In this study, to investigate an influence of a visual stimulus presentation on auditory sensitivity, the absolute threshold of hearing was measured under conditions with and without a flash light. In the experiment, pure tones at a frequency of 500 Hz and a duration of 0.5 s were used as the test sound for the measurement of the threshold. Then, the threshold change was obtained by subtracting the threshold with a flash light from that without a flash light. As a result, the absolute threshold of hearing was decreased approximately 2.1 dB by presenting a flash light. It is, therefore, considered that the loudness of the test sound was essentially increased by presenting a flash light, or that a flash light worked to increase attention to the test sound.