The hippocampus plays a role in encoding snapshots during daily life experiences and creating episodic memory. In the rodent, hippocampal neurons modulate their firing patterns depending on the location of the animal and collectively generate a cognitive map of space. Such internal representations regarding behavioral experience emerge and are updated through visual, auditory, olfactory, gustatory, and somatosensory information. Therefore, knowing how hippocampal neurons respond to sensory stimuli is critical; however, the current evidence is contradictory. Information about the intracellular membrane potential responses of hippocampal neurons to sensory inputs is still sparse. In the present work, we used in vivo whole-cell patch-clamp recordings from hippocampal CA1 neurons in awake mice and found that almost all hippocampal neurons exhibited a hyperpolarization of 1-2 mV immediately after the onset of a sound. This large-scale hyperpolarization was unaffected by the duration or pitch of the tone. The response was abolished by general anesthesia and a surgical fimbria-fornix lesion. In local field potentials, single sound pulses induced a phase resetting of the theta oscillations, and repetitive sound pulses at 7 Hz (theta rhythm) increased the theta oscillation power. Thus, sensory-induced hyperpolarization may segment hippocampal neural processing and render temporal boundaries in continuously ongoing experiences.