In Belgium the only reason full-face burkas and niqabs are outlawed is because you need to be recognisable. There isn't a burka prohibition but rather one against clothes/masks/... in general that can make it difficult to identify somebody.

The only exception is when it's carnival ergo the reason why it's called the carnival law here. And I assume that is also the case in most European countries.

When you are wearing a headphone you can be still identified.