Accurate vocal compensation for sound intensity loss with increasing distance in natural environments.

Human abilities to adjust vocal output to compensate for intensity losses due to sound propagation over distance were investigated. Ten normally hearing adult participants were able to compensate for propagation losses ranging from -1.8 to -6.4 dBdoubling source distance over a range of distances from 1 to 8 m. The compensation was performed to within 1.2 dB of accuracy on average across all participants, distances, and propagation loss conditions with no practice or explicit training. These results suggest that natural vocal communication processes of humans may incorporate tacit knowledge of physical sound propagation properties more sophisticated than previously supposed.