The final goal is to propose a new method to evaluate the risk of virus infection from the aspect of the sound environment. As a beginning, in this study, we tried to quantitatively grasp the effects of indoor background noise level and interpersonal distance on the speech level. A psychoacoustic experiment was conducted under a total of 20 conditions, 5 conditions for background noise level and 4 conditions for interpersonal distance, using a pair of speakers and listeners as subjects. As a result, it was found that the influence on the speech level is larger in the background noise level than in the interpersonal distance, and there is a possibility that the speech level can be predicted by the quadratic expression of the background noise level. Since the speech level in daily life conversation is about 60 dB at a background noise level of about 50 dB, it was suggested that the speaker does not make a loud voice and the listener does not have an impression of listening difficulty.