Well they could just do what the characters in sci fi books do when they want to speak without their voices being transmitted, they can touch their spacesuit visors together. The soundwaves can travel between the suits due to contact.

I'm not arguing against what you stated because I know that's not the point you were making. Just adding a comment

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I was just sitting here contemplating the immortal words of Socrates who said, "I drank what?"

"Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot." --Carl Sagan "Pale Blue Dot"