▎ 摘　　要

In our living environment, there are a lot of Joule heating sources around such as machines, chips, sunlight, etc. Joule heating has always been considered a useless power except in domestic appliances. Here, we report that Joule heating could be reused by reduced graphene oxide (rGO) to emit sound. Large-area freestanding rGO is demonstrated to emit sound under different radii of curvature. Tunable sound spectrum mappings are obtained by changing the radius of curvature. It was observed that decreasing the curvature radius could provide a better sound directivity. Theoretical simulations suggest that the mechanism is related to the thermoacoustic effect. Due to the excellent characteristics of flexibility and large area, this rGO sound-emitting device will open wide applications in environmental, biomedical and many other fields.