If you can't tell which group is larger based on a voice vote, you're not supposed to make a wild guess and assume a smaller group was simply louder (if you knew group sizes and how they'd vote, you wouldn't need to take the vote in the first place).
This strikes me as a fundamental misunderstanding of how parliamentary assemblies are actually run. The first rule for every chair, from the lowly leader of a Nevada caucus to the Speaker of the US House of Representatives to the Prime Minister of the United Kingdom of Great Britain and Northern Ireland, is that you
never call a vote if you don't know the outcome in advance.
You can actually see this process play out if you go back and read the original r/s4p post that brainchild posted way back when. Right in the middle there's a point where the liveblog goes "okay, now nothing is happening, the chair is taking a headcount of delegates, and they're just letting random people speak, not sure why."
I didn't get it before, but I perceive now that this is the chair getting a whip count -- sending somebody around to talk to every Hillary delegate and make sure they're in the room and ready to vote, tell them what the vote is, and clarify which side Hillary's camp wants them to vote on. Meanwhile they stall on the floor by giving random people speaking time.
Once the chair is confident from the reports from the whips that there are enough yea votes to make a majority and push the vote through, she'll call the vote. But not before. The only thing you're looking for in the vote is making sure that all the people who told you they'd vote yea are actually voting yea, because if they are, you know the vote passed.
That is how you can know from a voice vote who won even if one side is clearly yelling louder deliberately.
I understand that this will probably not sound less sketchy to those of you invested in finding sketchiness here. But it is how these votes actually run! And I'll observe that the Bernie camp did much the same thing, just a little less organized.