Anyway when u open the sound recorder, from the dropdown meny, choose open, and then locate the wave file u want to change from the Sound folder.
Then choose from the Effects dropdown meny , Increase volume by 25%. (there is some other effects u can try also) Play the sound after each change u do and when u are satisfied whit the result just save the file from the dropdown meny.
There is some limitation how much u can increase coz to much can make the sound distorted.
Ive changed some explosions and weather effects my self so they are lauder.
Some thunder waves ive added eco too so they really sound like they are "rolling" away like in RL.
When it comes to the gramophone ive been looking my self how to increase the volume but havent found it so far.
Good luck
Vikinger.