## 4 Discussion
### Influence of Auditory Stimuli on Postural Balance  
The results showed that exposure to nature sounds during the CE condition on a firm surface led to a significant decrease in CoP\({}_{\text{vm}}\) values. This finding suggested a positive influence of natural auditory stimuli on postural balance. This can be explained through the lens of Dynamic Systems Theory [51], which posits that postural control arises from the dynamic interaction among sensory, motor, and cognitive systems. According to Dynamic Systems Theory, the body adapts to changes in the environment through self-organizing processes [52], where external stimuli such as auditory inputs interact with internal systems to maintain postural balance [53,54]. In this context, nature sounds may provide a stable auditory reference that supports the integration of sensory information and helps maintain postural control. In our study, nature sounds act as a stabilizing reference in individuals with intellectual disabilities, facilitating auditory-visual integration. In the absence of visual input (CE condition), individuals with intellectual disabilities may rely more on auditory cues. Nature sounds could enhance spatial awareness by providing a consistent, comfortable, and calming reference in individuals with typical development [55] and with intellectual disabilities [5]. This emotional modulation complements the sensory experience, reducing stress-related factors that can impact postural balance [56]. Previous research demonstrated that exposure to forest sounds resulted in significant physiological relaxation effects, including decreased heart rate and improved mood states, indicating enhanced parasympathetic activity [57]. It highlights the role of natural sound in promoting relaxation and reducing stress responses, which is crucial for motor control and stability [58]. Similarly, it has been found that pleasant natural sounds can increase parasympathetic activity while lowering cortisol levels [55]. It provides evidence that such auditory stimuli not only promote relaxation but also improve motor skills by mitigating the negative effects of stress on the body [55]. Moreover, the integration of auditory and visual information becomes crucial [59], especially during the CE condition. Indeed, the auditory system works with the visual system to create a complete perceptual map of the environment [59]. In the CE condition, where visual input is absent, the introduction of nature sounds may play a complementary role by providing auditory cues about the surrounding spatial layout. These auditory cues enhance the available sensory information, working alongside the reduced visual input to support spatial awareness. This complementary integration of auditory and visual information can facilitate more effective sensory processing, improving an individual's ability to maintain stability, adapt to changes, and respond effectively to postural challenges, ultimately promoting better balance control. In this regard, a previous study on supra-postural auditory-hand coordination further reinforces the relevance of auditory stimuli in postural control, particularly in dual-task conditions where auditory cues may assist in maintaining balance [60]. Furthermore, another study explored how auditory tasks, even those with minimal cognitive demand, can influence postural control and multitasking abilities, which is particularly relevant in our study, where auditory stimuli interact with cognitive and motor tasks [61]. On the other hand, the results indicated that exposure to noise sounds during the CE condition on a foam surface had a contrasting effect on postural balance in individuals with intellectual disabilities. There was a signifiicant increase in CoP\({}_{\rm{Vm}}\) values, suggesting heightened postural sway. Noise exposure likely disrupts brain regions critical for postural control [62], including the temporal lobe (processing auditory stimuli), posterior parietal cortex, and sensorimotor areas [15; 63].