According to a new study from the Donders Institute for Brain, Cognition and Behaviour in the Netherlands, our speaking voices actually register subtle changes along with our gesticulating limbs.
It’s all about acoustics: the pitch and volume of a voice change together with the movement of arms and hands. "That change is very subtle with a wrist movement," says Pouw. “It is less subtle with an arm movement. The pitch jumps up slightly whenever a movement slows down.”
According to Pouw, there are two different causes for these acoustic differences. One of the causes is the creation of vibrations. The forces involved in a movement cause vibrations in your body. Through the connective tissue that holds your body together, vibrations end up in your lungs, affecting the pressure in your lungs.
The second cause is muscle tension around your lungs that is needed to maintain balance. We do not merely use our arm muscles when we move our arms. “When starting the process of stopping your arm from moving, for example, other muscles are suddenly addressed to prevent your body from falling over. These muscles that maintain balance include muscles around your lungs.”
Acoustic information about upper limb movement in voicing [Wim Pouw, Alexandra Paxton, Steven J. Harrison, and James A. Dixon / PNAS]
Body language can also be heard [Donders Institute for Brain, Cognition and Behaviour]