Aggressiveness of the Growl-Like Timbre: Acoustic Characteristics, Musical Implications, and Biomechanical Mechanisms

THE TERM GROWL TYPICALLY REFERS TO LOW-PITCHED, rough sounds uttered by animals. Humans occasionally use growl-like voices to express excessive emotions. Acoustically characterized by loud dynamics and low values of the harmonic-to-noise ratio, growl-like sounds usually express anger and excitement associated with aggression. We propose a biomechanical model relating the aggressive characteristic of the growl-like timbre to the motor mechanisms underlying growl production in humans, highlighting how an abdominal muscle contraction enhances spine stability, which plays a critical role in physical attacks. This model was supported by the experimental data of activation of the deepest abdominal muscle during resting, singing, and growling. We found a significant positive correlation between the abdominal muscle activity associated with producing voice and the perceived aggressiveness intensity of voice. The cognition of growl-like sounds is discussed from the perspectives of biomechanics, evolutionary biology, and cognitive science.