Ambient sound has been advocated as a means for increasing the vividness of multimedia learning materials, but little research has been conducted on the subject. In this study, the Towards Utopia tangible user interface-based learning system was created to facilitate learning of sustainability concepts for 7-10 year-old children. A comparative experiment was conducted with 30 children to investigate if ambient sound enhanced learning and engagement. Half of the children used the Towards Utopia with the ambient sound mode turned on while the remaining children used the system with the ambient sound mode turned off. The experimental results showed no statistically significant difference between groups in measures of learning, enjoyment or perceived competence. However, all children showed a statistically significant increase in learning scores related to basic sustainability concepts.