1. A method comprising: characterizing, by a computing device, a speech input based on a dynamic noise adaptation (DNA) model reflecting effects of background noise; characterizing the speech input based on a null noise DNA model reflecting a null noise mismatch condition; and performing Bayesian model selection and re-weighting of the DNA model and the null noise DNA model to realize a modified DNA model characterizing the speech input for automatic speech recognition and compensating for noise to a varying degree depending on relative probabilities of the DNA model and the null noise DNA model, wherein the Bayesian model selection and re-weighting reflects a competing likelihood of which model best characterizes the speech input, and wherein re-weighting the DNA model and the null noise DNA model includes assigning zero probability to the DNA model predicted by Bayesian model averaging when the DNA model does not best characterize the speech input.