It is suggested that a brief stimulus of a few seconds to a few dozen seconds provides refreshment to an intellectually engaged performers, allowing them to maintain their intellectual concentration. In this study, we conducted a cognitive task-based experiment using a combination sound of birdsong and pink noise as a stimulus to promote micro-refreshment. From the results of this experiment, we investigated and discussed the effects of sound-based micro-refresh on the concentration time ratio (CTR) and mental workload of the participants in the experiment.