When compared to nature sounds, exposure to mechanical sounds evokes higher levels of perceptual and physiological arousal, prompting the recruitment of attentional and physiological resources to elicit adaptive responses. However, it is unclear whether these attributes are solely related to the sound intensity of mechanical sounds, since in most real-world scenarios, mechanical sounds are present at high intensities, or if other acoustic or semantic factors are also at play. We measured the Skin Conductance Response (SCR), reflecting sympathetic nervous system (SNS) activity as well as the pleasantness and eventfulness of the soundscape across two passive and active listening tasks in (N = 25; 14 females, 11 males) healthy subjects. The auditory stimuli were divided into two categories, nature, and mechanical sounds, and were manipulated to vary in three perceived loudness levels. As expected, we found that the sound category influenced perceived soundscape pleasantness and eventfulness. SCR was analysed by taking the mean level across the stimulus epoch, and also by quantifying its dynamic. We found that mean SCR was modulated by loudness only. SCR rise-time (a measure of the time it takes the skin response to increase from baseline to its max value) correlated significantly with soundscape pleasantness and eventfulness for nature and mechanical sounds. This study highlights the importance of considering both loudness level and sound category in evaluating the perceptual soundscape, highlighting SCR as a valuable tool for such assessments. Significance Statement While loud mechanical sounds are often deemed more unpleasant than nature sounds, it remains unclear whether this response is due to loudness itself or the origin of the sound. This study disentangles these effects by using skin conductance responses, a window into the body’s automatic, unconscious reactions, to reveal that loudness is a key driver of physiological arousal. However, the listener’s subjective perception of how pleasant or eventful a soundscape feels also significantly shapes this response. These findings highlight the dynamic relationship between physical sound properties and perceptual experience in shaping our reactions to everyday acoustic environments.
Erfanian et al. (Thu,) studied this question.