Start by checking how you added the data to the DB: unless it is correctly stored you can't use it.
The most common mistake with images or sound samples is to try and concatenate strings to form the SQL INSERT statement - see here:
Why do I get a "Parameter is not valid." exception when I read an image from my database?[
^]
If you have checked that and are happy that the data is definitely the right length and contains valid sound info, then use the debugger to find out exactly what the returned data looks like, and compare that to the original file content (using a hex editor)
Sorry, but we can't do any of that for you!