Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Health and Rehabilitation Sciences

Collaborative Specialization

Music Cognition

Supervisor

Ewan Macpherson

2nd Supervisor

Jessica Grahn

Joint Supervisor

Abstract

Engaging with natural environments has been shown to reduce stress and improve cognitive performance. This beneficial effect is attributed to natural stimuli refreshing our ability to focus by providing a respite from constant demands on our attention. In addition to this effect, natural stimuli may also restore emotional and physiological well-being, mitigating the negative effects of stress. The effectiveness of this restoration has been demonstrated by comparing the effects of exposure to recordings of natural soundscapes versus urban soundscapes. Natural environments often include frequencies that are beyond the range of human hearing (ultrasound). Stimuli with ultrasound appear to increase alpha activity in the brain more than stimuli without ultrasound, which is significant because increased alpha wave activity is associated with a state of relaxed alertness. This relaxed alertness could, in principle, assist with tasks that require focused attention, thereby improving cognitive performance. Moreover, elevated alpha wave activity is typically linked to decreased stress levels, suggesting that exposure to natural soundscapes with ultrasound may offer enhanced restorative benefits. It is presently unknown whether incorporating the ultrasound range into recordings of natural soundscapes can enhance their cognitive and perceived restorative properties. To investigate this, we conducted a randomized controlled trial comparing the effects of different types of soundscapes (nature or urban) with different bandwidths (audible-only or audible plus ultrasound) to quantify their effects on cognitive performance and perceived restoration. We used a backward digit span task and an n-back task to both deplete and assess attention. Participants completed the Positive and Negative Affect Schedule (PANAS), Perceived Restoration Scale as well as cognitive fatigue, and aesthetic assessments to measure perceived restoration. Both the task blocks and assessments were completed before and after the soundscape intervention. The results revealed no significant effect of ultrasound on cognitive performance. However, ultrasound exposure was found to increase cognitive fatigue. Additionally, there was no effect of ultrasound on affective or restorative outcomes. Notably, the environment, mediated by aesthetic preference, most accurately predicted the subjective outcomes of soundscapes, showing significant effects on emotional regulation, perceived restoration and cognitive fatigue.

Summary for Lay Audience

Engaging with nature after mentally and emotionally fatiguing activities can help us recharge and think more clearly. Natural sounds, such as birds, water, and wind, can provide our brains with a break from the usual demands on our attention. They may also contribute to our happiness and well-being by alleviating stress. Some naturally occurring sounds, such as those produced by insects and bats, contain frequencies above our hearing range. This is known as ultrasound. Some research has suggested that these sounds may make our brains more alert and nervous systems more relaxed. However, we're not sure yet if including the naturally occurring ultrasound in recordings of natural environments provides these benefits. To find out, we conducted a study in which participants listened to both natural and urban sounds, with and without ultrasound, and performed tasks to assess their ability to focus. We also asked them how they felt before and after listening. The results showed that ultrasound didn't change how well people could focus or how they felt. Some people did get more mentally fatigued after doing tasks while ultrasound was playing. This is interesting because no one has ever observed this happening before. In addition, the type of soundscape environment but also especially, how appealing our participants found it, had strong effects on how they felt after listening to it. Overall, although our findings did not support all our predictions, they still provide useful information for anyone that is interested in these subjects.

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.

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Available for download on Tuesday, December 23, 2025

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