I recently added a house to projects with a Nether portal inside. This was cool but I realized that the portal sounds are quite annoying and I had turned mine off, however whoever had downloaded the house would probably still have their portal sounds still on. This can be a problem because you can't just delete the sound file, minecraft will just restore them, so we have to do a little work. First locate your portal.ogg file, it is in .mincraft/resources/newsound/portal folder, you need to back that up, just rename it portal.bak or .old now, open create a text file by right clicking on the desktop and choosing new then text, go to file, save as and save as portal.ogg. now right click on your new portal file and go to properties, choose read only, this will prevent Minecraft from rewriting the file. slap that baby in your portal folder and enjoy the silence!