  Environmental noise is one of the critical issues for the observation of
gravitational waves, but is difficult to predict in advance. Therefore, to
evaluate the adverse impact of environmental noise on the detector sensitivity,
understanding the detector response to the environmental noise in actual setup
is crucial, for both the observation and future upgrades. In this paper, we
introduce and verify a new method of the environmental noise injection test
based on the post-observation commissioning of KAGRA. This new method (response
function model) includes the frequency conversion and nonlinearity of power,
which are the effects that are not considered in the current model (coupling
function model) used in LIGO and Virgo. We also confirmed the validity of our
method by applying it to an environmental noise-enriched dataset and
successfully reproducing them.
