The effects of sounds with low and high frequency content on postural stability

In this study, we evaluated the effect of simple sounds having different frequency on postural stability in quiet stance. Twenty-six healthy young adults (17 female and 9 male) were investigated, with an average age 19,0 ± 0,3 years. Experimental protocol included three 50s quiet standing trials, barefoot, in relaxed position, on an instrumented force plate. During the first trial the subjects were standing in silence, while during the second and third trial they were exposed to sounds with the frequency of 110 and 1000 Hz, respectively. The sounds were simple square waves at a level of 85 dB having 3 s single pulse duration and 2 s intervals. In each trial the center-of-pressure (COP) time series were recorded at a sampling rate of 20 Hz in both: the anterio-posterior (AP) and medial-lateral (ML) planes, and fed into the computer for subsequent analysis. It is conclusion that this finding lends support to different strategies observed during the exposure of our subjects to sounds having two different frequency contents, namely, normal postural strategy in the 110 Hz sound trial and automatic postural strategy in the 1 kHz sound trial.