Electrophysiologic recordings of certain neurovegetative manifestations produced by a sonic environment in the dental office, were able to demonstrate and evaluate the stressing and relaxing power of noise or music. The high speed and the telephone represent the most stressing elements in the dental office and show an intense electrodermal activity and respiratory disturbances (a decrease in the magnitude and specially an increase in the inspiratory frequency) characteristic of anxiety, stress and all emotional states. This neurovegetative manifestations are induced in the same way by dissonic music, irregular rhythms and aggressive sounds. On the contrary slow, regular melodious and harmonious music such as J. S. BACH's "Aria", induce a subjective and relaxing climate with neurovegetative reaction characteristic of a state of physiologic relaxation. Some correlations exist between different components of the character and the intensity of the neurovegetative reactions.