Non-verbal communication is not lost with audio-only podcasts. There are subtle clues such as gestures with the head and arms, tension in the body, and variations in breathing which listeners are aware of subconsciously. These clues color the listener’s impressions.
Keep in mind that your expectations about people are communicated to them nonverbally. It has been demonstrated, for instance, that teachers who expect greater things from their pupils can, without ever saying anything, have a positive effect on their work and grades. By feeling particularly excited when you’re meeting someone, you will communicate this to him or her in a powerful way. Some have claimed to get great results by simply thinking the other person is handsome or good-looking.~ Robert Greene, Daily Laws
It’s interesting to consider our options in any conversation: intentions we set beforehand, gestures and physical expressions to use, ideas and questions considered during our preparation, and many more. Each option is going to affect our non-verbal communication. Anyone present, or who sees a video recording, has the opportunity to see the full communication. They are not going to notice audio subtleties within the overall experience.
When the visual is removed however, the audio subtleties remain. My smile before speaking is gone, but the subtlety in my voice remains. Every small clue in the audio, without the visual, suddenly becomes significant to the listener.
Listeners aren’t likely to notice consciously, but they do notice. Some clues, like laughter, are easy to point to as a reason for, “that conversation was fun.” But listeners are more likely to say (for example), “that conversation was profound” or “serious” without really knowing why they have that impression. Slight changes in timing and cadence, a catch in a breath, a moment of bodily tension—just the slightest imprints of non-verbal communication—impact the listener’s impressions.
Our lives normally have a visual component, and so we don’t notice nuance in our aural environment. But when the visual is removed, we are subconsciously drawn to the smallest details in the audio. It’s not that audio-only is better or worse, it’s simply so different that we perceive it as more interesting, more engaging, more, “I don’t know, there’s just something about audio!”