When the speakerphone is on in the conference room, do you talk differently? Most people do.
They seem to breathe differently, hold their chest differently, pronounce their words differently … and they shout as if their voice had to reach the distance between them and the receiver.
But when our body is rigid, our words are spoken slower and we raise our voice, we sound different, we sound more aggressive and less credible. That may have a significant impact on how we are perceived on the other end.
Most modern speakerphones don’t need all that extra effort (they have adjustable speakers and microphones), you should speak authentically and normally… Your words will be credible, people will listen and you’ll be communicating more effectively.