It's supposed to sound like a B, but the issue is not with using TTS rather than a real voice. The issue is having one recording instead of several. If you listen to Google Translate, it sounds pretty much the same, but listening to several sources can help you hear what the sound really is.
Two of the three forvo soundfiles like "d" to me; only one sounds like a clear "b"! I don't know what to make of this - probably a question for an audiologist. (I'm not sure that's the right word - someone who studies the interpretation of speech sounds is what I have in mind.)
The second one from SwedishFinn is a little bit unclear, but the other two are good, I'd say. The one from August is really articulated, while the last one is more or less how I would say it.
I can get that people are hearing different consonants with the TTL here on Duolingo (as of Nov 26 2014), but what I believe throw you guys off is the following vowel, the Ö. If you listen to these three, would you say that you hear a B or D?