Your auditory system has its own internal “gain control” similar to a volume control on a radio or other auditory device. The level of gain determines the degree to which the environmental sounds you hear are amplified or enhanced. The level of gain changes automatically to adjust to the level of sound. Thus, as the sound level decreases, your brain increases the gain and vice versa. Gain is partially controlled by the outer hair cells in your inner ears which mechanically amplify sounds, and partially by the neural networks that respond to different levels of sound.