Effects of the direction of sound stimuli on body sway in young healthy individuals

Sound has been suggested to improve human balance control; however, the optimal direction of sound presentation is unclear. This study aimed to evaluate the effect of sound presentation direction on postural stability. Thirty-one healthy young volunteers (mean age 24.1 ± 2.6 years) participated. Posturography was performed in five acoustic conditions (white noise at 60 dBA delivered from the front, back, left, and right and a silence condition), two visual conditions (eyes open/eyes closed), and two standing conditions (foam surface/firm surface). The total sway area, mean sway velocity, and root mean square (RMS) sway were measured. A three-way repeated-measures analysis of variance with a within-group factor was conducted, followed by post hoc pairwise comparisons using Bonferroni adjustments. When standing on foam with the eyes closed, total sway area and RMS sway were significantly smaller with sound from behind than in silence, and mean sway velocity was significantly smaller with sound from the front than from the left. Sound presented from behind or the front reduced posturography parameter values, suggesting that the direction of sound presentation helps stabilize postural sway.