[user104658]

As a more sensible contribution: it could be as simple as a subconscious situational inflection. For example, most people have a "phone voice" - they use a slightly different voice when they speak on the phone than they do when speaking face-to-face. It's really noticable if you're speaking to someone and then they get a phone call and take it...

"Yeah I was telling Bob about what happened at the weekend..."
*phone rings*
"Oh sorry I need to take this."
*voice pitch suddenly goes up*
"Haaaallooh?"


You can't see anyone in the DR... it probably is kind of like talking to someone on the phone.