This is what I've done:
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Copied your BSP to my folder portal 2/portal2/maps/.
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Created a folder called "Temp" into the folder portal 2/portal2/sound/ and copied your 8 sound files into it.
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Opened the BSP in pakrat and used the Add button. Browsed the folder /Temp I had created into my /sound folder and selected it directly (not each and every single music file inside, but the whole folder), and then clicked OK.
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Pakrat asked me about to "fix-up the paths" and I selected "Yes to all".
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Removed the /Temp folder from my /sound folder (to check if the embedded sounds actually work) and run the game... and the sounds are working...
I hope this steps list can help you to find out, man 
