Effects of the acoustic characteristics of natural sounds on perceived tranquility, emotional valence and arousal in patients with anxiety disorders

As a supplement to music therapy, natural sounds have become an effective means of relieving anxiety. This research investigates the natural acoustic characteristics that affect the perceived tranquility, emotional valence, and arousal in patients with anxiety disorders. This research conducted a subjective assessment experiment of natural sound involving 46 participants with anxiety disorders. It designed 56 natural sound stimuli by controlling four acoustic characteristic factors of natural sound: foreground sound types, the number of sound sources, the foreground-to-background signal-to-noise ratio (FBSNR), and the foreground sound duration ratio. Results show that patients with higher levels of anxiety may have a lower tolerance for mixed natural sounds. Natural sounds composed of two sources brought the highest emotional valence. When the number of sound sources increased from 2 to 6, perceived tranquility and emotional valence increased, while emotional arousal decreased. Anxious patients had the highest perceived tranquility and emotional valence of mixed natural sounds with a 75% foreground sound duration ratio. As the proportion of natural sounds in the foreground increased, there was a gradual decrease in emotional arousal. The number of sound sources, FBSNR, and the degree of anxiety may be the important acoustic characteristics that lead to the difference in anxious patients' perception. The acoustic characteristics of natural sounds need to be considered when creating a healing environment for anxious people.