When we move our arms—especially with some effort—muscles are activated that rotate the arm, but also muscles involved in maintaining balance. These muscle contractions also affect the lung volume as they attach to the rib cage, which in turn affects the loudness or intensity of our voice. The study shows that vocalizations and movement are intimately linked through whole body biomechanics.
In the experiment, participants were asked to produce a stable ‘ah’ sound while making brisk arm movement. Simultaneously muscle activity of arm- and postural muscles was recorded.
The study shows that the body and voice are more connected than we might think. “The voice responds to full-body movement,” the researchers explain. “This means that when we gesture with emphasis, it may directly affect how we sound.” These findings challenge the idea that we control our voice separately from our body. Instead, it suggests that speech and gesture have evolved together and influence each other in real time. Humans exploit this link, using gestures not only to visually emphasize their speech, but also to physically put emphasis into their vocalizations.
This research could provide new perspectives on speech therapy and on how robots can be made to move and sound more like humans.
Read the full study in Proceedings of the Royal Society B: Biological Sciences.