Custom sounds can be cool, sometimes a little scatman on the server can be fun, but they can also be source of nerves. Now true, if they annoy you, on some servers you can turn them off, but what about downloading time? Well now you can keep your Fortress nice and clean and save your nerves.

Temporary solution:
If you want it as a temporary solution, in case you may want some sounds, but not right now, open the console and type:
This will allow you to download anything else besides sounds.

Permanent solution:
If you don't like sounds of any kind and don't want them ever, then go to the disk you installed steam (in this case, let's say it's D:\) and go to this path:
Now open the config.cfg file with Notepad or something similar and add this two lines anywhere in the file (I preffer at the end):

Now that should be it! Go on any server without worrying about kids spamming sounds or even downloading them at all!