1. A noise estimation apparatus comprising: a correlation calculator configured to calculate a correlation value of a spectrum between a plurality of frames in sound information obtained using one or more microphones; a power calculator configured to calculate a power value indicating a sound level of one target frame among the plurality of frames; an update determiner configured to determine an update degree indicating a degree to which the sound information of the target frame is to be reflected in a noise model stored in a storage, or determine whether or not the noise model is to be updated to an other noise model, based on the power value of the target frame and the correlation value; and an updater configured to generate the other noise model based on a determined result by the update determiner, the sound information of the target frame, and the noise model.